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What does translational energy have to do with entropy change?

  1. Mar 1, 2007 #1
    I know that the translational energy of gas can be represented by
    3/2NkT
    where N = number of molecules, k = boltzmann's constant, T = temperature

    my textbook says that the change in entropy is
    (delta)S = (integral from 1 to 2) dS = (integral from 1 to 2) dU/T + (integral from 1 to 2) PdV/T = NRln(v2/v1)

    i know that since U = 0 in an isothermal system, dU/T term gets cancelled and the PdV/T term is left, but i don't understand how we get NRln(v2/v1) from it

    i also dont know how translational energy comes in to place.

    much help needed!
     
  2. jcsd
  3. Mar 8, 2007 #2
    Try using the ideal gas law PV = NRT to put the P/T in terms of V. Hope this helps.
     
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