Post on 22-Feb-2016
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Reaction Rate amp Equilibrium
Collision Theory
bull When one substance is mixed with another the two substances do not react on a macroscopic basis but react as their individual particles (atoms molecules or ions) come together
bull The factors that affect how these particles come together are the factors that influence the rate of a reaction
bull In order for the reaction to occur the particles involved must collide with each other the more often the particles collide the faster the reaction occurs
bull Not every collision results in a reaction
NO3(g) + CO(g) NO2(g) + CO2(g)
bull The colliding molecules must have enough energy to react and form an activated complex
bull This minimum amount of energy is called the activation energy
bull The activated complex is the temporary arrangement of atoms as they change from reactants into products
Reaction Ratebull Is affected by the following
bull Temperaturebull Concentration of reactantsbull Particle SizeSurface Areabull Catalystsbull Nature of the Reactant
Effect of Temperature on Reaction Rate
bull Increasing the temperature increases the rate of a reaction
bull At higher temperatures the particles have more energy move faster and collide more frequently
bull More importantly the higher energy of the particles means that
bull more of the particles have sufficient energy (activation energy)
bull to have a successful collision (form an activated complex)
bull In an exothermic reaction the addition of a small amount of heat can often have a dramatic effect on the rate of reaction
bull This small addition of energy gives a few particles the activation energy they react and release more energy which is absorbed by more particles which react and release more energy hellip
Effect of Concentration on Reaction Rate
bull Increasing the concentration of the reactants increases the rate of a reaction
bull When there are more particles per unit volume they will collide more frequently causing the rate to increase
Effect of Particle SizeSurface Area
bull Decreasing particle sizeincreasing surface area increases the rate of a reaction
bull When the surface area is increases there is more contact between the reactants the number of collisions increase and therefore the rate of reaction also increases
Effect of Catalysts bull A catalyst is a substance that increases
the rate of a chemical reaction without being permanently consumed by the reaction
bull A catalyst provides a different pathway or mechanism for the reaction that has a lower activation energy
bull When the activation energy is lower more of the particles will have sufficient energy to react more of the collisions are successful therefore the reaction rate increases
A catalyst increases the rate of a reaction by lowering the activation energy
bull Effect of the Nature of the Reactant
bull The nature of the reactants involved will determine the kind of reaction that occurs
bull Reactions with bond rearrangements or electron transfer take longer than reactions without these changes
bull Ionic reactions (such as double displacement or neutralization) occur almost instantly
bull In reactions with acids stronger acids (H2SO4 HNO3 HClO4 HCl HF and HI) will occur faster than reactions with weak acids (all other acids)
bull In reactions with metals more active metals (see activity series) will react faster than less active metals
Reaction Mechanism
bull Most reactions occur in a series of steps Each step normally involves the collision of only two particles
bull There is little chance of three or more particles colliding with the proper position and sufficient energy to cause a reaction
bull If a reaction consists of several steps such as the following
bull A hellip B bull B hellip C bull C hellip final product
bull One of the steps will be slower than all the others This step is called the rate determining step
bull The other faster steps will not affect the rate of the reaction
bull The series of steps that must occur for a reaction to go to completion is called the reaction mechanism
CATALYSIS
bull middot A Catalyst is a substance that speeds up a reaction without being consumed
bull In theory the catalyst may be used over and over again
bull In practice however there is some loss of catalyst through other reactions that occur at the same time (side reactions)
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
Collision Theory
bull When one substance is mixed with another the two substances do not react on a macroscopic basis but react as their individual particles (atoms molecules or ions) come together
bull The factors that affect how these particles come together are the factors that influence the rate of a reaction
bull In order for the reaction to occur the particles involved must collide with each other the more often the particles collide the faster the reaction occurs
bull Not every collision results in a reaction
NO3(g) + CO(g) NO2(g) + CO2(g)
bull The colliding molecules must have enough energy to react and form an activated complex
bull This minimum amount of energy is called the activation energy
bull The activated complex is the temporary arrangement of atoms as they change from reactants into products
Reaction Ratebull Is affected by the following
bull Temperaturebull Concentration of reactantsbull Particle SizeSurface Areabull Catalystsbull Nature of the Reactant
Effect of Temperature on Reaction Rate
bull Increasing the temperature increases the rate of a reaction
bull At higher temperatures the particles have more energy move faster and collide more frequently
bull More importantly the higher energy of the particles means that
bull more of the particles have sufficient energy (activation energy)
bull to have a successful collision (form an activated complex)
bull In an exothermic reaction the addition of a small amount of heat can often have a dramatic effect on the rate of reaction
bull This small addition of energy gives a few particles the activation energy they react and release more energy which is absorbed by more particles which react and release more energy hellip
Effect of Concentration on Reaction Rate
bull Increasing the concentration of the reactants increases the rate of a reaction
bull When there are more particles per unit volume they will collide more frequently causing the rate to increase
Effect of Particle SizeSurface Area
bull Decreasing particle sizeincreasing surface area increases the rate of a reaction
bull When the surface area is increases there is more contact between the reactants the number of collisions increase and therefore the rate of reaction also increases
Effect of Catalysts bull A catalyst is a substance that increases
the rate of a chemical reaction without being permanently consumed by the reaction
bull A catalyst provides a different pathway or mechanism for the reaction that has a lower activation energy
bull When the activation energy is lower more of the particles will have sufficient energy to react more of the collisions are successful therefore the reaction rate increases
A catalyst increases the rate of a reaction by lowering the activation energy
bull Effect of the Nature of the Reactant
bull The nature of the reactants involved will determine the kind of reaction that occurs
bull Reactions with bond rearrangements or electron transfer take longer than reactions without these changes
bull Ionic reactions (such as double displacement or neutralization) occur almost instantly
bull In reactions with acids stronger acids (H2SO4 HNO3 HClO4 HCl HF and HI) will occur faster than reactions with weak acids (all other acids)
bull In reactions with metals more active metals (see activity series) will react faster than less active metals
Reaction Mechanism
bull Most reactions occur in a series of steps Each step normally involves the collision of only two particles
bull There is little chance of three or more particles colliding with the proper position and sufficient energy to cause a reaction
bull If a reaction consists of several steps such as the following
bull A hellip B bull B hellip C bull C hellip final product
bull One of the steps will be slower than all the others This step is called the rate determining step
bull The other faster steps will not affect the rate of the reaction
bull The series of steps that must occur for a reaction to go to completion is called the reaction mechanism
CATALYSIS
bull middot A Catalyst is a substance that speeds up a reaction without being consumed
bull In theory the catalyst may be used over and over again
bull In practice however there is some loss of catalyst through other reactions that occur at the same time (side reactions)
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
bull The factors that affect how these particles come together are the factors that influence the rate of a reaction
bull In order for the reaction to occur the particles involved must collide with each other the more often the particles collide the faster the reaction occurs
bull Not every collision results in a reaction
NO3(g) + CO(g) NO2(g) + CO2(g)
bull The colliding molecules must have enough energy to react and form an activated complex
bull This minimum amount of energy is called the activation energy
bull The activated complex is the temporary arrangement of atoms as they change from reactants into products
Reaction Ratebull Is affected by the following
bull Temperaturebull Concentration of reactantsbull Particle SizeSurface Areabull Catalystsbull Nature of the Reactant
Effect of Temperature on Reaction Rate
bull Increasing the temperature increases the rate of a reaction
bull At higher temperatures the particles have more energy move faster and collide more frequently
bull More importantly the higher energy of the particles means that
bull more of the particles have sufficient energy (activation energy)
