Chapter 9: STOICHIOMETRY 9.1 Information Given by Chemical Equations AIM: To understand the _________________ and __________ information given in a balanced equation Write the equation… 1 molecule of propane (C3H8) reacts with 5 molecules of Oxygen to give 3 molecules of carbon dioxide and 4 molecules of water Can we say 1 mole of C3H8 molecules reacts with…? Can we also say that 1 gram of propane reacts with…? 9.2 Mole-Mole Relationships AIM: To learn to use a balanced equation to determine relationships between moles of _______________and moles of _______________ Stoichiometry is the relationship between… Reactants and other _______________ Reactants and _______________ Products and other _______________ Molar ratio _______________from chemical equation Write the equation... Water decomposes to produce hydrogen and oxygen How many moles of oxygen will be produced by the decomposition of 5.8 mol of water? Given the following equation... C3H8 + 5 O2 --> 3 CO2 + 4 H2O Calculate the number of moles of oxygen required to react exactly with 4.30 mol of propane. Calculate the number of moles of carbon dioxide formed when 4.30 mol of propane react with 21.5 mol of oxygen Homework 9.1 Information Given by Chemical Equations 1. What do the coefficients of a balanced chemical equation tell us about the proportions in which atoms and molecules react on an individual (microscopic) basis? 3. Although mass is a property of matter we can conveniently measure in the laboratory, the coefficients of a balanced chemical equation are not directly interpreted on the basis of mass. Explain why. 7. True or false? For the reaction represented by the chemical equation 2 H2O2 (aq) → 2H2O (l) + O2 (g) if 2.0 g of hydrogen peroxide decomposes, then 2.0 g of water and 1.0 g of oxygen gas will be produced. Homework 9.2 Mole-Mole Relationships 13. For each of the following balanced reactions, calculate how many moles of each product would be produced by complete conversion of 1.25 mol of the reactant indicated in boldface. State clearly the mole ratio used for the conversion. a. C2H5OH(l) + 3O2 (g) → 2CO2 (g) + 3 H2O (g) b. N2(g) + O2 (g) → 2NO (g) c. 2NaClO2(s) + Cl2 (g) → 2ClO2 d. 3 H2(g) + N2 (g) → 2NH3 (g) + 2 NaCl (s) (g) 15. For each of the following equations, indicate how many moles of the second reactant would be required to react exactly with 0.275 mol of the first reactant. State clearly the mole ratio used for the conversion. a. Cl2(g) + KI(aq) → I2 (s) + KCl (aq) b. Co(s) + P4 (s) → Co3P2 c. Zn(s) + HNO3 (aq) → ZnNO3 d. C5H12(l) + O2 (g) → CO2 (s) + H2 (g) (aq) + H2O (g) (g) Warm-Up Calculate the moles of water formed from 22.0 mol of propane C3H8 + 5 O2 --> 3 CO2 + 4 H2O 9.3 Mass Calculations AIM: To learn to relate ________________of reactants and products in a chemical reaction 2 Al + 3 I2 --> 2 AlI3 Suppose we have 35.0 g of Al. What mass of iodine should be weighed out to react exactly with this amount? C3H8 + 5 O2 --> 3 CO2 + 4 H2O What mass of oxygen will be required to react exactly with 96.1 g of propane? 9.4 Calculations Involving a Limiting Reactant AIM: To learn to recognize the _____________________ in a reaction To learn to use the limiting reactant to do _____________________ calculations How many S’mores can you make if you start with… 2 graham cracker halves, 6 chocolate squares, 1 marshmallow 6 graham cracker halves, 18 chocolate squares, 3 marshmallow 20 graham cracker halves, 60 chocolate squares, 1 marshmallow Limiting Reactant Limiting reactant : N2 + 3 H2 --> 2 NH3 Suppose 25.0 kg of nitrogen gas and 5.00 kg of hydrogen gas