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Homework Help: Ideal Gas Law Problem

  1. Apr 22, 2014 #1
    1. The problem statement, all variables and given/known data

    A cylinder fitted with a movable piston contains ideal gas at 27C, pressure .5 x 10^5 Pa, and volume 1.25 m^3. What will be the final temperature if the gas is compressed to .8 m^3 and the pressure rises to .82 x 10^5 Pa.

    A) 125 C
    B) 154 C
    C) 246 C
    D) 67.7 C
    E) 41.8 C

    2. Relevant equations


    3. The attempt at a solution

    I thought this problem was going to be pretty simple. (.5 x 10^5 Pa x 1.25 m^3)/27 = (.82 x 10^5 Pa x .8 m^3)/T2. I keep getting T2 is equal to 28.3392. Is there something I'm missing? It seems like the pressure/volume ratio doesn't change that drastically so the temperatures would be close but the closest answer is at ~15 C increase. Any help is appreciated.
  2. jcsd
  3. Apr 22, 2014 #2
    You have to use absolute temperatures.

  4. Apr 22, 2014 #3
    Got it. I thought since it was ratios the units wouldn't affect the final outcome but I was wrong.
  5. Apr 22, 2014 #4
    Only when you're talking about temperature DIFFERENCES - not ratios - you may replace Kelvins with Celsius.
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