Chemical EquationA condensed shorthand statement which expresses a chemical reaction in terms of formulas and symbols. Indicates the reactants and the product/s of a chemical reaction A balanced equation gives a quantitative relationship of the reactants and the products.

Chemical Reactions

Combination Decomposition Displacement Replacement

Combinationsimplest conceivable reaction a reaction in which 2 or more substances unite to form a single compound ex. Fe + S FeS H2O + SO3 H2SO4 H2O + Na2O 2NaOH CaO + SiO2 CaSiO3

Decompositionreverse of combination reaction a reaction in which a substances yields two or more products. breaking up of binary compounds into its elements 2HgO 2Hg + O2 ex. 2KClO3 2 KCl + 3O2 CaCO3 CaO + CO2

Displacementa reaction in which compounds combine freeing one of its constituent element ex. Zn + 2HCl ZnCl2 + H2 Fe + CuSO4 FeSO4 + Cu Cl2 + NaBr 2NaCl + Br2 CaCO3 + SiO2 CaSiO3 + CO2

Replacementa reaction in which there is an interchange of elements (or radicals) between two compound ex. AgF + NaCl AgCl + NaF AgNO3 + NH4Cl AgCl + NH4NO3 3Ca(NO3)2 + 2Na3PO4 Ca3(PO4)2 + 6NaNO3 BaCl2 + NaSO4 BaSO4 + 2NaCl

Other Types of Reactions Combustion Neutralization Endothermic/ Exothermic Oxidation/ Reduction Precipitation

Combustion Combustion is a vigorous and exothermic reaction that takes place between certain substances (particularly organic compounds) with oxygen

Valenceproperty of an element combining capacities of many elements associated with the number of electrons in the outermost principal quantum level of an atom

Radicals Groups of atoms that remains intact throughout many chemical reactions and which exhibit constant valence in all compounds in which it is present.

Stoichiometry Greek for measuring elements The calculations of quantities in chemical reactions based on a balanced equation. We can interpret balanced

In terms of Particles Element - atoms Molecular compound (non-metals) - molecule Ionic Compounds (metal and non-metal) - formula unit

2H2 + O2 2H2OTwo molecules of hydrogen and one molecule of oxygen form two molecules of water. 2 Al2O3 4Al + 3O22 formula unitsAl2O3 form 4atoms Al and 3 molecules O2 2Na + 2H2O 2NaOH + H2

Look at it differently2H2 + O2 2H2O2 dozen molecules of hydrogen and 1 dozen molecules of oxygen form 2 dozen molecules of water. 2 x (6.02 x 1023) molecules of hydrogen and 1 x (6.02 x 1023) molecules of oxygen form 2 x (6.02 x 1023) molecules of water. 2 moles of hydrogen and 1 mole of

In terms of Moles2 Al2O3 4Al + 3O2 2Na + 2H2O 2NaOH + H2 The coefficients tell us how many moles of each kind

In terms of massThe law of conservation of mass applies We can check using moles

2H2 + O2 2H2O= 4.04 g H2 2 moles H2 1 moles H2 = 32.00 g O2 1 moles O2 1 moles O2 36.04 36.04 g H2 + O2 H2O 32.00 g O2 2.02 g H2

In terms of mass2H2 + O2 2H2O18.02 g H2O = 36.04 g H2O 2 moles H2O 1 mole H2O

2H2 + O2 2H2O36.04 g (2H2 + O2) = 36.04 g H2O

Your turn Show that the following equation follows the Law of conservation of mass. 2 Al2O3 4Al + 3O2

Mole to Mole conversionsHow many moles of O2 are produced when 3.34 moles of Al2O3 decompose? 2 Al2O3 4Al + 3O23.34 moles Al2O3 3 mole O2 2 moles Al2O3

= 5.01 moles O2

Your turn2C2H2 + 5 O2 4CO2 + 2 H2O If 3.84 moles of C2H2 are burned, how many moles of O2 are needed? If 2.47 moles of C2H2 are burned, how many moles of CO2 are formed? How many moles of C2H2 are needed to produce 8.95 mole of H O?

