Questions from Previous Chemistry 115 Exams Stoichiometry

Questions from Previous Chemistry 115 Exams Stoichiometry -...

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Questions from Previous Chemistry 115 Exams Stoichiometry 1. Using the periodic table, predict what the proper empirical formula will be when magnesium reacts with fluorine to form an ionic solid. a. MgF 2 b. MgF c. Mg 2 F d. Mg 2 F 2 e. it cannot be determined. 2. How many grams does 4.00 moles of H 2 O weigh? a. 4.00 g b. 4.50 g c. 18.0 g d. 72.0 g e. 144.0 g 3. How many H 2 O molecules are there in a snow flake that weighs 4.0 x 10 -4 g? a. 1.3 x 10 19 b. 2.4 x 10 20 c. 2.2 x 10 -5 d. 6.02 x 10 23 e. it cannot be determined 4. If you take a 0.100 g dose of Vitamin C, C 6 H 8 O 6 , how many moles is this? a. 0.100 mol b. 5.68 x 10 -4 mol c. 17.61 mol d. 2.01 mol e. 6.84 x 10 -2 mol 5. For the following reaction, what is the stoichiometric coefficient for water that balances the reaction? N 2 O 5 + ___ H 2 O --> ___ HNO 3
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a. 1 b. 2 c. 3 d. 4 e. 5 6. For the following combustion reaction, what is the stoichiometric coefficient for oxygen that balances the reaction? C 3 H 8 + __ O 2 --> ___ H 2 O + ___ CO 2 a. 1 b. 2 c. 3 d. 4 e. 5 7. The following reaction: 2Mg + O 2 --> 2MgO can be classified as a a. Combustion reaction b. Acid-base reaction c. Decomposition reaction d. Combination reaction e. None of these 8. What is the percent composition of phosphorous in P 4 O 10 ? a. 10.9% b. 60.0% c. 43.6% d. 36.4% e. 100% 9. Consider the following (balanced) combustion reaction. If 16 g of CH 4 are consumed, what is the amount of H 2 O produced, in g? CH 4 + 2O 2 --> CO 2 + 2H 2 O MW CH 4 = 16 g/mol MW O 2 = 32 g/mol MW CO 2 = 44 g/mol MW H 2 O = 18 g/mol a. 64 g b. 32 g
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c. 18 g d. 36 g e. 44 g 10. What is the average mass of 10 aluminum atoms? a. 26.981 amu b. 1.624 x 10 -26 g c. 269.81 g d. 4.481 x 10 -22 g e. 1.661 x 10 -24 g 11. The common name for acetic acid is vinegar. The chemical formula is CH 3 CO 2 H. How many atoms of hydrogen are present in 35.00 moles of vinegar? a. 8.431 x 10 25 b. 2.108 x 10 25 c. 1.400 x 10 2 d. 1.744 x 10 -22 e. 2.401 x 10 24 12. In the balanced equation for the reaction: NH 3 (g) + O 2 (g) --> NO(g) + H 2 O(g) The coefficient for O 2 is: a. 1 b. 3 c. 5 d. 8 e. 10 13. What is the empirical formula of a compound that contains 30.43% N and 69.57% O? a. N 2 O b. NO c. NO 2 d. N 2 O 3 e. N 2 O 4
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14. Solid lithium hydroxide is used by NASA to remove (scrub) carbon dioxide from the spacecraft by reacting with the carbon dioxide to form solid lithium carbonate and liquid water. The balanced equation is: 2LiOH(s) + CO 2 (g) --> Li 2 CO 3 (s) + H 2 O(l) What mass of lithium carbonate will be formed by reacting 3.80 kg of lithium hydroxide with excess carbon dioxide? a. 3.80 kg b. 5.86 kg c. 11.7 kg d. 280 kg e. not enough information 15. Apatite is a mineral found in tooth enamel. When fluoride toothpastes are used, the mineral is converted to fluoroapatite, which is much harder and therfore more resistant to tooth decay. The formula for fluoroapatite is Ca 5 (PO 4 ) 3 F. What is the molecular weight?
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This note was uploaded on 02/12/2011 for the course CHEM 112 taught by Professor Sttaf during the Spring '03 term at Arkansas Pine Bluff.

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Questions from Previous Chemistry 115 Exams Stoichiometry -...

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