are mixed and reacted to form ammonia. Calculate the mass of ammonia produced when this reaction is run to completion Homework 9.3 Mass Calculations 25. For each of the following equations, calculate how many grams of each product would be produced by complete reaction of 12.5 grams of the reactant indicated in boldface. Indicate clearly the mole ratio used for the conversation. a. TiBr4(g) + H2(g) → Ti (s) + HBr (g) b. SiH4(g) + NH3 (g) → Si3N4 c. NO(g) + H2 (g) → N2 + H2 (g) (s) + H2O (l) (g) d. Cu2S(s) → Cu (s) + S (g) Homework 9.4 Calculations Involving a Limiting Reactant 47. For each of the following chemical equations, suppose 10.0g of each reactant is taken. Show by calculation which reactant is the limiting reagent. Calculate the mass of each product that is expected. a. C3H8(g) + O2 (g) → CO2 (g) + H2O (g) b. Al(s) + Cl2 (g) → AlCl3 (s) c. NaOH(s) + CO2 (g) → Na2CO3 + H2O (l) d. NaHCO3(s) +HCl (aq) → NaCl (aq) + H2O (l) + CO2 (s) (g) Warm-Up Write the complete balanced equation that represents the following statement… When bare copper wire is placed in a solution of silver nitrate, a replacement reaction occurs in which silver metal and copper(II)nitrate solution are produced 1. If 1.5 grams of silver nitrate reacts with a 1.0 gram copper wire, how much silver will be produced? 9.5 Percent Yield AIM: To learn to calculate _______________ as a percentage of __________________ Percent Yield Percent yield = ________________ Actual Yield: Theoretical Yield: 2 H2 + CO --> CH3OH Calculate the theoretical yield of methanol when 68.5 kg of CO is reacted with 8.60 kg of H2 If 3.37 x 104 g are actually produced, what is the percent yield? Homework 9.5 Percent Yield 61. According to his prelaboratory theoretical yield calculations, a student’s experiment should have produced 1.44 g of magnesium oxide. When he weighed his product after reaction, only 1.23 g of magnesium oxide was present. What is the student’s percent yield? 65. What is the theoretical mass of xenon tetrafluoride that should form when 130. g of xenon is reacted with 100. g of F2? What is the percent yield if only 145 g of XeF4 is actually isolated? Xe(g) + 2F2(g) → XeF4(s) Mixed Review 69. Suppose 5.25 g of iron filings is combined with 12.7 g of sulfur. What is the theoretical yield of iron(II) sulfide? Fe(s) + S(s) → FeS(s) 70. When the sugar glucose C6H12O6, is burned in air, carbon dioxide and water vapor are produced. Write the balanced chemical equation for this process. And calculate the theoretical yield of carbon dioxide when 1.00 g of glucose is burned completely. 71. What is the theoretical yield of Cu2S when 31.8 g of Cu(s) is heated with 50.0 g of S? Assume only Cu2S is produced in the reaction. What is the percent yield of Cu2S if 40.0 g of Cu2S can be isolated from the mixture. 2 Cu(s) + S(s) → Cu2S(s) 79. Using the average atomic masses from the periodic table, calculate how many moles of each substance the following masses represent. a. 4.65 g of C2H5OH b. 7.94 g of barium nitrate 89. For each of the following unbalanced chemical equations, suppose 25.0 g of each reactant is used. Show by calculation which reactant is limiting. Calculate the theoretical yield in grams of the product in boldface. a. C2H5OH(l) + O2 (g) → CO2(g) + H2O(l) b. N2(g) + O2 (g) → NO(g) 91. For each of the following unbalanced chemical equations, suppose 25.0 mol of each reactant is used. Show by calculation which reactant is limiting. Calculate the theoretical yield in grams of the product in boldface. a. NaClO2(aq) + Cl2 (g) → ClO2(g) + NaCl(aq) b. H2(g) + N2 (g) → NH3(g)