REVIEW: Stoichiometry / Percent Yield / Limiting Reagent
Stoichiometry
1. Using the following equation: 2 NaOH + H2SO4  2 H2O + Na2SO4
How many grams of sodium sulfate will be formed if you start with 200
grams of sodium hydroxide and you have an excess of sulfuric acid?
2. Using the following equation: Pb(SO4)2 + 4 LiNO3  Pb(NO3)4 + 2 Li2SO4
How many grams of lithium nitrate will be needed to make 250 grams of
lithium sulfate, assuming that you have an adequate amount of lead (IV)
sulfate to do the reaction?
Percent Yield
1. A reaction occurs between 500.0 g of carbon disulfide and an excess
amount of oxygen gas. Sulfur dioxide and carbon dioxide are produced.
a. Write the balanced chemical equation.
b. Determine the theoretical yield of sulfur dioxide using stoichiometry.
c. If 768 g of sulfur dioxide is produced, what is my percent yield?
2. If I start this reaction with 40 grams of magnesium and an excess of
nitric acid, how many grams of hydrogen gas will I produce?
a. Write the BCE: Mg + HNO3  Mg(NO3)2 + H2
b. Determine the theoretical yield of hydrogen gas.
c. If 1.7 grams of hydrogen is actually produced, what was my percent
yield of hydrogen?
Limiting Reagent
1. What is the limiting reactant when 1.5 g of hydrogen react with 0.5 g of
oxygen to produce water?
a. Write the BCE.
b. What mass of water is produced?
c. What is the limiting reagent?
2. Consider the following reaction: 3 NH4NO3 + Na3PO4  (NH4)3PO4 + 3 NaNO3
a. Assume we started with 30 grams of ammonium nitrate and 50 grams of
sodium phosphate. What mass of NaNO3 can be formed?
b. What is the limiting reagent?
Stoichiometry TEST question
1. Use what you know about stoichiometry to solve this problem.
a. Write the balanced equation for the reaction of acetic acid (C2H4O2) with aluminum hydroxide to form
water and aluminum acetate:
b. Using the equation from problem #1, determine the mass of aluminum acetate that can be made if I
do this reaction with 125 grams of acetic acid and 275 grams of aluminum hydroxide.
c. What is the limiting reagent in problem #2?
d. When I actually did this experiment in the lab, I obtained 123.5g of the aluminum acetate product.
What is my percent yield for this reaction?
e. How much of the excess reagent will be left over after the reaction is complete?
1. Use what you know about stoichiometry to solve this problem.
a. Write the balanced equation for the reaction of acetic acid (C2H4O2) with aluminum hydroxide to
form water and aluminum acetate:
3 C2H3O2H + Al(OH)3  Al(C2H3O2)3 + 3 H2O
b. Using the equation from part a, determine the mass of aluminum acetate that can be made if I do
this reaction with 125 grams of acetic acid and 275 grams of aluminum hydroxide.
c. What is the limiting reagent in part b?
Acetic acid.
d. When I actually did this experiment in the lab, I obtained 123.5g of the aluminum acetate product.
What is my percent yield for this reaction?
% yield = 123.5 g Al(C2H4O2)3 x 100 = 87.6%
141.0 g Al(C2H4O2)3
e. How much of the excess reagent will be left over after the reaction is complete?
141 g Al(C2H3O2)3 x 1 mol Al(C2H3O2)3 x 1 mol Al(OH)3
x 78 g Al(OH)3
204 g Al(C2H3O2)3
1 mol Al(C2H3O2)3 1 mol Al(OH)3
275 g Al(OH)3 - 53.9g Al(OH)3 = 221 g Al(OH)3
= 53.9g Al(OH)3