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Unformatted text preview: Version PREVIEW Homework 9 Savrasov (39825) 1 This printout should have 10 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. Expanding Gas 03 001 10.0 points A sample of ideal gas is expanded to twice its original volume of 0 . 4 m 3 in a quasistatic process for which P = V 2 with = 4 atm / m 6 , V a = 0 . 4 m 3 and V b = . 8 m 3 , as shown in the figure. V P P = ( 4 a t m / m 6 ) V 2 . 4 m 3 . 8 m 3 How much work was done by the expanding gas? Correct answer: 60509 . 9 J. Explanation: Given : = 4 atm / m 6 , V a = 0 . 4 m 3 , and V b = 0 . 8 m 3 . The work done by the gas is the area under the curve P = V 2 between V a and V b : W ab = integraldisplay b a P dV = integraldisplay b a V 2 dV = ( V 3 b V 3 a ) 3 = (4 atm / m 6 ) bracketleftbig (0 . 8 m 3 ) 3 (0 . 4 m 3 ) 3 bracketrightbig 3 = 60509 . 9 J . Gas Expands Isothermally 002 10.0 points Given: R = 8 . 31 J / K mol . 1 mol of an ideal gas expands isothermally at 373 K to 2 . 3 its initial volume. Find the heat flow into the system. Correct answer: 2581 . 71 J. Explanation: Given : n = 1 mol , R = 8 . 31 J / K mol , T = 373 K , and V f = 2 . 3 V i . This is an isothermal process, so the inter nal energy of the ideal gas is constant. Thus the heat flowing into the system is equal to the work done to the system: W = nRT ln parenleftbigg V f V i parenrightbigg = (1 mol) (8 . 31 J / K mol) (373 K) ln(2 . 3) = 2581 . 71 J ....
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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
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