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Homework Help: Entropy Change of an expanding gas

  1. May 22, 2008 #1
    Two moles of an ideal gas undergo a reversible isothermal expansion from 1.97×10−2 m^3 to 4.82×10−2 m^3 at a temperature of 20.0 C.

    What is the change in entropy of the gas?


    Using [tex]\Delta[/tex]S = nRIn(V2/V1)

    = 2(8.31*ln(4.82*10^-2/1.97*10^-2)

    ANS = -138.20 J/K

    Is this correct? I can only enter it once on my website and I want to make sure this is right first time :)
    Last edited: May 22, 2008
  2. jcsd
  3. May 22, 2008 #2


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    Homework Helper

    Hi cmcc3119,

    I think you made a math error in your calculation; I don't think that number follows from the line above it.
  4. May 22, 2008 #3
    Yep I figured out the right anwer which is 14.9

    I don't know what I meant with that massive negative figure! Thanks for you help anyway.
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