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Stoichiometric Problems – Test
1. Nitric acid is formed by the reaction of nitrogen dioxide and water.
3NO2 (g) + H2O (l)  NO (g) + 2HNO3 (g)
How many moles of water are needed to react with 8.4 mol NO2?
A. 2.8 mol
C. 8.4 mol
B. 3.0 mol
D. 25 mol
2. Phosphorus trifluoride is formed from its elements.
P4 (s) + 6F2 (g)  4PF3 (g)
How many grams of fluorine are needed to react with 6.20 g of phosphorus?
A. 2.85 g
C. 11.4 g
B. 5.70 g
D. 37.2 g
3. Calculate the molar mass of ammonium phosphate, (NH4)3PO4.
A. 113.0 g/mol
C. 149.0 g/mol
B. 121.0 g/mol
D. 242.0 g/mol
4. Based on the structural formula below, what is the empirical formula for tartaric acid, a compound
found in grape juice.
A. C2H3O6
C. CHO
B. C4H6O6
D. C1H1.5O1.5
5. Which of these compounds has the largest percent by mass of nitrogen?
A. N2O
C. NO2
B. NO
D. N2O3
6. Which of these statements is true of a balloon filled with 1.00 mol N2 (g) at STP?
A. I only
C. I and III only
B. I and II only
D. I, II, and III
7. Allicin, C6H10S2O, is the compound that gives garlic its odor. A sample of allicin contains 3.0 x 1021
atoms of carbon. How many hydrogen atoms does this sample contain?
A. 10
C. 1.8x1021
B. 1.0x1021
D. 5.0x1021
The lettered choices below refer to Questions 8-11. A lettered choice may be used once, more than once,
or not at all.
A. CH
B. CH2
C. C2H5
D. CH3
E. C2H3
8. C8H12
9. C6H6
10. C2H6
11. C4H10
For questions 12-14, write the molecular formula for each compound whose structural formula is shown.
15. How many moles of oxygen are produced by the decomposition of 1225 grams of potassium
chlorate (KClO3)?
2KClO3 (s)  2KCl (s) + 3O2 (g)
24
A. 3.06x10 molecules O2
C. 4.78x1024 molecules O2
B. 9.03x1024 molecules O2
D. 1.09x1024 molecules O2
16. How many liters of oxygen are needed to burn 10 liters of carbon monoxide?
2CO (g) + O2 (g)  2CO2 (g)
A. 15 L O2
C. 2.5 L O2
B. 5 L O2
D. 8 L O2
For Questions 17-18.
17. How many moles of chlorine gas (Cl2) would react with 5 moles of sodium (Na) according to the
following chemical equation? (Balance the equation first.)
A. 2.5 mol Cl2
B. 5.0 mol Cl2
Na + Cl2  NaCl
C. 3.5 mol Cl2
D. 4.0 mol Cl2
18. What mass of Na must be used to produce 29.2 g of NaCl?
A. 10.31 g
B. 12.16 g
C. 22.4 g
D. 11.5 g
19. How many moles of oxygen are required to react completely with 14.8 moles of aluminum?
4Al (s) + 3O2 (g)  2Al2O3 (s)
A. 0.52 mol
B. 8.67 mol
C. 11.1 mol
D. 9.14 mol
Write the final answer inside the box.
20. A. Caffeine is a compound found in some natural coffees and teas and in some colas. Determine
the empirical formula for caffeine using the following composition:
49.47 grams C, 28.85 g N, 16.48 grams O, and 5.20 grams H
B. If the molar mass of caffeine is 194.19 g/mol, calculate its molecular formula.