1. Stoichiometry Chapter 12 Chemistry 2

2. The Arithmetic of Equations 12.1

3. Using Everyday Equations 12.1 Cookie recipe like chemical equations Cookie recipe like chemical equations Ingredients = reactants Ingredients = reactants Cookies = products Cookies = products Using Balanced Chemical Equations Using Balanced Chemical Equations Stoichiometrythe calculation of quantities in chemical reactions Stoichiometrythe calculation of quantities in chemical reactions Form of book keeping Form of book keeping

6. Interpreting Chemical Equations 12.1 Balanced chemical equations = gives amount of reactants and products Balanced chemical equations = gives amount of reactants and products Can be interpreted in different quantities Can be interpreted in different quantities # of Atom  same # on both sides of reaction # of Atom  same # on both sides of reaction Mass  if # of atoms doesn’t change, mass doesn’t chane Mass  if # of atoms doesn’t change, mass doesn’t chane Law of conservation of mass Law of conservation of mass Same on both sides Same on both sides Moles  indicated by coefficients Moles  indicated by coefficients Not same on both sides of equation Not same on both sides of equation # of Molecules # of Molecules Volume  @ STP 1 mole= 22.4 L Volume  @ STP 1 mole= 22.4 L

7. Mass Conservation in Chemical Reactions 12.1 Mass and atoms are conserved in EVERY chemical reaction Mass and atoms are conserved in EVERY chemical reaction Molecules, formula units, moles, and volume not same on both sides of equation Molecules, formula units, moles, and volume not same on both sides of equation

10. Chemical Calculations 12.2

11. Writing and Using Mole Ratios 12.2 Mole ratio – conversion factor derived from the coefficients of a balanced chemical equation interpreted in terms of moles Mole ratio – conversion factor derived from the coefficients of a balanced chemical equation interpreted in terms of moles N 2 + 3H 2  2NH 3 N 2 + 3H 2  2NH 3 1 mole N 2 /3 mole H 2 1 mole N 2 /3 mole H 2 2 mole NH 3 /1mole N 2 2 mole NH 3 /1mole N 2

12. Mole-Mole Calculations

14. Mass-Mole Calculations 12.2 No lab balance can determine # of moles  must find mass in grams and convert to moles No lab balance can determine # of moles  must find mass in grams and convert to moles

16. Steps in Solving a Mass-Mass Problem 12.2 Given quantity  wanted quantity Given quantity  wanted quantity aG  bW aG  bW 1. Change mass of G to moles of G 1. Mass G x 1 mol G/molar mass of G = mol G 2. Change moles of G to moles of W 1. mol G x b mol W/a mol G = mol W 3. Change mol W to mass of W 1. mol W x molar mass of W/1 mol W = mass W

18. Other Stoichiometric Calculations 12.2 REVIEW… REVIEW… Relate to moles… we always have a conversion for moles Relate to moles… we always have a conversion for moles Can’t go from one unit to another without passing thru moles! Can’t go from one unit to another without passing thru moles! 1 mol/molar mass & molar mass/1 mol 1 mol/molar mass & molar mass/1 mol 1 mol/6.02x10 23 particles & 6.02x10 23 particles/1 mol 1 mol/6.02x10 23 particles & 6.02x10 23 particles/1 mol 1 mol/22.4 L & 22.4 L/1 mol 1 mol/22.4 L & 22.4 L/1 mol Coefficients represent # of moles & relative volumes of interacting gases Coefficients represent # of moles & relative volumes of interacting gases Use volume ratios same way you would used mole ratios Use volume ratios same way you would used mole ratios

25. Limiting Reagent and Percent Yield 12.3

26. Limiting and Excess Reagents 12.3 Insufficient quantity of reactants will limit amount of product formed Insufficient quantity of reactants will limit amount of product formed Balanced chemical equation = chemist’s recipe Balanced chemical equation = chemist’s recipe

27. Limiting and Excess Reagents 12.3 Limiting reagent – reagent that determines th eamount of product formed Limiting reagent – reagent that determines th eamount of product formed Completely used up Completely used up H in previous equation H in previous equation Excess Reagent – reactant that is not completely used up Excess Reagent – reactant that is not completely used up N in previous equation N in previous equation If have a word problem that gives you anything other than moles and asks to solve to limiting reagent, turn to moles first! If have a word problem that gives you anything other than moles and asks to solve to limiting reagent, turn to moles first!

32. Percent Yield 12.3 Percentage = ratio of 2 items Percentage = ratio of 2 items Test = # of answers correct/total # of questions x 100 Test = # of answers correct/total # of questions x 100 How well you preformed to how well you could have preformed! How well you preformed to how well you could have preformed! Percent yield = ratio of actual yield to theoretical yield Percent yield = ratio of actual yield to theoretical yield Actual yield = amount of product actually formed Actual yield = amount of product actually formed Theoretical yield = maximum amount of product that could be formed Theoretical yield = maximum amount of product that could be formed Percent yield = actual yield/theoretical yield x 100% Percent yield = actual yield/theoretical yield x 100% Measure of the efficiency of reaction in lab Measure of the efficiency of reaction in lab Normally not larger than 100% Normally not larger than 100% Many factors for less than 100% Many factors for less than 100% Reaction not to completion Reaction not to completion Impure reactants Impure reactants Loss of product during filtration or transfer between containers Loss of product during filtration or transfer between containers

33. Just the RIGHT Volume of Gas Engineers use Stoichiometry to determine the exact quantity of each reactant in the air bag’s inflation system Engineers use Stoichiometry to determine the exact quantity of each reactant in the air bag’s inflation system How airbags work How airbags work Collision triggers crash sensor  sends signal to an igniter Collision triggers crash sensor  sends signal to an igniter Igniter triggers chemical reactions that releases N gas, filling the bag in.05 seconds Igniter triggers chemical reactions that releases N gas, filling the bag in.05 seconds Small holes in bag release N gas = deflation Small holes in bag release N gas = deflation Car Facts Car Facts 17.1 million vehicles sold in 2002 in US 17.1 million vehicles sold in 2002 in US Cadillac Escalade SUV most frequent theft claims in passenger vehicles Cadillac Escalade SUV most frequent theft claims in passenger vehicles At night, headlight illuminate 160ft in front of your car. If your driving 40 mph you reaction distance is 88 ft and braking distance is 101 ft= stopping distance of 189 ft!! At night, headlight illuminate 160ft in front of your car. If your driving 40 mph you reaction distance is 88 ft and braking distance is 101 ft= stopping distance of 189 ft!!