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Unit 8 Test Review
Stoichiometry/Limiting Reatants
Name _________________________
Date __________ Hour _______
Answer the following questions completely. Show all work. Be sure to watch your significant
figures and put proper units on your answers.
1. What is stoichiometry?
2. What is meant by a “limiting reactant”?
3. Explain why it is often necessary to determine the percent yield of a reaction.
4. Camels store the fat tristearin (C57H110O6) in the hump. Besides being a source of energy, the
fat is a source of water for the camel because when the fat is burned, the following reaction
occurs:
2 C57H110O6 (s) + 163 O2 (g)  114 CO2 (g) + 110 H2O (l)
a) Determine the molar mass of tristearin. Show your work and include proper units.
b) Determine the mass of tristearin needed to produce 45200 g of water.
c) If 9320 g of tristearin react with 16100 L of oxygen gas, what mass of water can form?
5. Use the following balanced equation:
CO(g) + H2O(l)  CO2(g) + H2(g)
In a laboratory test, 27.8 g CO and 48.2 g H2O are placed in a container to be reacted.
a) Explain how the following calculation helps to determine the limiting reactant for this
reaction. Tell what the limiting reactant is.
1 mol CO 1 mol H 2O 18.0 g H 2O
27.8 g CO 


 17.9 g H 2O
28.0 g CO 1 mol CO 1 mol H 2O
b) Determine the volume of carbon dioxide formed in the reaction described above.
6. Balance the following equation:
N2H4 +
N2O4 
N2 +
H2 O
In a laboratory test, 27.3 g N2H4 and 51.3 g N2O4 are placed in a container to be reacted.
a) Explain how the following calculations help to determine the limiting reactant for this
reaction. Tell what the limiting reactant is.
1mol N 2 H 4
3 mol N 2
27.3 g N 2 H 4 

 1.28 mol N 2
32.0 g N 2 H 4 2 mol N 2 H 4
1mol N 2O4
3 mol N 2
51.3 g N 2O4 

 1.67 mol N 2
92.0 g N 2O4 1mol N 2 H 4
b) Determine the mass of water that can form from the above reaction.
c) Determine the mass of excess reactant that remains in the above reaction.
7. Use the following balanced equation:
3 Mn3O4 (s) + 8 Al (s)  4 Al2O3 (s) + 9 Mn (s)
In a laboratory test, 19.2 g Mn3O4 and 4.72 g Al are placed in a container to be reacted.
a) Explain how the following calculation helps to determine the limiting reactant for this
reaction. Tell what the limiting reactant is.
1mol Mn3O4
8 mol Al
27.0 g Al
19.2 g Mn3O4 


 6.04 g Al
228.7 g Mn3O4 3 mol Mn3O4 1mol Al
b) Determine the mass of aluminum oxide that can form in the above reaction.
c) If 7.93 g of aluminum oxide actually form when the above reaction is performed, what is the
percent yield?
8. Aluminum reacts with oxygen gas to produce aluminum oxide:


4 Al + 3 O2  2 Al2O3
In the box on the left, sketch 10 atoms of aluminum and 6 molecules of oxygen.
In the box on the right, sketch the contents after the reaction of the particles occurs according to
the balanced equation.
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a) What it the limiting reactant?
_______________________
b) What is the excess reactant?
_______________________
c) How many atoms or molecules of excess reactant remain? _______________________
9. A student placed a piece of nickel into a beaker containing silver nitrate solution. Solid silver metal
and aqueous nickel (II) nitrate were produced. After allowing the reaction to proceed for a few
minutes, the nickel is removed and the silver that formed is filtered out using a funnel and filter paper.
The following data values were collected:
Mass of nickel before reaction
Mass of nickel after reaction
Mass of filter paper
Mass of filter paper with silver
5.00 g
4.69 g
1.01 g
2.13 g
a) Write a balanced equation for the reaction that occurs.
b) What mass of nickel reacted, according to the data.
____________
c) Based on the mass of nickel that reacted, what is the theoretical yield of silver?
d) What mass of silver is formed, according to the data.
e) What is the percent yield of silver in this reaction?
____________