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Homework Help: Monatomic and diatomic mix

  1. May 31, 2007 #1
    n_1 moles of a monatomic gas and n_2 moles of a diatomic gas are mixed together in a container.
    Derive an expression for the molar specific heat at constant volume of the mixture.

    c sub v = 3/2 R for a monatomic gas
    5/2 R for a diatomic gas

    thermal energy for a monatomic gas = 3/2 NkT = 3/2 nRT
    diatomic Eth = 5/2 NkT = 5/2 nRT

    c = J/molK, R = J/molK, n = mol

    I started off by looking at the units and figuring that I needed to divide the n's somehow and multiply that times R...but I have tried many equations and can't seem to find one that works, and I can't figure out logically how that would work out...does anyone have any ideas?? I'm desperate
  2. jcsd
  3. May 31, 2007 #2


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    If the temperature of the mixture is to be raised by dT the heat required (at constant volume) will be

    n1(3R/2)*dT + n2(5R/2)*dT

    Now what is the definition of molar specific heat?
  4. May 31, 2007 #3
    I figured it out, thank you!
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