bull to have a successful collision (form an activated complex)
bull In an exothermic reaction the addition of a small amount of heat can often have a dramatic effect on the rate of reaction
bull This small addition of energy gives a few particles the activation energy they react and release more energy which is absorbed by more particles which react and release more energy hellip
Effect of Concentration on Reaction Rate
bull Increasing the concentration of the reactants increases the rate of a reaction
bull When there are more particles per unit volume they will collide more frequently causing the rate to increase
Effect of Particle SizeSurface Area
bull Decreasing particle sizeincreasing surface area increases the rate of a reaction
bull When the surface area is increases there is more contact between the reactants the number of collisions increase and therefore the rate of reaction also increases
Effect of Catalysts bull A catalyst is a substance that increases
the rate of a chemical reaction without being permanently consumed by the reaction
bull A catalyst provides a different pathway or mechanism for the reaction that has a lower activation energy
bull When the activation energy is lower more of the particles will have sufficient energy to react more of the collisions are successful therefore the reaction rate increases
A catalyst increases the rate of a reaction by lowering the activation energy
bull Effect of the Nature of the Reactant
bull The nature of the reactants involved will determine the kind of reaction that occurs
bull Reactions with bond rearrangements or electron transfer take longer than reactions without these changes
bull Ionic reactions (such as double displacement or neutralization) occur almost instantly
bull In reactions with acids stronger acids (H2SO4 HNO3 HClO4 HCl HF and HI) will occur faster than reactions with weak acids (all other acids)
bull In reactions with metals more active metals (see activity series) will react faster than less active metals
Reaction Mechanism
bull Most reactions occur in a series of steps Each step normally involves the collision of only two particles
bull There is little chance of three or more particles colliding with the proper position and sufficient energy to cause a reaction
bull If a reaction consists of several steps such as the following
bull A hellip B bull B hellip C bull C hellip final product
bull One of the steps will be slower than all the others This step is called the rate determining step
bull The other faster steps will not affect the rate of the reaction
bull The series of steps that must occur for a reaction to go to completion is called the reaction mechanism
CATALYSIS
bull middot A Catalyst is a substance that speeds up a reaction without being consumed
bull In theory the catalyst may be used over and over again
bull In practice however there is some loss of catalyst through other reactions that occur at the same time (side reactions)
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
bull In order for the reaction to occur the particles involved must collide with each other the more often the particles collide the faster the reaction occurs
bull Not every collision results in a reaction
NO3(g) + CO(g) NO2(g) + CO2(g)
bull The colliding molecules must have enough energy to react and form an activated complex
bull This minimum amount of energy is called the activation energy
bull The activated complex is the temporary arrangement of atoms as they change from reactants into products
Reaction Ratebull Is affected by the following
bull Temperaturebull Concentration of reactantsbull Particle SizeSurface Areabull Catalystsbull Nature of the Reactant
Effect of Temperature on Reaction Rate
bull Increasing the temperature increases the rate of a reaction
bull At higher temperatures the particles have more energy move faster and collide more frequently
bull More importantly the higher energy of the particles means that
bull more of the particles have sufficient energy (activation energy)
bull to have a successful collision (form an activated complex)
bull In an exothermic reaction the addition of a small amount of heat can often have a dramatic effect on the rate of reaction
bull This small addition of energy gives a few particles the activation energy they react and release more energy which is absorbed by more particles which react and release more energy hellip
Effect of Concentration on Reaction Rate
bull Increasing the concentration of the reactants increases the rate of a reaction
bull When there are more particles per unit volume they will collide more frequently causing the rate to increase
Effect of Particle SizeSurface Area
bull Decreasing particle sizeincreasing surface area increases the rate of a reaction
bull When the surface area is increases there is more contact between the reactants the number of collisions increase and therefore the rate of reaction also increases
Effect of Catalysts bull A catalyst is a substance that increases
the rate of a chemical reaction without being permanently consumed by the reaction
bull A catalyst provides a different pathway or mechanism for the reaction that has a lower activation energy
bull When the activation energy is lower more of the particles will have sufficient energy to react more of the collisions are successful therefore the reaction rate increases
A catalyst increases the rate of a reaction by lowering the activation energy
bull Effect of the Nature of the Reactant
bull The nature of the reactants involved will determine the kind of reaction that occurs
bull Reactions with bond rearrangements or electron transfer take longer than reactions without these changes
bull Ionic reactions (such as double displacement or neutralization) occur almost instantly
bull In reactions with acids stronger acids (H2SO4 HNO3 HClO4 HCl HF and HI) will occur faster than reactions with weak acids (all other acids)
bull In reactions with metals more active metals (see activity series) will react faster than less active metals
Reaction Mechanism
bull Most reactions occur in a series of steps Each step normally involves the collision of only two particles
bull There is little chance of three or more particles colliding with the proper position and sufficient energy to cause a reaction
bull If a reaction consists of several steps such as the following
bull A hellip B bull B hellip C bull C hellip final product
bull One of the steps will be slower than all the others This step is called the rate determining step
bull The other faster steps will not affect the rate of the reaction
bull The series of steps that must occur for a reaction to go to completion is called the reaction mechanism
CATALYSIS
bull middot A Catalyst is a substance that speeds up a reaction without being consumed
bull In theory the catalyst may be used over and over again
bull In practice however there is some loss of catalyst through other reactions that occur at the same time (side reactions)
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
bull Not every collision results in a reaction
NO3(g) + CO(g) NO2(g) + CO2(g)
bull The colliding molecules must have enough energy to react and form an activated complex
bull This minimum amount of energy is called the activation energy
bull The activated complex is the temporary arrangement of atoms as they change from reactants into products
Reaction Ratebull Is affected by the following
bull Temperaturebull Concentration of reactantsbull Particle SizeSurface Areabull Catalystsbull Nature of the Reactant
Effect of Temperature on Reaction Rate
bull Increasing the temperature increases the rate of a reaction
bull At higher temperatures the particles have more energy move faster and collide more frequently
bull More importantly the higher energy of the particles means that
bull more of the particles have sufficient energy (activation energy)
bull to have a successful collision (form an activated complex)
bull In an exothermic reaction the addition of a small amount of heat can often have a dramatic effect on the rate of reaction
bull This small addition of energy gives a few particles the activation energy they react and release more energy which is absorbed by more particles which react and release more energy hellip
Effect of Concentration on Reaction Rate
bull Increasing the concentration of the reactants increases the rate of a reaction
bull When there are more particles per unit volume they will collide more frequently causing the rate to increase
Effect of Particle SizeSurface Area
bull Decreasing particle sizeincreasing surface area increases the rate of a reaction
bull When the surface area is increases there is more contact between the reactants the number of collisions increase and therefore the rate of reaction also increases
Effect of Catalysts bull A catalyst is a substance that increases
the rate of a chemical reaction without being permanently consumed by the reaction
bull A catalyst provides a different pathway or mechanism for the reaction that has a lower activation energy
bull When the activation energy is lower more of the particles will have sufficient energy to react more of the collisions are successful therefore the reaction rate increases
A catalyst increases the rate of a reaction by lowering the activation energy
bull Effect of the Nature of the Reactant
bull The nature of the reactants involved will determine the kind of reaction that occurs
bull Reactions with bond rearrangements or electron transfer take longer than reactions without these changes
bull Ionic reactions (such as double displacement or neutralization) occur almost instantly
bull In reactions with acids stronger acids (H2SO4 HNO3 HClO4 HCl HF and HI) will occur faster than reactions with weak acids (all other acids)
bull In reactions with metals more active metals (see activity series) will react faster than less active metals
Reaction Mechanism
