VOCABULARY Define. 1. stoichiometry. 2. composition stoichiometry. 3. reaction stoichiometry. 4. unknown. 5. mole ratio

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1 CHAPTER 9 HOMEWORK 9-1 (pp ) Define. 1. stoichiometry 2. composition stoichiometry 3. reaction stoichiometry 4. unknown 5. mole ratio SKILL BUILDER On a separate sheet of paper, write five possible mole ratios for each of the chemical reactions. a. C 3 H 8 O 3 + 3HCl C 3 H 5 Cl 3 + 3H 2 O b. 2Fe 2 O 3 + 3C 4Fe + 3CO 2 c. SiO 2 + 4HF SiF 4 + 2H 2 O 1. Which statement is true? a. Mole ratios limit the number of significant figures in a calculation. b. You must know the masses of all the reactants in a chemical equation in order to determine the masses of all the products. c. The mole ratio is needed only to solve problems in which the given is a mass in grams and the unknown is an amount in moles. d. A mole ratio can only be determined from a correctly balanced chemical equation. 2. Antoine Laurent Lavoisier s contribution to chemistry was a. the law of conservation of mass. b. the law of conservation of energy. c. the periodic table of elements. d. the phlogiston theory of combustion.

2 CHAPTER 9 HOMEWORK 9-2 (pp ) Complete each sentence. 1. The mole ratio is obtained from. 2. Theoretical stoichiometric calculations show. 3. The conversion factor needed to calculate the amount of moles of one substance that will react with or be produced from the given amount in moles of another substance is 4. To solve the problem described in item 3, one needs to 5. To calculate the mass (in grams) of a substance that will react with or be produced from a given amount in moles of a second substance, the two pieces of information required are SKILL BUILDER Solve the problems on a separate sheet of paper. 1. Given the general chemical equation A 3C + D, a. How many moles of C can be produced from one mole of A? b. How many moles of D can produced from four moles of A? 2. Given the general chemical equation 3A + 2B C + 5D, a. How many moles of D can be produced from 4 moles of A? b. How many liters of D can be prepared from 9.8 L of B? 3. Sodium reacts with water to produce sodium hydroxide and hydrogen gas: 2Na + 2H 2 O 2NaOH + H 2. a. How many moles of water are required to react with 14 moles of sodium? b. How many moles of NaOH will result if 15 moles of sodium are used? 1. For the general chemical equation 2A + 3B 4C + D, how many moles of A are required to produce 18.4 mol of C? a. 9.2 mol b mol c mol d mol 2. For the chemical reaction represented by the equation C 8 H 8 + 5O 2 3CO 2 + 4H 2 O, how many moles of O 2 are required to react with 16.4 moles of C 8 H 8? a mol b mol c mol d. 82 mol

3 CHAPTER 9 HOMEWORK 9-3 (pp ) AND SKILL BUILDER Complete the chart. Type of Calculation the amount in moles of one substance that will react with or be produced from the given amount in moles of another substance Additional Information Required the amount in moles of one substance that will react with or be produced from a given mass of another substance the mass of a substance that will react with or be produced from a given amount in moles of a second substance GRAPHIC ORGANIZER Create a flow chart or other type of diagram to show the various conversion factors needed to solve different types of stoichiometric calculations. Consider what is given, unknown, and the information needed to solve for each unknown. Use additional paper if necessary. 1. The reaction N 2 + 3H 2 2NH 3 is run using g of N 2. How many moles of NH 3 are formed? a mol b mol c mol d mol 2. If 4.2 moles of NaNO 3 are used in the reaction 2NaNO 3 2NaNO 2 + O 2, how many grams of NaNO 2 are produced? a. 8.4 g b. 138 g c g d g

