1. What is stoichiometry? A problem solving method used to calculate the amount of product made or amount of reactant needed in a chemical reaction What is a mole? A mole is the measurement for the amount of a substance. 1 mole = molar mass (g) of substance What is the mole ratio? Ratio of moles of one substance to moles of another substance. Use the coefficients from balanced equation. 2H 2 + O 2  2H 2 O Ratio of H 2 to O 2 ? 2:1 Ratio of H 2 to H 2 O? 2:2 Ratio of O 2 to H 2 O? 1:2 Review: Calculate molar mass of Cu(NO 3 ) 2 Cu = 1 x 63.55 = 63.55 N = 2 x 14.01 = 28.02 O = 6 x 16.00 = 96.00 187.57 g/mol Remember: round all masses to 2 places past decimal Conservation of Mass -What is conserved in a chemical reaction? - total mass - # of atoms of each element -What is NOT conserved in a chemical reaction? - # of moles - # of molecules

2. One disadvantage of burning propane (C 3 H 8 ) is that carbon dioxide is one of the products. The released carbon dioxide increases the growing amount in the atmosphere. How many moles of carbon dioxide are produced when 10.0 moles of propane are burned in excess oxygen in a gas grill? C 3 H 8 + 5O 2  3CO 2 + 4H 2 O 10 mol ? mol 10 mol C 3 H 8 3 mol CO 2 = 30 mol CO 2 1 mol C 3 H 8 How many moles of ammonia (NH 3 ) are produced when 0.60 moles of nitrogen react with hydrogen? N 2 + 3H 2  2NH 3 0.60 mol ? mol 0.60 mol N 2 2 mol NH 3 = 1.2 mol NH 3 1 mol N 2 Zinc reacts with iodine in a synthesis reaction. Determine the theoretical yield if a 125.0 g sample of zinc was used. Determine the percent yield if 515.6 g product is recovered. Zn + I 2  Zn I 2 125.0 g ? g 125.0 g Zn 1 mol Zn 1 mol Zn I 2 319.19 g Zn I 2 = 610.2 g Zn I 2 65.39 g Zn 1 mol Zn 1 mol Zn I 2 Actual_____ x 100515.6 g Zn I 2 x 100 = 84.50 % Theoretical610.2 g Zn I 2

3. A solution of potassium chromate reacts with a solution of lead (II) nitrate. Starting with 0.250 moles of potassium chromate, determine the mass of the lead (II) chromate produced. K 2 CrO 4 + Pb(NO 3 ) 2  PbCrO 4 + 2KNO 3 0.250 mol ? g 0.250 mol K 2 CrO 4 1 mol PbCrO 4 323.19 g PbCrO 4 = 80.8 g PbCrO 4 1 mol K 2 CrO 4 1 mol PbCrO 4 What is the theoretical yield of sodium chloride (i.e. calculate the grams) produced when 1.25 moles of chlorine gas reacts vigorously with sodium. 2Na + Cl 2  2NaCl 1.25 mol ? g 1.25 mol Cl 2 2 mol NaCl 58.44 g NaCl = 146 g NaCl 1 mol Cl 2 1 mol NaCl Aluminum chloride is an inexpensive reagent used in many industrial processes. It is made by treating scrap aluminum with chlorine. If you start with 2.70 g of aluminum and 4.05 g of chlorine, which reactant is limiting? How many grams of aluminum chloride are produced? 2Al + 3Cl 2  2AlCl 3 2.70 g 4.05 g ? g 2.70 g Al 1 mol Al 2 mol AlCl 3 133.34 g AlCl 3 = 13.3 g AlCl 3 26.98 g Al 2 mol Al 1 mol AlCl 3 LR = Cl 2 because it makes less AlCl 3 4.05 g Cl 2 1 mol Cl 2 2 mol AlCl 3 133.34 g AlCl 3 = 5.08 g AlCl 3 70.9 g Cl 2 3 mol Cl 2 1 mol AlCl 3

4. One in a series of reactions that inflate air bags in automobiles is the decomposition of sodium azide (NaN 3 ). Determine the number of moles of N 2 produced if 100.0 g of NaN 3 is decomposed. 2NaN 3  3N 2 + 2Na 100.0 g ? mol 100.0 g NaN 3 1 mol NaN 3 3 mol N 2 = 2.307 mol N 2 65.01 g NaN 3 2 mol NaN 3 Solid silicon dioxide, often called silica, reacts with hydrofluoric acid solution to produce the gas silicon tetrafluoride and water. How many moles of acid are needed to produce 60.0 grams of silicon tetrafluoride? SiO 2 + 4HF  SiF 4 + 2H 2 O ? mol 60.0 g 60.0 g SiF 4 1 mol SiF 4 4 mol HF = 2.31 mol HF 104.08 g SiF 4 1 mol SiF 4 Ammonium nitrate, an important fertilizer, produces dinitrogen monoxide gas and water when it decomposes. Calculate the grams of water produced from the decomposition of 25.0 g of solid ammonium nitrate. NH 4 NO 3  N 2 O + 2H 2 O 25.0 g ? g 25.0 g NH 4 NO 3 1 mol NH 4 NO 3 2 mol H 2 O 18.02 g H 2 O = 11.3 g H 2 O 80.04 g NH 4 NO 3 1 mol NH 4 NO 3 1 mol H 2 O Determine the mass of CO 2 produced from the combustion of 100.0 g ethanol (C 2 H 5 OH). C 2 H 5 OH + 3O 2  2CO 2 + 3H 2 O 100.0 g? g 100.0 g C 2 H 5 OH 1 mol C 2 H 5 OH 2 mol CO 2 44.01 g CO 2 = 191.1 g CO 2 46.07 g C 2 H 5 OH 1 mol C 2 H 5 OH 1 mol CO 2