Mass in Chemical Reactions

For example... If 10.1 g of Fe are added to a solution of Copper (II) Sulfate, how much solid copper would form? Fe + CuSO4 Fe2(SO4)3 + Cu 2Fe + 3CuSO4 Fe2(SO4)3 + 3Cu 10.1 g Fe 1 mol Fe 55.85 g Fe = 0.181 mol Fe

2Fe + 3CuSO4 Fe2(SO4)3 + 3Cu

3 mol Cu 0.181 mol Fe = 0.2715 mol Cu 2 mol Fe 63.55 g Cu 0.2715 mol Cu = 17.25 g Cu 1 mol Cu

Another way of doing it ...10.1 g Fe 1 mol Fe 3 mol Cu 63.55 g Cu 55.85 g Fe 2 mol Fe 1 mol Cu = 17.24 g Cu

ExamplesTo make silicon for computer chips they use this reaction SiCl4 + 2Mg 2MgCl2 + Si How many grams of Mg are needed to make 9.3 g of Si? How many grams of SiCl4 are needed to make 9.3 g of Si? How many grams of MgCl2 are produced along with 9.3 g of

More ExamplesThe U. S. Space Shuttle boosters use this reaction 3Al(s) + 3NH4ClO4 Al2O3 + AlCl3 + 3NO + 6H2O How much Al must be used to react with 652 g of NH4ClO4 ? How much water is produced? How much AlCl3 is produced?

And still another example If 6.45 moles of water are decomposed, how many liters of oxygen gas will be produced at STP?

To compute it... If 6.45 grams of water are decomposed, how many liters of oxygen will be produced at STP? 2H2O 2H2 + O2 6.45 g H2O 1 mol H2O 4.01 L O2 1 mol O2 22.42 L O2 18.02 g H2O 2 mol H2O 1 mol O2

Your TurnHow many liters of CO2 at STP will be produced from the complete combustion of 23.2 g C4H10 ? What volume of oxygen will be required?

Did you get it2C4H10 + 13O2 8CO2 + 10H2O23.2 g C4H10 1 mol C4H10 58.1 g C4H10 22.42 L CO2 1 mol CO2 35.81 L CO2 8 mol CO2 2 mol C4H10

Did they got it2C4H10 + 13O2 8CO2 + 10H2O23.2 g C4O10 1 mol C4H10 58.1 g C4H10 22.42 L O2 1 mol O2 58.19 L O2 13 mol O2 2 mol C4H10

Gases and Reactions

QuizHow many liters of CH4 at STP are required to completely react with 17.5 L of O2 ? CH4 + 2O2 CO2 + 2H2O1 mol O2 1 mol CH4 22.4 L CH4 17.5 L O2 22.4 L O2 2 mol O2 1 mol CH4 = 8.75 L CH4

Avogadro told us Equal volumes of gas, at the same temperature and pressure contain the same number of particles. Moles are numbers of particles You can treat reactions as if they happen liters at a time,

ExampleHow many liters of CO2 at STP are produced by completely burning 17.5 L of CH4 ? CH4 + 2O2 CO2 + 2H2O17.5 L CH4 1 L CO2 1 L CH4 = 17.5 L CO2

Limiting ReagentIf you are given one dozen loaves of bread, a gallon of mustard and three pieces of salami, how many salami sandwiches can you make. The limiting reagent is the reactant you run out of first. The excess reagent is the one you have left over. The limiting reagent determines how

How do you find out?Do two stoichiometry problems. The one that makes the least product is the limiting reagent. For example Copper reacts with sulfur to form copper ( I ) sulfide. If 10.6 g of copper reacts with 3.83 g S how much product will be formed?

If 10.6 g of copper reacts with 3.83 g S. How many grams of product will be formed? Cu is 2Cu + S Cu2S Limiting 1 mol Cu 1 mol Cu2S 159.16 g Cu2S Reagent 10.6 g Cu 63.55g Cu 2 mol Cu 1 mol Cu2S = 13.3 g Cu2S3.83 g S

1 mol S32.06g S

1 mol Cu2S 159.16 g Cu2S 1 mol S 1 mol Cu2S

= 19.0 g Cu2S

Your turnIf 10.1 g of magnesium and 2.87 L of HCl gas are reacted at STP, how many liters of gas will be produced?.128

Identify the limiting reagent.How many grams of solid is produced?6.1

How much excess reagent remains?8.544

Your Turn Again If 10.3 g of aluminum are reacted with 51.7 g of CuSO4 how much copper will be produced? How much excess reagent will remain?

