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Unformatted text preview: Version PREVIEW Homework 10 Savrasov (39825) 1 This printout should have 13 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. Carnot Efficiency 001 10.0 points A heat engine operates between two reservoirs at 18 . 9 C and 168 C. What is the maximum efficiency possible for this engine? Correct answer: 0 . 338095. Explanation: Given : T h = 168 C = 441 K and T c = 18 . 9 C = 291 . 9 K . Efficiency e = 1 T c T h = 1 291 . 9 K 441 K = . 338095 . Entropy in Expansion 002 10.0 points 58 . 1 mol of an ideal gas is allowed to undergo a free expansion. If the initial volume is 20 cm 3 and the final volume is 100 cm 3 , find the change in entropy. Correct answer: 777 . 054 J / K. Explanation: Given : n = 58 . 1 mol , V 1 = 20 cm 3 , and V 2 = 100 cm 3 . The free expansion is not quasistatic; we have to use a quasistatic process connecting the initial and the final equilibrium states to calculate the change of entropy. Since the two states have the same temperature, we connect them with an isothermal process which gives S = nR ln parenleftbigg V 2 V 1 parenrightbigg = (58 . 1 mol)(8 . 31 J / mol K) ln parenleftbigg 100 cm 3 20 cm 3 parenrightbigg = 777 . 054 J / K ....
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This note was uploaded on 01/10/2010 for the course PHY na taught by Professor Richardscalettar during the Fall '09 term at UC Davis.
 Fall '09
 RichardScalettar
 Work, Heat

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