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Unformatted text preview: maldonado (om2892) ch 9 and 10 review hoener (53115) 1 This print-out should have 29 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. THIS IS A REVIEW OPPORTUNITY ONLY - IT IS NOT HOMEWORK, CAN NOT AND WILL NOT BE USED TOWARD YOUR COURSE GRADE OR BONUS POINTS! OF ANY KIND! (It is an old exam from my other section made into a review opportunity.) 001 10.0 points All of the following are state functions EX- CEPT 1. U 2. T 3. q correct 4. H Explanation: State functions are denoted by capital- ized letters. They are P (ressure), V (olume), T (emperature), S (entropy), G (ibbs Free en- ergy), H (enthalpy). The change in the value of a state function is independent of the path taken. 002 10.0 points The dramatic temperature changes on the moon between day and night are not seen on the Earth because of what property of water? 1. less dense as a solid 2. excellent solvent 3. All of these contribute. 4. high heat capacity correct Explanation: 003 10.0 points Which molecules of the following gases will have the greatest average kinetic energy? 1. All of the molecules have the same kinetic energy. correct 2. H 2 at 0.5 atm and 298 K 3. He at 0.1 atm and 298 K 4. N 2 at 1 atm and 298 K 5. CO 2 at 1 atm and 298 K Explanation: From kinetic molecular theory, the temper- ature is directly proportional to mean KE. If all of the gases are at the same tempera- ture they have the same average KE. (Note: The average speeds will be different since they have different molecular weights.) 004 10.0 points For the methanol combustion reaction 2 CH 3 OH( ) + 3 O 2 (g)- 2 CO 2 (g) + 4 H 2 O(g) estimate the amount of P V work done and tell whether the work was done on or by the system. Assume a temperature of 27 C. 1. 7.5 kJ, work done on the system 2. 2.5 kJ, work done on the system 3. No work is done in this reaction. 4. 7.5 kJ, work done by the system correct 5. 2.5 kJ, work done by the system Explanation: T = 27 C + 273 = 300 K Considering only moles of gas, n = n f- n i = (2 + 4)- 3 = 3 . w =- nRT =- (3 mol) (8 . 314 J / mol K) (300 K) =- 7500 J =- 7 . 5 kJ The system expands because n is positive, so the system does the work on the surround- ings. Also, when w is negative, work is done by the system. maldonado (om2892) ch 9 and 10 review hoener (53115) 2 005 10.0 points Which of the following statements is true about an exothermic reaction? 1. The change in enthalpy is positive. 2. The energy of the products is higher than that of the reactants. 3. We can determine the absolute heat con- tent of the products and reactants. 4. Heat is evolved during the reaction. cor- rect Explanation: Exothermic reactions release energy from the system into the surroundings....
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- Spring '07