Download Practice: Chapter 11

11.1 Defining Stoichiometry
Practice Problems
1. Interpret each balanced equation in terms of particles, moles, and mass. Show that the law of conservation of mass is observed.
a. 2H2O2(l)  O2(g) + 2H2O(l)
b. H2CO3(aq)  H2O(l) + CO2(g)
c. 4HCl(aq) + O2(g)  2H2O(l) + 2Cl2(g)
2. Determine all the mole ratios for the following balanced chemical equations.
a. N2(g) + O2(g)  2NO(g)
b. 4NH3(aq) + 5O2(g)  4NO(g) + 6H2O(l)
c. 4HCl(aq) + O2(g)  2H2O(l) + 2Cl2(g)
11.2 Stoichiometric Calculations
Practice Problems
3. The carbon dioxide exhaled by astronauts can be removed from a spacecraft by reacting it with lithium hydroxide (LiOH). The reaction
is as follows: CO2(g) + 2LiOH(s)  Li2CO3(s) + H2O(l). An average person exhales about 20 moles of CO2 per day. How many moles of
LiOH would be required to maintain two astronauts in a spacecraft for three days?
4. Balance the following equation and answer the questions below.
KClO3(s)  KCl(s) + O2(g)
a. How many moles of O2 are produced from 10 moles of KClO3?
b. How many moles of KCl are produced using 3 moles of KClO3?
c. How many moles of KClO3 are needed to produce 50 moles
of O2?
5. Calculate the mass of sodium chloride (NaCl) produced when 5.50 moles of sodium reacts in excess chlorine gas.
6. How many grams of chlorine gas must be reacted with excess sodium iodide (NaI) to produce 6.00 moles of sodium chloride?
a. Balance the equation: NaI(aq) + Cl2(g)  NaCl(aq) + I2(s).
b. Perform the calculation.
7. Calculate the mass of hydrochloric acid (HCl) needed to react with 5.00 moles of zinc.
a. Balance the equation: Zn(s) + HCl(aq)  ZnCl2(aq) + H2(g).
b. Perform the calculation.
Practice Problems
8. Balance each equation and solve the problem.
a. If 40.0 g of magnesium reacts with excess hydrochloric acid (HCl), how many grams of magnesium chloride (MgCl 2) are produced?
Mg(s) + HCl(aq)  MgCl2(aq) + H2(g)
b. Determine the mass of copper needed to react completely with a solution containing 12.0 g of silver nitrate (AgNO 3).
Cu(s) + AgNO3(aq)  Cu(NO3)2(aq) + Ag(s)
c.
How many grams of hydrogen chloride (HCl) are produced when 15.0 g of sodium chloride (NaCl) reacts with excess sulfuric acid
(H2SO4)?
NaCl(aq) + H2SO4(aq)  Na2SO4 + HCl(g)
d.
Calculate the mass of silver phosphate (Ag3PO4) produced if 30.0 g of silver acetate (AgCH3COO) reacts with excess sodium
phosphate (Na3PO4).
AgCH3COO(aq) + Na3PO4(aq)  Ag3PO4(s) + NaCH3COO(aq)
11.3 Limiting Reactants
In the reaction below, 40.0 g of sodium hydroxide (NaOH) reacts with 60.0 g of sulfuric acid (H2SO4).
2NaOH(aq) + H2SO4(aq)  Na2SO4 + 2H2O(g)
a. Which reactant is the limiting reactant?
b. What mass of Na2SO4 can be produced using the given quantities of the reactants?
9. Ammonia (NH3) is one of the most common chemicals produced in the United States. It is used to make fertilizer and other products.
Ammonia is produced by the following chemical reaction.
N2(g) + 3H2(g)  2NH3(g)
a. If you have 1.00103 g of N2 and 2.50103 g of H2, which is the limiting reactant in the reaction?
b. How many grams of ammonia can be produced from the amount of limiting reactant available?
c. Calculate the mass of excess reactant that remains after the reaction is complete.
10. Aluminum reacts with chlorine to produce aluminum chloride.
a. Balance the equation: Al(s) + Cl2(g)  AlCl3(s).
b. If you begin with 3.2 g of aluminum and 5.4 g of chlorine, which is the limiting reactant?
c. How many grams of aluminum chloride can be produced from the amount of limiting reactant available?
d. Calculate the mass of excess reactant that remains after the reaction is complete.
11.4 Percent Yield
Aspirin (C9H8O4) can be made from salicylic acid (C7H6O3) and acetic anhydride (C4H6O3). Suppose you mix 13.2 g of salicylic acid with an
excess of acetic anhydride and obtain 5.9 g of aspirin and some water. Calculate the percent yield of aspirin in this reaction.
2C7H6O3(s) + C4H6O3(l)  2C9H8O4(s) + H2O(l)
Practice Problems
11. Calculate the percent yield for each chemical reaction based on the data provided.
a. theoretical yield: 25 g; actual yield: 20 g
b. theoretical yield: 55 g; actual yield: 42 g
c. theoretical yield: 5.2 g; actual yield: 4.9 g
12. Calculate the actual yield for each chemical reaction based on the data provided.
a. theoretical yield: 20 g; percent yield: 95%
b. theoretical yield: 75 g; percent yield: 88%
c. theoretical yield: 9.2 g; percent yield: 62%
13. In an experiment, 10.0 g of magnesium reacted with excess hydrochloric acid forming magnesium chloride.
Mg(s) + 2HCl(aq)  MgCl2(aq) + H2(g)
At the completion of the reaction, 29.5 g of magnesium chloride was produced. Calculate the theoretical yield and the percent yield.
Chapter 11 Review
14. What is stoichiometry?
15. Write two questions that stoichiometry can help you answer about the following chemical equation.
4HCl(aq) + O2(g)  2H2O(l) + 2Cl2(g)
16. Relate the law of conservation of mass to stoichiometry.
17. What is the difference between a limiting reactant and an excess reactant?