Collision Theory

Factors affecting rate

Investigate how concentration affects rate

Collision Theory

1. For a reaction to occur the particles must collide

2. The colliding particles must have a minimum energy called the

Activation Energy

Collisions & Activation Energy

Next slide

Factors affecting Rate of reaction

1. Concentration

2. Temperature

3. Particle size

4. Nature of reactants

5. Presence of a catalyst

Effect of concentration on rate

Increasing concentration increases the rate

By increasing the number of collisions

The formation of a pale yellow precipitate of sulphur can be used to monitor the progress of

the reaction

HCl Na2S2O3 H2O+NaCl

Investigate the effect of concentration on reaction rate

+ + S+ SO2

To investigate the effect of concentration on reaction rate

Next slide

Add the HCl to the Na2S2O3 in the flask

Record the time taken for the X to disappear

Repeat with different concentrations of Na2S2O3 Inverse the time to get the rate

Effect of concentration on rate

RATE

CONCENTRATION

Conclusion ?

Rate is directly proportional to concentration

1

Time

Collision Theory

Factors affecting rate

Particle size affects rate

Collision Theory

1. For a reaction to occur the particles must collide

2. The colliding particles must have a minimum energy called the

Activation Energy

Factors affecting Rate of reaction

1. Concentration

2. Temperature

3. Particle size

4. Nature of reactants

5. Presence of a catalyst

Effect of Particle size on rate

Smaller particles have a greater surface area

Next slide

Surface area, collisions & rate

Next slide

The rate of release of CO2 gas can be used to monitor the progress of the reaction

HCl CaCO3 H2O +

Investigate the effect of particle size on reaction rate

+ + CO2CaCl2

Add the HCl to a large chips of CaCO3 in the flask

As CO2 is released the mass of the flask drops

Next slide

Record the time taken for the release of CO2 to end ( No further mass loss)

Repeat using the same mass of powdered CaCO3

and the same volume of HCl

And the same concentration of HCL

Result

Finely divided particles react faster than large particles

Collision Theory

Factors affecting rate

Investigate how temperature affects rate

Collision Theory

1. For a reaction to occur the particles must collide

2. The colliding particles must have a minimum energy called the

Activation Energy

Factors affecting Rate of reaction

1. Concentration

2. Temperature

3. Particle size

4. Nature of reactants

5. Presence of a catalyst

Temperature, Collisions & Activation Energy

Next slide

Effect of temperature on rate

Increasing temperature increases the rate

By increasing the number of collisions / sec

More of the colliding particles have E Act

The formation of a pale yellow precipitate of sulphur can be used to monitor the progress of

the reaction

HCl Na2S2O3 H2O+NaCl

Investigate the effect of temperature on reaction rate

+ + S+ SO2

To investigate the effect of temperature on reaction rate

Next slide

Add the HCl to the Na2S2O3 in the flask

Record the time taken for the X to disappear

Record the temperature after mixing

Inverse the time to get the rate

Next slide

Repeat at different temperatures

Effect of temperature on rate

RATE

TEMPERATURE

Conclusion ?

Rate increases with increasing temperature

1

Time

Effect of temperature on rate

RATE

TEMPERATURE

What is the main factor

increasing rate between A and B

Rate increases due to increased collisions /sec

1

Time

A

B

Effect of temperature on rate

RATE

TEMPERATURE

What other factor caused the large rate

increase between B and C

More colliding particles have E Act

1

Time

C

B

Nature of reactants affect the rate

Collision Theory

1. For a reaction to occur the particles must collide

2. The colliding particles must have a minimum energy called the

Activation Energy

Factors affecting Rate of reaction

1. Concentration

2. Temperature

3. Particle size

4. Nature of reactants

5. Presence of a catalyst

Nature of reactants affects rate

Ionic reactions are fast

Na+Cl- Ag+NO3-+ =

Ag+Cl-+

Na+NO3-

Mix solutions of sodium chloride and silver nitrate

A precipitate of silver chloride forms instantly

Ions are free to move in solution....no bonds to break

Sodium chloride + Silver Nitrate

next

The pale yellow precipitate of sulphur forms slowly as covalent bonds in the sodium thiosulfate must first

be broken before the reaction can occur

HCl Na2S2O3 H2O+NaCl+ + S+ SO2

Covalent reactions are slower than ionic

End