bull Most reactions occur in a series of steps Each step normally involves the collision of only two particles
bull There is little chance of three or more particles colliding with the proper position and sufficient energy to cause a reaction
bull If a reaction consists of several steps such as the following
bull A hellip B bull B hellip C bull C hellip final product
bull One of the steps will be slower than all the others This step is called the rate determining step
bull The other faster steps will not affect the rate of the reaction
bull The series of steps that must occur for a reaction to go to completion is called the reaction mechanism
CATALYSIS
bull middot A Catalyst is a substance that speeds up a reaction without being consumed
bull In theory the catalyst may be used over and over again
bull In practice however there is some loss of catalyst through other reactions that occur at the same time (side reactions)
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
NO3(g) + CO(g) NO2(g) + CO2(g)
bull The colliding molecules must have enough energy to react and form an activated complex
bull This minimum amount of energy is called the activation energy
bull The activated complex is the temporary arrangement of atoms as they change from reactants into products
Reaction Ratebull Is affected by the following
bull Temperaturebull Concentration of reactantsbull Particle SizeSurface Areabull Catalystsbull Nature of the Reactant
Effect of Temperature on Reaction Rate
bull Increasing the temperature increases the rate of a reaction
bull At higher temperatures the particles have more energy move faster and collide more frequently
bull More importantly the higher energy of the particles means that
bull more of the particles have sufficient energy (activation energy)
bull to have a successful collision (form an activated complex)
bull In an exothermic reaction the addition of a small amount of heat can often have a dramatic effect on the rate of reaction
bull This small addition of energy gives a few particles the activation energy they react and release more energy which is absorbed by more particles which react and release more energy hellip
Effect of Concentration on Reaction Rate
bull Increasing the concentration of the reactants increases the rate of a reaction
bull When there are more particles per unit volume they will collide more frequently causing the rate to increase
Effect of Particle SizeSurface Area
bull Decreasing particle sizeincreasing surface area increases the rate of a reaction
bull When the surface area is increases there is more contact between the reactants the number of collisions increase and therefore the rate of reaction also increases
Effect of Catalysts bull A catalyst is a substance that increases
the rate of a chemical reaction without being permanently consumed by the reaction
bull A catalyst provides a different pathway or mechanism for the reaction that has a lower activation energy
bull When the activation energy is lower more of the particles will have sufficient energy to react more of the collisions are successful therefore the reaction rate increases
A catalyst increases the rate of a reaction by lowering the activation energy
bull Effect of the Nature of the Reactant
bull The nature of the reactants involved will determine the kind of reaction that occurs
bull Reactions with bond rearrangements or electron transfer take longer than reactions without these changes
bull Ionic reactions (such as double displacement or neutralization) occur almost instantly
bull In reactions with acids stronger acids (H2SO4 HNO3 HClO4 HCl HF and HI) will occur faster than reactions with weak acids (all other acids)
bull In reactions with metals more active metals (see activity series) will react faster than less active metals
Reaction Mechanism
bull Most reactions occur in a series of steps Each step normally involves the collision of only two particles
bull There is little chance of three or more particles colliding with the proper position and sufficient energy to cause a reaction
bull If a reaction consists of several steps such as the following
bull A hellip B bull B hellip C bull C hellip final product
bull One of the steps will be slower than all the others This step is called the rate determining step
bull The other faster steps will not affect the rate of the reaction
bull The series of steps that must occur for a reaction to go to completion is called the reaction mechanism
CATALYSIS
bull middot A Catalyst is a substance that speeds up a reaction without being consumed
bull In theory the catalyst may be used over and over again
bull In practice however there is some loss of catalyst through other reactions that occur at the same time (side reactions)
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
bull The colliding molecules must have enough energy to react and form an activated complex
bull This minimum amount of energy is called the activation energy
bull The activated complex is the temporary arrangement of atoms as they change from reactants into products
Reaction Ratebull Is affected by the following
bull Temperaturebull Concentration of reactantsbull Particle SizeSurface Areabull Catalystsbull Nature of the Reactant
Effect of Temperature on Reaction Rate
bull Increasing the temperature increases the rate of a reaction
bull At higher temperatures the particles have more energy move faster and collide more frequently
bull More importantly the higher energy of the particles means that
bull more of the particles have sufficient energy (activation energy)
bull to have a successful collision (form an activated complex)
bull In an exothermic reaction the addition of a small amount of heat can often have a dramatic effect on the rate of reaction
bull This small addition of energy gives a few particles the activation energy they react and release more energy which is absorbed by more particles which react and release more energy hellip
Effect of Concentration on Reaction Rate
bull Increasing the concentration of the reactants increases the rate of a reaction
bull When there are more particles per unit volume they will collide more frequently causing the rate to increase
Effect of Particle SizeSurface Area
bull Decreasing particle sizeincreasing surface area increases the rate of a reaction
bull When the surface area is increases there is more contact between the reactants the number of collisions increase and therefore the rate of reaction also increases
Effect of Catalysts bull A catalyst is a substance that increases
the rate of a chemical reaction without being permanently consumed by the reaction
bull A catalyst provides a different pathway or mechanism for the reaction that has a lower activation energy
bull When the activation energy is lower more of the particles will have sufficient energy to react more of the collisions are successful therefore the reaction rate increases
A catalyst increases the rate of a reaction by lowering the activation energy
bull Effect of the Nature of the Reactant
bull The nature of the reactants involved will determine the kind of reaction that occurs
bull Reactions with bond rearrangements or electron transfer take longer than reactions without these changes
bull Ionic reactions (such as double displacement or neutralization) occur almost instantly
bull In reactions with acids stronger acids (H2SO4 HNO3 HClO4 HCl HF and HI) will occur faster than reactions with weak acids (all other acids)
bull In reactions with metals more active metals (see activity series) will react faster than less active metals
Reaction Mechanism
bull Most reactions occur in a series of steps Each step normally involves the collision of only two particles
bull There is little chance of three or more particles colliding with the proper position and sufficient energy to cause a reaction
bull If a reaction consists of several steps such as the following
bull A hellip B bull B hellip C bull C hellip final product
bull One of the steps will be slower than all the others This step is called the rate determining step
bull The other faster steps will not affect the rate of the reaction
bull The series of steps that must occur for a reaction to go to completion is called the reaction mechanism
CATALYSIS
bull middot A Catalyst is a substance that speeds up a reaction without being consumed
bull In theory the catalyst may be used over and over again
bull In practice however there is some loss of catalyst through other reactions that occur at the same time (side reactions)
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
bull This minimum amount of energy is called the activation energy
bull The activated complex is the temporary arrangement of atoms as they change from reactants into products
Reaction Ratebull Is affected by the following
bull Temperaturebull Concentration of reactantsbull Particle SizeSurface Areabull Catalystsbull Nature of the Reactant
Effect of Temperature on Reaction Rate
bull Increasing the temperature increases the rate of a reaction
bull At higher temperatures the particles have more energy move faster and collide more frequently
bull More importantly the higher energy of the particles means that
bull more of the particles have sufficient energy (activation energy)
bull to have a successful collision (form an activated complex)
bull In an exothermic reaction the addition of a small amount of heat can often have a dramatic effect on the rate of reaction
bull This small addition of energy gives a few particles the activation energy they react and release more energy which is absorbed by more particles which react and release more energy hellip
Effect of Concentration on Reaction Rate
bull Increasing the concentration of the reactants increases the rate of a reaction
bull When there are more particles per unit volume they will collide more frequently causing the rate to increase