4 CHAPTER 9 HOMEWORK 9-4 (pp ) Complete each sentence. 1. The sum of the masses on the reactant side must equal 2. Mass-mass calculations are practical because 3. Given the mass of a substance and a chemical equation, the other data needed to solve a mass-mass problem are. 4. The inverted molar mass is equal to. SKILL BUILDER On a separate sheet of paper, solve the following problems. 1. Sodium reacts with chlorine gas to produce sodium chloride (table salt) in the following reaction: 2Na(s) + Cl 2 (g) 2NaCl(s). a. How many grams of sodium are required to produce g of salt? b. How many grams of Cl 2 are needed? 2. Calcium reacts with oxygen in air to produce calcium oxide in the reaction 2Ca(s) + O 2 (g) 2CaO(s). How many grams of oxygen gas must react to yield g of calcium oxide? 3. For the reaction 2LiOH + CO 2 Li 2 CO 3 + H 2 O(l), how many grams of H 2 O are produced when 49.2 g of LiOH are used? 4. Calcium chloride and sodium phosphate react to form solid calcium phosphate in the following reaction: 3CaCl 2 + 2Na 3 PO 4 Ca 3 (PO 4 ) 2 + 6NaCl. What mass of sodium phosphate is required to react completely with 9.75 g of calcium chloride? 1. Given the balanced equation 2C 4 H O 2 8CO H 2 O, how many moles of CO 2 are produced when 14.9 g of O 2 are used? a mol b mol c mol d mol 2. Which statement is true? a. The inverted molar mass is the conversion factor used to convert from moles to grams. b. The mass of a substance is expressed in moles. c. Moles and grams are units, while mass is a quantity. d. For any given chemical equation, all of the reactant is converted to product.

5 CHAPTER 9 HOMEWORK 9-5 (pp ) Define. 1. limiting reactant 2. excess reactant Answer the following question. 3. Write an analogy to explain the concept of limiting and excess reactants. (Two examples airplane seats and recipes are in your text.) GRAPHIC ORGANIZER On a separate sheet of paper, add reactant amounts and change answers as shown. 1. In the reaction Fe + 2 HCl FeCl 2 + H 2, what is the limiting reactant? 2. In the reaction PCl 5 + H 2 O H 3 P 4 + HCl, which is the limiting reactant? 3. Write the balanced equation that represents the reaction of sodium metal and water to produce sodium hydroxide and hydrogen gas. Identify the limiting reactant if 4.8 mol Na is exposed to 6.5 mol of water. 4. Write the balanced equation that represents the reaction of vinegar (HC 2 H 3 O 2 ) and baking soda (NaHCO 3 ) to produce carbon dioxide gas, water, and precipitate. Then identify the limiting reactant if g of vinegar is exposed to 84.0 g of baking soda. 1. Given the general chemical equation A + 2B 2C + D, what is the limiting reactant if 2.0 mol of A are exposed to 6.2 mol of B? a. A b. B c. C d. D 2. Given the general chemical equation 2A + 3B 2C + 6D, what is the excess reactant if 4.3 mol of A are exposed to 5.4 mol of B? a. A b. B c. C d. D

6 CHAPTER 9 HOMEWORK 9-6 (pp ) Answer each question. 1. What is the definition of actual yield? 2. What is the theoretical yield of a reaction? 3. What does a chemist find out by calculating the percent yield of a reaction that has gone to completion? 4. Write a general equation for calculating the percent yield. 5. For what reasons might the theoretical yield and actual yield differ? GRAPHIC ORGANIZER On a separate sheet of paper, create a chart to use as a reference for completing stoichiometric calculations. In your chart, list the different types of problems, such as mole mole, mole mass, mass mole, percent yield, and so on. Write the equations in a general way so that you can use the chart as you work in later chapters of the book. Be sure to use complete conversion factors. 1. Given the equation Cu 2 S + O 2 2Cu + SO 2, what is the theoretical yield of SO 2 if 8.20 g of O 2 are used? a g b g c g d. none of the above 2. If 4.2 mol of NH 3 and 6.8 mol of O 2 are used in the reaction 4NH 3 + 5O 2 4NO + 6H 2 O, then which of these statements is not true? a. O 2 is the excess reactant. b. The theoretical yield of H 2 O is grams. c. The theoretical yield of H 2 O is mol. d. The theoretical yield of NO is 1 mol.