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Homework Help: Thermodynamics: Heat capacity

  1. May 9, 2012 #1
    1. The problem statement, all variables and given/known data
    The temperature of one mole of ideal gas is 360K. The gas is allowed to expand adiabatically to the double volume. Then it is compressed isothermally to original volume. The specified amount of heat is measured at 1304J. Determine C_p / C_v, and specify the type of ideal gas were' talking about.

    2. Relevant equations
    So far I'v drawn a pressure/volume diagram and tried to express everything in terms of unknown p_1, unknown v_1 and known t_1. Then I'v kinda done just about anything I know in thermodynamics, but I'v got no clue in what I'm doing. I looked in the answers and just tried to manipulate my way the correct answer but so far I'm unsuccessful.
    Another thing i tried is, since C_p and C_v is expressed in partial derivatives of the temperature and the last change in the gas was isothermic, i tried to manipulate the equations from that... right now I'm completely lost.

    3. The attempt at a solution
    No idea
  2. jcsd
  3. May 9, 2012 #2

    I like Serena

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    Homework Helper

    Let's start with the relevant equations.

    Let ##γ=\frac {C_p}{C_v}##.

    In an adiabatic process ##TV^{γ-1}=constant##.
    In an isothermal process ##Q=RT\ln \frac {V_1} {V_2}##.

    You can find these equations for instance on wikipedia.

    Can you solve these equations for γ?
  4. May 11, 2012 #3
    I got it now, thanks. My problem were how to express c_v and c_p.
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