Effect of Particle SizeSurface Area
bull Decreasing particle sizeincreasing surface area increases the rate of a reaction
bull When the surface area is increases there is more contact between the reactants the number of collisions increase and therefore the rate of reaction also increases
Effect of Catalysts bull A catalyst is a substance that increases
the rate of a chemical reaction without being permanently consumed by the reaction
bull A catalyst provides a different pathway or mechanism for the reaction that has a lower activation energy
bull When the activation energy is lower more of the particles will have sufficient energy to react more of the collisions are successful therefore the reaction rate increases
A catalyst increases the rate of a reaction by lowering the activation energy
bull Effect of the Nature of the Reactant
bull The nature of the reactants involved will determine the kind of reaction that occurs
bull Reactions with bond rearrangements or electron transfer take longer than reactions without these changes
bull Ionic reactions (such as double displacement or neutralization) occur almost instantly
bull In reactions with acids stronger acids (H2SO4 HNO3 HClO4 HCl HF and HI) will occur faster than reactions with weak acids (all other acids)
bull In reactions with metals more active metals (see activity series) will react faster than less active metals
Reaction Mechanism
bull Most reactions occur in a series of steps Each step normally involves the collision of only two particles
bull There is little chance of three or more particles colliding with the proper position and sufficient energy to cause a reaction
bull If a reaction consists of several steps such as the following
bull A hellip B bull B hellip C bull C hellip final product
bull One of the steps will be slower than all the others This step is called the rate determining step
bull The other faster steps will not affect the rate of the reaction
bull The series of steps that must occur for a reaction to go to completion is called the reaction mechanism
CATALYSIS
bull middot A Catalyst is a substance that speeds up a reaction without being consumed
bull In theory the catalyst may be used over and over again
bull In practice however there is some loss of catalyst through other reactions that occur at the same time (side reactions)
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
bull The activated complex is the temporary arrangement of atoms as they change from reactants into products
Reaction Ratebull Is affected by the following
bull Temperaturebull Concentration of reactantsbull Particle SizeSurface Areabull Catalystsbull Nature of the Reactant
Effect of Temperature on Reaction Rate
bull Increasing the temperature increases the rate of a reaction
bull At higher temperatures the particles have more energy move faster and collide more frequently
bull More importantly the higher energy of the particles means that
bull more of the particles have sufficient energy (activation energy)
bull to have a successful collision (form an activated complex)
bull In an exothermic reaction the addition of a small amount of heat can often have a dramatic effect on the rate of reaction
bull This small addition of energy gives a few particles the activation energy they react and release more energy which is absorbed by more particles which react and release more energy hellip
Effect of Concentration on Reaction Rate
bull Increasing the concentration of the reactants increases the rate of a reaction
bull When there are more particles per unit volume they will collide more frequently causing the rate to increase
Effect of Particle SizeSurface Area
bull Decreasing particle sizeincreasing surface area increases the rate of a reaction
bull When the surface area is increases there is more contact between the reactants the number of collisions increase and therefore the rate of reaction also increases
Effect of Catalysts bull A catalyst is a substance that increases
the rate of a chemical reaction without being permanently consumed by the reaction
bull A catalyst provides a different pathway or mechanism for the reaction that has a lower activation energy
bull When the activation energy is lower more of the particles will have sufficient energy to react more of the collisions are successful therefore the reaction rate increases
A catalyst increases the rate of a reaction by lowering the activation energy
bull Effect of the Nature of the Reactant
bull The nature of the reactants involved will determine the kind of reaction that occurs
bull Reactions with bond rearrangements or electron transfer take longer than reactions without these changes
bull Ionic reactions (such as double displacement or neutralization) occur almost instantly
bull In reactions with acids stronger acids (H2SO4 HNO3 HClO4 HCl HF and HI) will occur faster than reactions with weak acids (all other acids)
bull In reactions with metals more active metals (see activity series) will react faster than less active metals
Reaction Mechanism
bull Most reactions occur in a series of steps Each step normally involves the collision of only two particles
bull There is little chance of three or more particles colliding with the proper position and sufficient energy to cause a reaction
bull If a reaction consists of several steps such as the following
bull A hellip B bull B hellip C bull C hellip final product
bull One of the steps will be slower than all the others This step is called the rate determining step
bull The other faster steps will not affect the rate of the reaction
bull The series of steps that must occur for a reaction to go to completion is called the reaction mechanism
CATALYSIS
bull middot A Catalyst is a substance that speeds up a reaction without being consumed
bull In theory the catalyst may be used over and over again
bull In practice however there is some loss of catalyst through other reactions that occur at the same time (side reactions)
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
Reaction Ratebull Is affected by the following
bull Temperaturebull Concentration of reactantsbull Particle SizeSurface Areabull Catalystsbull Nature of the Reactant
Effect of Temperature on Reaction Rate
bull Increasing the temperature increases the rate of a reaction
bull At higher temperatures the particles have more energy move faster and collide more frequently
bull More importantly the higher energy of the particles means that
bull more of the particles have sufficient energy (activation energy)
bull to have a successful collision (form an activated complex)
bull In an exothermic reaction the addition of a small amount of heat can often have a dramatic effect on the rate of reaction
bull This small addition of energy gives a few particles the activation energy they react and release more energy which is absorbed by more particles which react and release more energy hellip
Effect of Concentration on Reaction Rate
bull Increasing the concentration of the reactants increases the rate of a reaction
bull When there are more particles per unit volume they will collide more frequently causing the rate to increase
Effect of Particle SizeSurface Area
bull Decreasing particle sizeincreasing surface area increases the rate of a reaction
bull When the surface area is increases there is more contact between the reactants the number of collisions increase and therefore the rate of reaction also increases
Effect of Catalysts bull A catalyst is a substance that increases
the rate of a chemical reaction without being permanently consumed by the reaction
bull A catalyst provides a different pathway or mechanism for the reaction that has a lower activation energy
bull When the activation energy is lower more of the particles will have sufficient energy to react more of the collisions are successful therefore the reaction rate increases
A catalyst increases the rate of a reaction by lowering the activation energy
bull Effect of the Nature of the Reactant
bull The nature of the reactants involved will determine the kind of reaction that occurs
bull Reactions with bond rearrangements or electron transfer take longer than reactions without these changes
bull Ionic reactions (such as double displacement or neutralization) occur almost instantly
bull In reactions with acids stronger acids (H2SO4 HNO3 HClO4 HCl HF and HI) will occur faster than reactions with weak acids (all other acids)
bull In reactions with metals more active metals (see activity series) will react faster than less active metals
Reaction Mechanism
bull Most reactions occur in a series of steps Each step normally involves the collision of only two particles
bull There is little chance of three or more particles colliding with the proper position and sufficient energy to cause a reaction
bull If a reaction consists of several steps such as the following
bull A hellip B bull B hellip C bull C hellip final product
bull One of the steps will be slower than all the others This step is called the rate determining step
bull The other faster steps will not affect the rate of the reaction
bull The series of steps that must occur for a reaction to go to completion is called the reaction mechanism
CATALYSIS
bull middot A Catalyst is a substance that speeds up a reaction without being consumed
bull In theory the catalyst may be used over and over again
bull In practice however there is some loss of catalyst through other reactions that occur at the same time (side reactions)
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
Effect of Temperature on Reaction Rate
bull Increasing the temperature increases the rate of a reaction
bull At higher temperatures the particles have more energy move faster and collide more frequently
bull More importantly the higher energy of the particles means that
bull more of the particles have sufficient energy (activation energy)
bull to have a successful collision (form an activated complex)
