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Chem1A-Fa10-FinalReview

Chem1A-Fa10-FinalReview - Selected Practice Problems for...

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Selected Practice Problems for Comprehensive Final Exam Chem 1A Fall 2010 1. Enthalpy of Reaction . Calculate the standard heat of reaction H rxn º for the combustion of ethylene below. Refer to Appendix 4 of your textbook for standard heats of formation. C 2 H 4 (g) + 3 O 2 (g) 2 CO 2 (g) + 2 H 2 O (g) H rxn º = ? 2. Stoichiometry. Acetylene, C 2 H 2 , is a gas commonly used in welding. Calculate the number of kilojoules released by the combustion of 5.00 L of acetylene at 25 ºC, 1.25 atm. 2 C 2 H 2 (g) + 5 O 2 (g) 4 CO 2 (g) + 2 H 2 O (g) H rxn º = –2512.4 kJ 3. Hess’s Law. Sulfuric acid is one of the most commonly manufactured industrial chemicals. It is produced by reacting sulfur, S 8 , with oxygen gas and then with water in a series of three reactions: S 8 (s) + 8 O 2 (g) 8 SO 2 (g) H 1 º = –2374.4 kJ 2 SO 2 (g) + O 2 (g) 2 SO 3 (g) H 2 º = –197.8 kJ SO 3 (g) + H 2 O (l) H 2 SO 4 (l) H 3 º = –132.5 kJ Write the overall reaction and calculate the overall enthalpy change Δ rxn for this process.
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4. Heat of Solution. Adding water to certain anhydrous salts releases considerable energy.
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