2. What is the mass percent of oxygen in H2SO4 (sulfuric acid)?
0 1% 2.04% 32.70% 65.26%
3. 6.02x1023 is....
a random number Avogadro's number stoichiometry percent yield None of these
4. A chemistry student was performing an experiment involving the following reaction: C3H8 (g) + O2 (g) --> CO2 (g) + H2O (g), balancing it with the coefficients 1, 5, 2, and 4 respectively. The oxygen was in excess. He used 20.18 grams of C3H8. When he measured the amount of CO2 produced, he was astounded to find that 46.22 grams were produced, 5.88 grams more than the theoretical yield of 40.34. What went wrong? Hint: Look at the formula
C3H8's coefficient should be 3, not 1 CO2's coefficient should be 3, not 2 O2's coefficient should be 3, not 5 Water's coefficient should be 3, not 4 None of these
5. There are 2.34 moles of substance A3 combined with 2.77 moles of substance B. Assume that the reaction goes to completion. After the reaction is complete, AB is reacted with substance C2. The reaction creates CB and A. If C2 was in excess during the second reaction, then how many moles of CB were produced?
2.43 moles 3.82 moles 4.38 moles 7.02 moles None of these
6. When 2 moles of propane (C3H8, MW = 44 grams) is combusted with oxygen gas, how many grams of CO2 (MW: 44 grams) are produced?
88 44 3 132 264
7. If 11 grams in a reaction was obtained, and you had a theoretical yield of 14 grams, what is your % yield?
0.79% 79% 11% 14% 12%
8. How many moles in 20 g of water?
1.11 20 18 1.1 42
9. Substance X has a mass of 36.08 grams. Calculations show that .199 moles of substance X exist. What element is most likely X?
Molybdenum Technetium Ruthenium Rhodium Palladium
10. Hydrochloric acid reacts with calcium carbonate yielding calcium chloride, water, and carbon dioxide. How many moles of calcium carbonate would be necessary to react with 8 moles of HCl?
1 2 3 4 5
11. There are two beakers sitting on a table. One contains 56.20 grams of water. The other contains hydrochloric acid (HCl). The number of atoms of hydrogen in the HCl equals the number of total atoms in the beaker full of water. How many grams of HCl are in the second beaker?
341.4 grams 142.4 g 938.1 g 53.29 g None of these
12. The empirical formula of a compound is C10H20 with a molar mass of 284 grams, find the molecular weight.
C20H40 C10H20 C5H10 C4H8 CH4
13. The combustion of butane (C4H10 with oxygen gas will yield carbon dioxide and water. Calculate the % yield of CO2 when 42 grams of butane are burned with 16.0 grams of oxygen and 10. grams of CO2 was formed.
25% 100% 32% 74% 64%
14. Substance A combines with substance B to form Substance AB. B is a diatomic molecule. You are given 3.15 moles of B2. If A is in excess, how many moles of AB are produced?
1.20 2.30 3.25 5.60 6.30
15. Balance the following equation (find what number coefficient X is): NH3 (g) + O2 (g) --> NO (g) + XH2O (g).
2 3 4 5 6
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