bull In an exothermic reaction the addition of a small amount of heat can often have a dramatic effect on the rate of reaction
bull This small addition of energy gives a few particles the activation energy they react and release more energy which is absorbed by more particles which react and release more energy hellip
Effect of Concentration on Reaction Rate
bull Increasing the concentration of the reactants increases the rate of a reaction
bull When there are more particles per unit volume they will collide more frequently causing the rate to increase
Effect of Particle SizeSurface Area
bull Decreasing particle sizeincreasing surface area increases the rate of a reaction
bull When the surface area is increases there is more contact between the reactants the number of collisions increase and therefore the rate of reaction also increases
Effect of Catalysts bull A catalyst is a substance that increases
the rate of a chemical reaction without being permanently consumed by the reaction
bull A catalyst provides a different pathway or mechanism for the reaction that has a lower activation energy
bull When the activation energy is lower more of the particles will have sufficient energy to react more of the collisions are successful therefore the reaction rate increases
A catalyst increases the rate of a reaction by lowering the activation energy
bull Effect of the Nature of the Reactant
bull The nature of the reactants involved will determine the kind of reaction that occurs
bull Reactions with bond rearrangements or electron transfer take longer than reactions without these changes
bull Ionic reactions (such as double displacement or neutralization) occur almost instantly
bull In reactions with acids stronger acids (H2SO4 HNO3 HClO4 HCl HF and HI) will occur faster than reactions with weak acids (all other acids)
bull In reactions with metals more active metals (see activity series) will react faster than less active metals
Reaction Mechanism
bull Most reactions occur in a series of steps Each step normally involves the collision of only two particles
bull There is little chance of three or more particles colliding with the proper position and sufficient energy to cause a reaction
bull If a reaction consists of several steps such as the following
bull A hellip B bull B hellip C bull C hellip final product
bull One of the steps will be slower than all the others This step is called the rate determining step
bull The other faster steps will not affect the rate of the reaction
bull The series of steps that must occur for a reaction to go to completion is called the reaction mechanism
CATALYSIS
bull middot A Catalyst is a substance that speeds up a reaction without being consumed
bull In theory the catalyst may be used over and over again
bull In practice however there is some loss of catalyst through other reactions that occur at the same time (side reactions)
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
bull At higher temperatures the particles have more energy move faster and collide more frequently
bull More importantly the higher energy of the particles means that
bull more of the particles have sufficient energy (activation energy)
bull to have a successful collision (form an activated complex)
bull In an exothermic reaction the addition of a small amount of heat can often have a dramatic effect on the rate of reaction
bull This small addition of energy gives a few particles the activation energy they react and release more energy which is absorbed by more particles which react and release more energy hellip
Effect of Concentration on Reaction Rate
bull Increasing the concentration of the reactants increases the rate of a reaction
bull When there are more particles per unit volume they will collide more frequently causing the rate to increase
Effect of Particle SizeSurface Area
bull Decreasing particle sizeincreasing surface area increases the rate of a reaction
bull When the surface area is increases there is more contact between the reactants the number of collisions increase and therefore the rate of reaction also increases
Effect of Catalysts bull A catalyst is a substance that increases
the rate of a chemical reaction without being permanently consumed by the reaction
bull A catalyst provides a different pathway or mechanism for the reaction that has a lower activation energy
bull When the activation energy is lower more of the particles will have sufficient energy to react more of the collisions are successful therefore the reaction rate increases
A catalyst increases the rate of a reaction by lowering the activation energy
bull Effect of the Nature of the Reactant
bull The nature of the reactants involved will determine the kind of reaction that occurs
bull Reactions with bond rearrangements or electron transfer take longer than reactions without these changes
bull Ionic reactions (such as double displacement or neutralization) occur almost instantly
bull In reactions with acids stronger acids (H2SO4 HNO3 HClO4 HCl HF and HI) will occur faster than reactions with weak acids (all other acids)
bull In reactions with metals more active metals (see activity series) will react faster than less active metals
Reaction Mechanism
bull Most reactions occur in a series of steps Each step normally involves the collision of only two particles
bull There is little chance of three or more particles colliding with the proper position and sufficient energy to cause a reaction
bull If a reaction consists of several steps such as the following
bull A hellip B bull B hellip C bull C hellip final product
bull One of the steps will be slower than all the others This step is called the rate determining step
bull The other faster steps will not affect the rate of the reaction
bull The series of steps that must occur for a reaction to go to completion is called the reaction mechanism
CATALYSIS
bull middot A Catalyst is a substance that speeds up a reaction without being consumed
bull In theory the catalyst may be used over and over again
bull In practice however there is some loss of catalyst through other reactions that occur at the same time (side reactions)
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
bull More importantly the higher energy of the particles means that
bull more of the particles have sufficient energy (activation energy)
bull to have a successful collision (form an activated complex)
bull In an exothermic reaction the addition of a small amount of heat can often have a dramatic effect on the rate of reaction
bull This small addition of energy gives a few particles the activation energy they react and release more energy which is absorbed by more particles which react and release more energy hellip
Effect of Concentration on Reaction Rate
bull Increasing the concentration of the reactants increases the rate of a reaction
bull When there are more particles per unit volume they will collide more frequently causing the rate to increase
Effect of Particle SizeSurface Area
bull Decreasing particle sizeincreasing surface area increases the rate of a reaction
bull When the surface area is increases there is more contact between the reactants the number of collisions increase and therefore the rate of reaction also increases
Effect of Catalysts bull A catalyst is a substance that increases
the rate of a chemical reaction without being permanently consumed by the reaction
bull A catalyst provides a different pathway or mechanism for the reaction that has a lower activation energy
bull When the activation energy is lower more of the particles will have sufficient energy to react more of the collisions are successful therefore the reaction rate increases
A catalyst increases the rate of a reaction by lowering the activation energy
bull Effect of the Nature of the Reactant
bull The nature of the reactants involved will determine the kind of reaction that occurs
bull Reactions with bond rearrangements or electron transfer take longer than reactions without these changes
bull Ionic reactions (such as double displacement or neutralization) occur almost instantly
bull In reactions with acids stronger acids (H2SO4 HNO3 HClO4 HCl HF and HI) will occur faster than reactions with weak acids (all other acids)
bull In reactions with metals more active metals (see activity series) will react faster than less active metals
Reaction Mechanism
bull Most reactions occur in a series of steps Each step normally involves the collision of only two particles
bull There is little chance of three or more particles colliding with the proper position and sufficient energy to cause a reaction
bull If a reaction consists of several steps such as the following
bull A hellip B bull B hellip C bull C hellip final product
bull One of the steps will be slower than all the others This step is called the rate determining step
bull The other faster steps will not affect the rate of the reaction
bull The series of steps that must occur for a reaction to go to completion is called the reaction mechanism
CATALYSIS
bull middot A Catalyst is a substance that speeds up a reaction without being consumed
bull In theory the catalyst may be used over and over again
bull In practice however there is some loss of catalyst through other reactions that occur at the same time (side reactions)
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
bull In an exothermic reaction the addition of a small amount of heat can often have a dramatic effect on the rate of reaction
bull This small addition of energy gives a few particles the activation energy they react and release more energy which is absorbed by more particles which react and release more energy hellip
Effect of Concentration on Reaction Rate
bull Increasing the concentration of the reactants increases the rate of a reaction
bull When there are more particles per unit volume they will collide more frequently causing the rate to increase
