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Calculating isothermal copressibility and expansion coefficient

  1. Sep 19, 2009 #1
    1. The problem statement, all variables and given/known data
    Calculate the isothermal compressibility and the expansion coefficient of a van der waals gas. Then show using Euler's chain relation that KR = alpha(Vm-b)


    2. Relevant equations
    isothermal compressibility K = (-1/V) (dv/dp)t
    isothermal expansion alpha= (1/v)(dv/dt)p


    3. The attempt at a solution
    I realize it has to do with partial derivatives. But beyond this i'm lost.
     
  2. jcsd
  3. Sep 19, 2009 #2

    gabbagabbahey

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    Homework Helper
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    Hi Zcuttlefish, welcome to PF!:smile:

    Hint: You might start by looking up the equation of state for a Van Der Waals gas!:wink:
     
  4. Sep 19, 2009 #3
    I did (p+ a/V2)(v-b) = RT
    (not including n because it should be constant)


    my answer for dv/dp ended up looking like
    Then i used the product rule and took the derivative dv/dp of the terms. I'm still unsure of why or if i've even gotten closer to the answer.

    V3(v-b)/(2a(v-b)2-RTV3)
    I seem to be missing an R on top.
     
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