YieldThe amount of product made in a chemical reaction. There are three types Actual yield- what you get in the lab when the chemicals are mixed Theoretical yield- what the balanced equation tells you you should make. Percent yield = Actual x 100 % Theoretical

Example6.78 g of copper is produced when 3.92 g of Al are reacted with excess copper (II) sulfate. 2Al + 3 CuSO4 Al2(SO4)3 + 3Cu What is the actual yield? What is the theoretical yield? What is the percent yield?49

13.85

Chemical ThermodynamicsEnergy in Chemical Reactions How Much?In or Out?

EnergyEnergy is measured in Joules or calories Every reaction has an energy change associated with it Exothermic reactions release energy, usually in the form of heat. Endothermic reactions absorb energy

C + O2 CO2 395 kJ +Energy C + O2 395kJ C + O2 Reactants Products

In terms of bondsC O O C O O

Breaking this bond will require energy O C O C O O Making these bonds gives you energy In this case making the bonds gives you more energy than breaking them

Exothermic The products are lower in energy than the reactants Releases energy

CaCO176 kJ CaO + CaCO3 + 3 CaO + CO2 CO2Energy CaO + CO2 176 kJ CaCO3 Reactants Products

Endothermic The products are higher in energy than the reactants Absorbs energy

Chemistry Happens inMOLES An equation that includes energy is called a thermochemical equation CH4 + 2 O2 CO2 + 2 H2O + 802.2 kJ 1 mole of CH4 makes 802.2 kJ of energy. When you make 802.2 kJ you

CH4 + 2 O2 CO2 + 2 H2O + 802.2 kJ

If 10. 3 grams of CH4 are burned completely, how much heat will be produced?10. 3 g CH4 1 mol CH4 16.05 g CH4 =514 kJ 802.2 kJ 1 mol CH4

CH4 + 2 O2 CO2 + 2 H2O + 802.2 kJ

How many liters of O2 at STP would be required to produce 23 kJ of heat? How many grams of water would be produced with 506 kJ of heat?

EnthalpyThe heat content a substance has at a given temperature and pressure Cant be measured directly because there is no set starting point The reactants start with a heat content The products end up with a heat content So we can measure how much

EnthalpySymbol is H Change in enthalpy is H delta H If heat is released the heat content of the products is lower H is negative (exothermic) If heat is absorbed the heat content of the products is higher H is positive (endothermic)

Energy

Change is down H is 0

Reactants

Products

Heat of ReactionThe heat that is released or absorbed in a chemical reaction Equivalent to H C + O2(g) CO2(g) +393.5 kJ C + O2(g) CO2(g) H = -393.5 kJ In thermochemical equation it is important to say what state H2(g) + 1/2O2 (g) H2O(g) H = -241.8 kJ H2(g) + 1/2O2 (g) H2O(l) H = -285.8 kJ

Heat of CombustionThe heat from the reaction that completely burns 1 mole of a substance C2H4 + 3 O2 2 CO2 + 2 H2O C2H6 + O2 CO2 + H2O 2 C2H6 + 5 O2 2 CO2 + 6 H2O C2H6 + (5/2) O2 CO2 + 3 H2O

Standard Heat of FormationThe H for a reaction that produces 1 mol of a compound from its elements at standard conditions 0 Standard conditions: 25C and 1 H f atm. xThe standard heat of formation of an Symbol is element is 0xThis

includes the diatomics

What good are they?There are tables of heats of formations The heat of a reaction can be calculated by subtracting the heats of formation of the reactants from the products H = H 0 (products ) - H 0 (reactants) f f

Examples CH4(g) + 2 O2(g) CO2(g) + 2 H2O(g)

H2O(g) = -241.8 kJ x H= [-393.5 + 2(-241.8)]-[-74.68 +2 (0)] x H= 802.4 kJ

0 H f 0 H f 0 H f 0 H f

CH4 (g) = -74.86 kJ O2(g) = 0 kJ CO2(g) = -393.5 kJ

Why Does It Work? If H2(g) + 1/2 O2(g) H2O(g) H=-285.5 kJ then: H2O(g) H2(g) + 1/2 O2(g) H =+285.5 kJ If you turn an equation around, you change the sign 2 H2O(g) 2 H2(g) + O2(g) H =+571.0 kJ If you multiply the equation by a number, you multiply the heat by that number.