Effect of Particle SizeSurface Area
bull Decreasing particle sizeincreasing surface area increases the rate of a reaction
bull When the surface area is increases there is more contact between the reactants the number of collisions increase and therefore the rate of reaction also increases
Effect of Catalysts bull A catalyst is a substance that increases
the rate of a chemical reaction without being permanently consumed by the reaction
bull A catalyst provides a different pathway or mechanism for the reaction that has a lower activation energy
bull When the activation energy is lower more of the particles will have sufficient energy to react more of the collisions are successful therefore the reaction rate increases
A catalyst increases the rate of a reaction by lowering the activation energy
bull Effect of the Nature of the Reactant
bull The nature of the reactants involved will determine the kind of reaction that occurs
bull Reactions with bond rearrangements or electron transfer take longer than reactions without these changes
bull Ionic reactions (such as double displacement or neutralization) occur almost instantly
bull In reactions with acids stronger acids (H2SO4 HNO3 HClO4 HCl HF and HI) will occur faster than reactions with weak acids (all other acids)
bull In reactions with metals more active metals (see activity series) will react faster than less active metals
Reaction Mechanism
bull Most reactions occur in a series of steps Each step normally involves the collision of only two particles
bull There is little chance of three or more particles colliding with the proper position and sufficient energy to cause a reaction
bull If a reaction consists of several steps such as the following
bull A hellip B bull B hellip C bull C hellip final product
bull One of the steps will be slower than all the others This step is called the rate determining step
bull The other faster steps will not affect the rate of the reaction
bull The series of steps that must occur for a reaction to go to completion is called the reaction mechanism
CATALYSIS
bull middot A Catalyst is a substance that speeds up a reaction without being consumed
bull In theory the catalyst may be used over and over again
bull In practice however there is some loss of catalyst through other reactions that occur at the same time (side reactions)
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
bull This small addition of energy gives a few particles the activation energy they react and release more energy which is absorbed by more particles which react and release more energy hellip
Effect of Concentration on Reaction Rate
bull Increasing the concentration of the reactants increases the rate of a reaction
bull When there are more particles per unit volume they will collide more frequently causing the rate to increase
Effect of Particle SizeSurface Area
bull Decreasing particle sizeincreasing surface area increases the rate of a reaction
bull When the surface area is increases there is more contact between the reactants the number of collisions increase and therefore the rate of reaction also increases
Effect of Catalysts bull A catalyst is a substance that increases
the rate of a chemical reaction without being permanently consumed by the reaction
bull A catalyst provides a different pathway or mechanism for the reaction that has a lower activation energy
bull When the activation energy is lower more of the particles will have sufficient energy to react more of the collisions are successful therefore the reaction rate increases
A catalyst increases the rate of a reaction by lowering the activation energy
bull Effect of the Nature of the Reactant
bull The nature of the reactants involved will determine the kind of reaction that occurs
bull Reactions with bond rearrangements or electron transfer take longer than reactions without these changes
bull Ionic reactions (such as double displacement or neutralization) occur almost instantly
bull In reactions with acids stronger acids (H2SO4 HNO3 HClO4 HCl HF and HI) will occur faster than reactions with weak acids (all other acids)
bull In reactions with metals more active metals (see activity series) will react faster than less active metals
Reaction Mechanism
bull Most reactions occur in a series of steps Each step normally involves the collision of only two particles
bull There is little chance of three or more particles colliding with the proper position and sufficient energy to cause a reaction
bull If a reaction consists of several steps such as the following
bull A hellip B bull B hellip C bull C hellip final product
bull One of the steps will be slower than all the others This step is called the rate determining step
bull The other faster steps will not affect the rate of the reaction
bull The series of steps that must occur for a reaction to go to completion is called the reaction mechanism
CATALYSIS
bull middot A Catalyst is a substance that speeds up a reaction without being consumed
bull In theory the catalyst may be used over and over again
bull In practice however there is some loss of catalyst through other reactions that occur at the same time (side reactions)
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
Effect of Concentration on Reaction Rate
bull Increasing the concentration of the reactants increases the rate of a reaction
bull When there are more particles per unit volume they will collide more frequently causing the rate to increase
Effect of Particle SizeSurface Area
bull Decreasing particle sizeincreasing surface area increases the rate of a reaction
bull When the surface area is increases there is more contact between the reactants the number of collisions increase and therefore the rate of reaction also increases
Effect of Catalysts bull A catalyst is a substance that increases
the rate of a chemical reaction without being permanently consumed by the reaction
bull A catalyst provides a different pathway or mechanism for the reaction that has a lower activation energy
bull When the activation energy is lower more of the particles will have sufficient energy to react more of the collisions are successful therefore the reaction rate increases
A catalyst increases the rate of a reaction by lowering the activation energy
bull Effect of the Nature of the Reactant
bull The nature of the reactants involved will determine the kind of reaction that occurs
bull Reactions with bond rearrangements or electron transfer take longer than reactions without these changes
bull Ionic reactions (such as double displacement or neutralization) occur almost instantly
bull In reactions with acids stronger acids (H2SO4 HNO3 HClO4 HCl HF and HI) will occur faster than reactions with weak acids (all other acids)
bull In reactions with metals more active metals (see activity series) will react faster than less active metals
Reaction Mechanism
bull Most reactions occur in a series of steps Each step normally involves the collision of only two particles
bull There is little chance of three or more particles colliding with the proper position and sufficient energy to cause a reaction
bull If a reaction consists of several steps such as the following
bull A hellip B bull B hellip C bull C hellip final product
bull One of the steps will be slower than all the others This step is called the rate determining step
bull The other faster steps will not affect the rate of the reaction
bull The series of steps that must occur for a reaction to go to completion is called the reaction mechanism
CATALYSIS
bull middot A Catalyst is a substance that speeds up a reaction without being consumed
bull In theory the catalyst may be used over and over again
bull In practice however there is some loss of catalyst through other reactions that occur at the same time (side reactions)
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
Effect of Particle SizeSurface Area
bull Decreasing particle sizeincreasing surface area increases the rate of a reaction
bull When the surface area is increases there is more contact between the reactants the number of collisions increase and therefore the rate of reaction also increases
Effect of Catalysts bull A catalyst is a substance that increases
the rate of a chemical reaction without being permanently consumed by the reaction
bull A catalyst provides a different pathway or mechanism for the reaction that has a lower activation energy
bull When the activation energy is lower more of the particles will have sufficient energy to react more of the collisions are successful therefore the reaction rate increases
A catalyst increases the rate of a reaction by lowering the activation energy
bull Effect of the Nature of the Reactant
bull The nature of the reactants involved will determine the kind of reaction that occurs
bull Reactions with bond rearrangements or electron transfer take longer than reactions without these changes
bull Ionic reactions (such as double displacement or neutralization) occur almost instantly
bull In reactions with acids stronger acids (H2SO4 HNO3 HClO4 HCl HF and HI) will occur faster than reactions with weak acids (all other acids)
bull In reactions with metals more active metals (see activity series) will react faster than less active metals
Reaction Mechanism
bull Most reactions occur in a series of steps Each step normally involves the collision of only two particles
bull There is little chance of three or more particles colliding with the proper position and sufficient energy to cause a reaction
bull If a reaction consists of several steps such as the following
bull A hellip B bull B hellip C bull C hellip final product
bull One of the steps will be slower than all the others This step is called the rate determining step
bull The other faster steps will not affect the rate of the reaction
bull The series of steps that must occur for a reaction to go to completion is called the reaction mechanism
