Name: Period: By the end of the Unit 7, you should be able to: Chapter 12 1. Use stoichiometry to determine the amount of substance in a reaction 2. Determine the limiting reactant of a reaction 3. Determine the percent yield of a reaction Steps to Solving any Stoichiometry problem. 1. Balance the equation. 2. Convert given units to moles 3. Use the Mole Ratio 4. Convert from moles to the desired units. Mole to Mole: Answer the following questions. Be sure to show all your work and your units. (pg. 384-398) 1. How many moles of water are produced when 2.41 moles of methane are burned? CH 4 + O 2 CO 2 + H 2O 2. How many moles of chlorine gas are required to make 4.32 moles of NaCl? Na + Cl 2 NaCl 3. How many moles of both products are formed when 4.52 moles of calcium chloride reacts with silver nitrate? CaCl 2 + AgNO 3 AgCl + Ca(NO 3) 2 goldchemistry.wordpress.com Page 1
Grams to Moles or Moles to Grams: Answer the following questions. Be sure to show all your work and your units. (pg. 390-398) 4. The decomposition of potassium chlorate, KClO 3, is used as a source of oxygen in the laboratory. How many moles of potassium chlorate are needed to produce 15.00 grams of oxygen? KClO 3(s) KCl(s) + O 2(g) 5. In photosynthesis, plants use energy from the sun to produce glucose, C 6H 12O 6(s), and oxygen gas from the reaction of carbon dioxide and water. What mass, in grams, of glucose is produced when 3.00 mol of water react with carbon dioxide? CO 2 + H 2O O 2 + C 6H 12O 6 6. The first step in the industrial manufacture of nitric acid is the catalytic oxidation of ammonia. NH 3(g) + O 2(g) NO(g) + H 2O(g) The reaction is run using 824 g of NH 3 and excess oxygen. (a.) How many moles of NO are formed? (b.) How many moles of H 2O are formed? goldchemistry.wordpress.com Page 2
Grams to Grams: Answer the following questions. Be sure to show all your work and your units. (pg. 390-398) 7. How many grams of zinc chloride are formed when 26.21 g of zinc reacts with excess hydrogen chloride? 8. Oxygen was discovered by Joseph Priestly in 1774 when he heated mercury (II) oxide to decompose it into its constituent elements. HgO O 2 + Hg How many grams of mercury (II) oxide are needed to produce 125 g of oxygen? 9. How many grams of Fe 2O 3 are required to produce 200 grams of iron during the thermite reaction? Fe 2O 3 + Al Fe + Al 2O 3 Limiting Factor: Answer the following questions. Be sure to show all your work and your units. (pg. 400-403) 10. (a) How many moles of water would be produced if 4 moles of C 2H 4 reacted with 4 moles of oxygen gas to form water and carbon dioxide? (b) Which reactant was the limiting factor? goldchemistry.wordpress.com Page 3
(c) Which reactant was the excess factor? 11. Some rocket engines use a mixture of hydrazine, N 2H 4, and hydrogen peroxide, H 2O 2, as the propellant. The reaction is given by the following equation: N 2H 4(l) + H 2O 2(l) N 2(g) + H 2O (g) (a.) Which is the limiting reactant in this reaction when 0.750 mol of N 2H 4 is mixed with 0.500 mol of H 2O 2? (b.) How much of nitrogen, in moles, is formed? How many grams? (c.) How many grams of the excess reactant are left over? 12. (a). How many grams of Ca 3(PO 4) 2 can be produced from the reaction of 7.4 g Ca(OH) 2 with 9.8 g H 3PO 4? (b). How many grams of the excess is left over? goldchemistry.wordpress.com Page 4
Percent Yield: Answer the following questions. Be sure to show all your work and your units. (pg. 404-408) Actual Yield: Amount created during the experiment Theoretical Yield: Total amount that could have possibly been made % Yield = Actual Yield Theoretical Yield x 100 13. If a reaction occurs and 20 grams of sample are produced, what is the percent yield if theoretically 25 grams could have been made? 14. A 14.2 gram sample of potassium oxide reacted with excess water to produce 15.2 g of potassium hydroxide. What is the percent yield of KOH in this reaction? 15. A 15.6-gram sample of C 6H 6 reacts with excess HNO 3 to produce an actual yield of 18.0 grams of C 6H 5NO 2. What is the percent yield of C 6H 5NO 2 in this reaction? C 6H 6 + HNO 3 C 6H 5NO 2 + H 2O 16. A 120.5 gram sample of calcium sulfate reacted with 142.1 grams of silver chloride to produce 115.4 g of silver sulfate. What is the percent yield of silver sulfate in this reaction (Hint: this is also a limiting factor problem)? goldchemistry.wordpress.com Page 5