Why does it work?You make the products, so you need their heats of formation You unmake the products so you have to subtract their heats.

Practice ProblemDiborane, B2H6 is a highly reactive boron hydride. Calculate the H for the synthesis of diborane from its elements according to the equation 2 B (s) + 3 H2 (g) B2H6 (g) and the following data: 2B(s) + 3/2O2(g) B2O3 -1273 kJ B2H6(g) + 3O2(g) B2O3(s) + 3H2O(g) -2035 kJ

2B

(s)

+ 3 H2 (g) B2H6 (g)

2B(s) + 3/2O2(g) B2O3 -1273 kJ B2H6(g) + 3O2(g) B2O3(s) + 3H2O(g) -2035 kJ H2(g) + 1/2O2(g) H2O(l) -286 kJ

Hesss LawIn going from a particular set of reactants to a particular set of products, the enthalpy change is the same whether the reaction takes place in one step or in a series of steps

QuizFind the enthalpy change for the chemical reaction given below: 2 SO3(g) 2 SO2(g) + O2(g)0 f H

SO2 (g) SO3 (g)

-297 kJ/mol -396 kJ/mol

0 H f

SO2 (g) SO3 (g)

-297 kJ/mol -396 kJ/mol

2(-297) - [ 2(-396)] = 198

198 kJ/mol

1st Law of Thermodynamics

Energy can neither be created nor destroyed the capacity to do work or cause heat flow

Types of EnergyPotential Energy - energy due to position or composition Kinetic Energy - energy due to motion and depends on mass and velocity of the

nd Law of Thermodynamics

In any spontaneous process there is always an increase in the entropy of the universe the entropy of the universe isincreasing

EntropyA thermodynamic function Symbol is S It is a measure of randomness or disorder A driving force for spontaneous process

Entropy (S)Change in entropy is S (delta S) If the reaction is accompanied by production of heat S is positive If the reaction involves heat absorption S is negative If the reaction neither

Change in Entropy (S) S > 0 spontaneous reaction S < 0 not spontaneous reaction S = 0 system at equilibrium

Factors Affecting S

Heat flow Temperature

Suniv = Ssys + SsurrConsider liquid water, H2O H2 O(l) (l)

H2 O

(g)

44 kJ

Ssys Ssurr suniv+ + + + + + + Ssys>Ssurr SsysSsurr Ssys 333 K or T > 60

H2O (s) H2O (l) At what temperature is the process spontaneous at 1 atm?H = 6033 J/mol S = 22.1 G = H - TS = 0 J/Kmol T = H/S = 273 Ans. = > 0 C

H2O (l) H2O (g) At what temperature is the process spontaneous at 1 atm?H = 44.4 kJ/mol S = 119 G = H - TS = 0 J/Kmol T = H/S = 373 Ans. = > 100 C

Chemical Kinetics

Chemical ReactionCan be classified into several types like neutralization, precipitation, redox, etc. Affected by several factors like nature of reactants, pressure, temperature, etc. It is defined or represented by its reactants and products

Chemical Kinetics The area of chemistry that is involved in rates of chemical reactions

Reaction Rates?defined as the change in concentration of reactant or product per unit time

[] Rate = t

2 NO2 (g) 2 NOTime (1 s) 0 50 100 150

(g)

+ O2 (g)

Concentration (mol/L)

NO20.0100 0.0079 0.0065 0.0055

NO0.0000 0.0021 0.0035 0.0045

O20.0000 0.0011 0.0018 0.0023

Calculate the average rate at which the concentration of NO2 changes over the first 50 [2] seconds. []Rate = = t = t [2]t = 50 s - [2]t = 0 s50 s - 0 s

= - 4.2 x 10-5 M/s

Collision model A model based on the idea that atoms/molecules must collide to react The model used to account for the observed behavior and characteristics of reaction rates.

EnergyThe threshold energy that must be overcome to produce a chemical reaction

2 BrNO (g) 2 NO

(g)

+ Br2 (g)

2 Br-N bonds must be broken 1 Br-Br bond must be formed the kinetic energy possessed by the reacting molecules, BrNO + BrNO is required to break the bond

Potential Energy

ON---Br ON---Br

bond breaking bond forming

Ea2 BrNO 2NO + Br2

}E

Reaction Progress

Complex or Transition State

The arrangement of atoms found at the top of the potential energy barrier as reaction proceeds to completion