CATALYSIS
bull middot A Catalyst is a substance that speeds up a reaction without being consumed
bull In theory the catalyst may be used over and over again
bull In practice however there is some loss of catalyst through other reactions that occur at the same time (side reactions)
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
Effect of Catalysts bull A catalyst is a substance that increases
the rate of a chemical reaction without being permanently consumed by the reaction
bull A catalyst provides a different pathway or mechanism for the reaction that has a lower activation energy
bull When the activation energy is lower more of the particles will have sufficient energy to react more of the collisions are successful therefore the reaction rate increases
A catalyst increases the rate of a reaction by lowering the activation energy
bull Effect of the Nature of the Reactant
bull The nature of the reactants involved will determine the kind of reaction that occurs
bull Reactions with bond rearrangements or electron transfer take longer than reactions without these changes
bull Ionic reactions (such as double displacement or neutralization) occur almost instantly
bull In reactions with acids stronger acids (H2SO4 HNO3 HClO4 HCl HF and HI) will occur faster than reactions with weak acids (all other acids)
bull In reactions with metals more active metals (see activity series) will react faster than less active metals
Reaction Mechanism
bull Most reactions occur in a series of steps Each step normally involves the collision of only two particles
bull There is little chance of three or more particles colliding with the proper position and sufficient energy to cause a reaction
bull If a reaction consists of several steps such as the following
bull A hellip B bull B hellip C bull C hellip final product
bull One of the steps will be slower than all the others This step is called the rate determining step
bull The other faster steps will not affect the rate of the reaction
bull The series of steps that must occur for a reaction to go to completion is called the reaction mechanism
CATALYSIS
bull middot A Catalyst is a substance that speeds up a reaction without being consumed
bull In theory the catalyst may be used over and over again
bull In practice however there is some loss of catalyst through other reactions that occur at the same time (side reactions)
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
bull A catalyst provides a different pathway or mechanism for the reaction that has a lower activation energy
bull When the activation energy is lower more of the particles will have sufficient energy to react more of the collisions are successful therefore the reaction rate increases
A catalyst increases the rate of a reaction by lowering the activation energy
bull Effect of the Nature of the Reactant
bull The nature of the reactants involved will determine the kind of reaction that occurs
bull Reactions with bond rearrangements or electron transfer take longer than reactions without these changes
bull Ionic reactions (such as double displacement or neutralization) occur almost instantly
bull In reactions with acids stronger acids (H2SO4 HNO3 HClO4 HCl HF and HI) will occur faster than reactions with weak acids (all other acids)
bull In reactions with metals more active metals (see activity series) will react faster than less active metals
Reaction Mechanism
bull Most reactions occur in a series of steps Each step normally involves the collision of only two particles
bull There is little chance of three or more particles colliding with the proper position and sufficient energy to cause a reaction
bull If a reaction consists of several steps such as the following
bull A hellip B bull B hellip C bull C hellip final product
bull One of the steps will be slower than all the others This step is called the rate determining step
bull The other faster steps will not affect the rate of the reaction
bull The series of steps that must occur for a reaction to go to completion is called the reaction mechanism
CATALYSIS
bull middot A Catalyst is a substance that speeds up a reaction without being consumed
bull In theory the catalyst may be used over and over again
bull In practice however there is some loss of catalyst through other reactions that occur at the same time (side reactions)
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
A catalyst increases the rate of a reaction by lowering the activation energy
bull Effect of the Nature of the Reactant
bull The nature of the reactants involved will determine the kind of reaction that occurs
bull Reactions with bond rearrangements or electron transfer take longer than reactions without these changes
bull Ionic reactions (such as double displacement or neutralization) occur almost instantly
bull In reactions with acids stronger acids (H2SO4 HNO3 HClO4 HCl HF and HI) will occur faster than reactions with weak acids (all other acids)
bull In reactions with metals more active metals (see activity series) will react faster than less active metals
Reaction Mechanism
bull Most reactions occur in a series of steps Each step normally involves the collision of only two particles
bull There is little chance of three or more particles colliding with the proper position and sufficient energy to cause a reaction
bull If a reaction consists of several steps such as the following
bull A hellip B bull B hellip C bull C hellip final product
bull One of the steps will be slower than all the others This step is called the rate determining step
bull The other faster steps will not affect the rate of the reaction
bull The series of steps that must occur for a reaction to go to completion is called the reaction mechanism
CATALYSIS
bull middot A Catalyst is a substance that speeds up a reaction without being consumed
bull In theory the catalyst may be used over and over again
bull In practice however there is some loss of catalyst through other reactions that occur at the same time (side reactions)
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
bull Effect of the Nature of the Reactant
bull The nature of the reactants involved will determine the kind of reaction that occurs
bull Reactions with bond rearrangements or electron transfer take longer than reactions without these changes
bull Ionic reactions (such as double displacement or neutralization) occur almost instantly
bull In reactions with acids stronger acids (H2SO4 HNO3 HClO4 HCl HF and HI) will occur faster than reactions with weak acids (all other acids)
bull In reactions with metals more active metals (see activity series) will react faster than less active metals
Reaction Mechanism
bull Most reactions occur in a series of steps Each step normally involves the collision of only two particles
bull There is little chance of three or more particles colliding with the proper position and sufficient energy to cause a reaction
bull If a reaction consists of several steps such as the following
bull A hellip B bull B hellip C bull C hellip final product
bull One of the steps will be slower than all the others This step is called the rate determining step
bull The other faster steps will not affect the rate of the reaction
bull The series of steps that must occur for a reaction to go to completion is called the reaction mechanism
CATALYSIS
bull middot A Catalyst is a substance that speeds up a reaction without being consumed
bull In theory the catalyst may be used over and over again
bull In practice however there is some loss of catalyst through other reactions that occur at the same time (side reactions)
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
bull Reactions with bond rearrangements or electron transfer take longer than reactions without these changes
bull Ionic reactions (such as double displacement or neutralization) occur almost instantly
bull In reactions with acids stronger acids (H2SO4 HNO3 HClO4 HCl HF and HI) will occur faster than reactions with weak acids (all other acids)
bull In reactions with metals more active metals (see activity series) will react faster than less active metals
Reaction Mechanism
bull Most reactions occur in a series of steps Each step normally involves the collision of only two particles
bull There is little chance of three or more particles colliding with the proper position and sufficient energy to cause a reaction
bull If a reaction consists of several steps such as the following
bull A hellip B bull B hellip C bull C hellip final product
bull One of the steps will be slower than all the others This step is called the rate determining step
bull The other faster steps will not affect the rate of the reaction
bull The series of steps that must occur for a reaction to go to completion is called the reaction mechanism
CATALYSIS
bull middot A Catalyst is a substance that speeds up a reaction without being consumed
bull In theory the catalyst may be used over and over again
bull In practice however there is some loss of catalyst through other reactions that occur at the same time (side reactions)
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
bull In reactions with acids stronger acids (H2SO4 HNO3 HClO4 HCl HF and HI) will occur faster than reactions with weak acids (all other acids)
bull In reactions with metals more active metals (see activity series) will react faster than less active metals
Reaction Mechanism
bull Most reactions occur in a series of steps Each step normally involves the collision of only two particles
bull There is little chance of three or more particles colliding with the proper position and sufficient energy to cause a reaction
bull If a reaction consists of several steps such as the following
bull A hellip B bull B hellip C bull C hellip final product
bull One of the steps will be slower than all the others This step is called the rate determining step
