Henan Experimental High School
Sino-Canadian Program
Chemistry 11 Test 2
Unit 1: Stoichiometry
Time: 50 minutes
__________________________________________________________________________
GENERAL INFORMATION
Name:
Teacher’s Name:
Student Number:
Date:
Instruction: Read the questions carefully. Use the answer sheet to answer all the questions.
Section A
Molecular Formula
Problem # 1
A 100 gram sample of a compound has the following composition by mass: 60.0 % C, 12.0
% H and 28.0 % N.
1. How many grams of hydrogen and nitrogen are present in the sample?
a.
b.
c.
d.
H- 12 g, N- 18 g
H- 12.5 g, N- 20 g
H- 12 g, N- 28 g
H- 60 g- N- 28 g
2. What is the empirical formula of the compound?
a.
b.
c.
d.
C5H11N3
C5H12N2
C4H12N
C5H12N4
3. If this compound has a molar mass of 300 g/mol, what is its molecular formula?
a.
b.
c.
d.
C15H38N6
C15H36N6
C14H36N6
C14H34N6
Section B
Stoichiometry Calculations
Problem # 2
Given the following reaction: N2O4
+ 2N2H4 → 3N2 + 4H2O
92.02 g
64.12 g
84.06 g 72.08 g
4. How many grams of N2H4 react with 75.62 g of N2O4?
a.
b.
c.
d.
52.69 g N2H4
50.30 g N2H4
55.60 g N2H4
54.36 g N2H4
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Chemistry 11
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5. How many mol of H2O are produced by reacting 7.5 mol of N2H4?
a.
b.
c.
d.
13 mol H2O
12.5 mol H2O
15 mol H2O
17 mol H2O
6. How many grams of N2O4 are needed to react with 3.65 mol of N2H4?
a.
b.
c.
d.
167.9 g N2O4
157.5 g N2O4
162.7 g N2O4
169.8 g N2O4
7. How many molecules of N2O4 are needed to react with 58.65 g of N2H4?
a.
b.
c.
d.
5.5 X 1022 molecules N2O4
6.5 X 1023 molecules N2O4
5.5 X 1023 molecules N2O4
5.0 X 1023 molecules N2O4
Section C
Limiting Reagent
Problem # 3
Given the following reaction:
P4
1 mol
123.88 g
47.35 g
+
5O2
→
5 mol
160 g
123.45
P4O10
1 mol
283.88 g
?
8. According to the above chemical reaction, what is the maximum mass of P4O10 that can be
made?
a.
b.
c.
d.
100.5 g P4O10
115.5 g P4O10
108.5 g P4O10
101.5 g P4O10
9. Which of the following statements about the limiting reagent and the excess reagent of the
above chemical reaction is true?
a.
b.
c.
d.
P4 is the limiting reagent, O2 is the excess reagent
O2 is the limiting reagent, P4 is the excess reagent
The above chemical reaction is an example of decomposition reaction
The mass of reactant in excess is twice larger than the mass of the limiting reagent.
10. How many grams of the reactant that is in excess will be left over unreacted?
a.
b.
c.
d.
65.3 g
55.3 g
62.3 g
60.3 g
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Chemistry 11
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Section D
Percent Yield
Problem # 4
Given the reaction:
2H2 +
2 mol
4.04 g
O2 
1 mol
32 g
2H2O
2 mol
36.04 g
11. What is the theoretical yield of H2O if 16 grams H2 reacts with 10 grams of O2?
a. 10.26 g H2O
b. 13.26 g H2O
c. 12.26 g H2O
d. 11.26 g H2O
12. What is the % yield of H2O if 138 g H2O is produced from 16 g H2 and excess O2?
a. 97.5%
b. 95.7%
Problem # 5
The electrolysis of water forms H2 and O2
c. 90%
2H2O
36.04 g
d. 96.7%

2H2 + O2
4.04 g 32 g
13. What is the % yield of O2 if 12.3 g of O2 is produced from the decomposition of 14.0 g
H2O?
a. 98.95%
b. 97.95%
c. 99.95%
d. 96.95%
Problem # 6
Ammonia is produced from combining hydrogen and nitrogen:
3H2
+
N2

2NH3
6.06 g
28.02 g
34.08 g
14. What is the theoretical yield of NH3 if 40.4 g H2 reacts with excess N2?
a. 127.2 g NH3
b. 200.2 g NH3
c. 227.2 g NH3
d. 230.2 g NH3
15. What is the % yield of NH3 if 40.5 g NH3 is produced from 40.4 g H2 and excess N2?
a. 17.83 %
b. 20.83 %
c. 19.83 %
d. 16.83 %
Section E
Avogadro’s Hypothesis and Mole Concept Applied to Gases
16. What volume will 0.750 moles of nitrogen gas occupy at STP?
a. 16.8 liters
b. 15 liters
c. 14.8 liters
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d. 17.5 liters
Chemistry 11
TEST
17. Calculate how many methane (CH4) molecules are there in 4.48 dm3 of the gas at STP?
a. 2.8 X 1023
b. 1.8 X 1023
c. 1.2 X 1023
d. 1.5 X 1023
Problem # 7
Methanol (CH3OH) can be used as fuel in a fondue burner. CH3OH has to react with O2 in air
to produce H2O and CO2.
__CH3OH
+
__O2

__H2O
+ __CO2
18. In which type of chemical reaction does the above reaction belong?
a. Combination
b. Decomposition
c. Combustion
d. Displacement
19. To balance the above equation, reactants and products should have this order of
coefficients:
a. 2, 3, 4, 2
b. 2, 3, 2, 2
c. 2, 3, 4, 2
d. 2,3,3,2
20. Given the above chemical reaction, what volume of oxygen at STP is needed to
completely burn 0.46 mol of methanol (CH3OH)?
a. 14 liters
b. 15.46 liters
c. 17 liters
d. 16.5 liters
21. Which of the following statements about Avogadro’s hypothesis is not true?
a. At STP, mole of a given gas is equal to its volume at STP divided by the molar volume
of gases at STP.
b. At STP, equal amount of gases occupies equal volume.
c. At STP, 32 grams of O2 and 2.0 grams H2 occupies same volume.
d. At STP, 32 grams of O2 and 32 grams CO2 contains same number of molecules.
Section F
(Write your answer to this question on the answer sheet)
Give at least three reasons why actual yield is lesser than the theoretical yield. (4 marks)
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Chemistry 11
TEST