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Unformatted text preview: Patel, Kinal – Homework 23 – Due: Dec 4 2007, 7:00 pm – Inst: D Weathers 1 This printout should have 11 questions. Multiplechoice questions may continue on the next column or page – find all choices before answering. The due time is Central time. 001 (part 1 of 1) 10 points During a controlled expansion, the pressure of a gas is P = 12 e b V atm where b = 0 . 084734 m 3 and the volume is in m 3 . Determine the work performed when the gas expands from 7 . 8 m 3 to 52 . 2 m 3 . Correct answer: 7 . 23558 MJ. Explanation: Given : V i = 7 . 8 m 3 , V f = 52 . 2 m 3 , and b = 0 . 084734 m 3 . The work done is W = Z V f V i P dV = (12 atm) e b V f e b V i b = 12 atm . 084734 m 3 101300 Pa 1 atm × h e ( . 084734 m 3 )( 52 . 2 m 3 ) e ( . 084734 m 3 )( 7 . 8 m 3 ) i × 1 MJ 10 6 J = 7 . 23558 MJ . keywords: 002 (part 1 of 1) 10 points Given: R = 8 . 31451 J / mol · K . A sample of helium behaves as an ideal gas as it is heated at constant pressure from 263 K to 393 K. If 50 J of work is done by the gas during this process, what is the mass of the helium sample? Correct answer: 0 . 185033 g. Explanation: Given : T i = 263 K , T f = 393 K , W = 50 J , M = 4 g / mol , and R = 8 . 31451 J / mol · K . The work done by the gas is W by gas = P (Δ V ) = P V f P V i = nRT f nRT i = nR Δ T and the difference in temperature is Δ T = T f T i = 393 K 263 K = 130 K . Thus n = W by gas R Δ T and the mass of helium is m = nM = W by gas M R Δ T = (50 J)(4 g / mol) (8 . 31451 J / mol · K)(130 K) = . 185033 g . keywords: 003 (part 1 of 2) 10 points An ideal gas is compressed to half its original volume while its temperature is held constant....
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 Spring '07
 Weathers
 Thermodynamics, Energy, Work, Heat, patel

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