bull The other faster steps will not affect the rate of the reaction
bull The series of steps that must occur for a reaction to go to completion is called the reaction mechanism
CATALYSIS
bull middot A Catalyst is a substance that speeds up a reaction without being consumed
bull In theory the catalyst may be used over and over again
bull In practice however there is some loss of catalyst through other reactions that occur at the same time (side reactions)
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
bull In reactions with metals more active metals (see activity series) will react faster than less active metals
Reaction Mechanism
bull Most reactions occur in a series of steps Each step normally involves the collision of only two particles
bull There is little chance of three or more particles colliding with the proper position and sufficient energy to cause a reaction
bull If a reaction consists of several steps such as the following
bull A hellip B bull B hellip C bull C hellip final product
bull One of the steps will be slower than all the others This step is called the rate determining step
bull The other faster steps will not affect the rate of the reaction
bull The series of steps that must occur for a reaction to go to completion is called the reaction mechanism
CATALYSIS
bull middot A Catalyst is a substance that speeds up a reaction without being consumed
bull In theory the catalyst may be used over and over again
bull In practice however there is some loss of catalyst through other reactions that occur at the same time (side reactions)
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
Reaction Mechanism
bull Most reactions occur in a series of steps Each step normally involves the collision of only two particles
bull There is little chance of three or more particles colliding with the proper position and sufficient energy to cause a reaction
bull If a reaction consists of several steps such as the following
bull A hellip B bull B hellip C bull C hellip final product
bull One of the steps will be slower than all the others This step is called the rate determining step
bull The other faster steps will not affect the rate of the reaction
bull The series of steps that must occur for a reaction to go to completion is called the reaction mechanism
CATALYSIS
bull middot A Catalyst is a substance that speeds up a reaction without being consumed
bull In theory the catalyst may be used over and over again
bull In practice however there is some loss of catalyst through other reactions that occur at the same time (side reactions)
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
bull There is little chance of three or more particles colliding with the proper position and sufficient energy to cause a reaction
bull If a reaction consists of several steps such as the following
bull A hellip B bull B hellip C bull C hellip final product
bull One of the steps will be slower than all the others This step is called the rate determining step
bull The other faster steps will not affect the rate of the reaction
bull The series of steps that must occur for a reaction to go to completion is called the reaction mechanism
CATALYSIS
bull middot A Catalyst is a substance that speeds up a reaction without being consumed
bull In theory the catalyst may be used over and over again
bull In practice however there is some loss of catalyst through other reactions that occur at the same time (side reactions)
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
bull If a reaction consists of several steps such as the following
bull A hellip B bull B hellip C bull C hellip final product
bull One of the steps will be slower than all the others This step is called the rate determining step
bull The other faster steps will not affect the rate of the reaction
bull The series of steps that must occur for a reaction to go to completion is called the reaction mechanism
CATALYSIS
bull middot A Catalyst is a substance that speeds up a reaction without being consumed
bull In theory the catalyst may be used over and over again
bull In practice however there is some loss of catalyst through other reactions that occur at the same time (side reactions)
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
bull One of the steps will be slower than all the others This step is called the rate determining step
bull The other faster steps will not affect the rate of the reaction
bull The series of steps that must occur for a reaction to go to completion is called the reaction mechanism
CATALYSIS
bull middot A Catalyst is a substance that speeds up a reaction without being consumed
bull In theory the catalyst may be used over and over again
bull In practice however there is some loss of catalyst through other reactions that occur at the same time (side reactions)
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
bull The series of steps that must occur for a reaction to go to completion is called the reaction mechanism
CATALYSIS
bull middot A Catalyst is a substance that speeds up a reaction without being consumed
bull In theory the catalyst may be used over and over again
bull In practice however there is some loss of catalyst through other reactions that occur at the same time (side reactions)
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
CATALYSIS
bull middot A Catalyst is a substance that speeds up a reaction without being consumed
bull In theory the catalyst may be used over and over again
bull In practice however there is some loss of catalyst through other reactions that occur at the same time (side reactions)
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
bull In theory the catalyst may be used over and over again
bull In practice however there is some loss of catalyst through other reactions that occur at the same time (side reactions)
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
bull In practice however there is some loss of catalyst through other reactions that occur at the same time (side reactions)
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
Importance of Catalysts
bull middot Catalysts allow reactions to occur much faster
bull middot Catalysts allow reactions to occur at lower temperatures (energy savings)
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
Characteristics of Catalysts
bull Catalysts are often quite specific They increase the rate of some reactions but not others
bull Enzymes (catalysts used in biological organisms) are extremely selective
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
How Catalysts Work
bull A catalyst is an active participant in the reaction
bull A catalyst must participate in one step of a reaction and be regenerated in a later step
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
bull The catalyzed reaction mechanism makes available a reaction path having an increased
bull overall rate of reaction by - increasing the frequency factor or - decreasing the Activation Energy Ea
(most dramatic effect)
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
ExampleThe commercial preparation of sulfuric
acid H2SO4 from SO2 NO catalyst
First step 2 SO2 g) + O2(g) 2 SO3(g)
Proposed Mechanismbull 2NO + O2 2 NO2bull NO2 + SO2 NO + SO3 (must occur twice each time the first step
occurs once)
bull catalystbull 2NO + O2 2NO2 reaction intermediate
bull 2NO2 + 2SO2 2NO + 2SO3 ___________________________________
Overall 2 SO2 + O2 2SO3
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
Equilibrium Systems
bull In some chemical reactions all of the reactants are converted to products
2Cu(s) + O2(g) 2CuO(s)
This reaction is said to go to completion
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
bull In other processes however the final mixture consists of both products and reactants
Reactants Products Reactants Products Reactants ProductsThis reaction is at equilibrium
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
The reactants are colliding to form products while the products are also colliding to reform reactants
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
bull This is known as a dynamic equilibrium ndash the rate of the forward reaction is equal to the rate of the reverse reaction
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
bull Equilibrium is reached in a closed system when all properties of the system are constant
bull The forward and reverse reactions are happening at the same rate
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
The concentrations of products and reactants may be different but they are no longer changing
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
Le Chacirctelierrsquos Principle
bull If a stress is applied to a system at equilibrium the equilibrium will shift to relieve the stress
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
bull Concentration ndash Increase [reactant] = shifts to use up the
added reactants and produce more products bull 1048766 Shifts right
ndash Increase [product] = shifts to use up added product and product more reactants
bull 1048766 Shifts left ndash Decrease [reactant] = shifts to produce more
reactants bull 1048766 Shifts left
ndash Decrease [product] = shifts to produce more products
bull 1048766 Shifts right
bull bull bull bull bull
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
bull Temperature ndash Increase = favours the endothermic direction
bull 1048766 The reaction shifts in the direction that uses up the added energy
ndash Decreasing = favours the exothermic direction
bull 1048766 The reaction shifts in the direction that produces energy
bull bull bull
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
bull PressureVolume ndash Increasing pressureDecreasing volume
favours fewer gas molecules bull 1048766 The reaction shifts to relieve the pressure
ndash Decreasing pressureIncreasing volume favours more gas molecules
bull 1048766 The reaction shifts to restore the pressure
bull bull bull
Ta Da
Ta Da