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Homework Help: Equipartition of Energy/Thermodynamics

  1. Nov 12, 2008 #1
    1. The problem statement, all variables and given/known data
    Consider 2 mol of an ideal diatomic gas (a) Find the total heat capacity as defined by Q = C[tex]\Delta[/tex]T at constant volume and the total heat capacity at constant pressure, assuming the molecules rotate but do not vibrate.
    (b) Repeat part a, assuming the molecules BOTH rotate and vibrate

    2. Relevant equations

    Q = C[tex]\Delta[/tex]T
    Cv = 5R/2 (constant volume)
    Cp = 7R/2 (constant pressure)

    3. The attempt at a solution
    I'm not really sure what to do here. I THOUGHT that the answer would be 5R/2 for constant volume and 7R/2 for constant pressure, but I'm not sure what they mean by "as defined by Q = C[tex]\Delta[/tex]T." Also, that leaves my n value unused, and it's way too simple an answer.

    I was trolling the textbook and found this:
    Eint = 3N(1/2kbT) + 2N(1/2kbT) = 5/2nRT
    That's for a diatomic gas whose molecules have 5 degrees of freedom: 3 translational, 2 rotational.
    But I'm not really sure how that helps me at all.
  2. jcsd
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