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Adiabatic expansion of a gas

  1. Dec 9, 2015 #1
    1. The problem statement, all variables and given/known data
    A gas consisting of diatomic molecules that can rotate but not oscillate at a given range of temperatures expands adiabatically from pressure of 365Pa and volume of 70m3, doing 101J of work, while expanding to a final volume. What is its final PV (pressure volume) product?

    2. Relevant equations
    For an adiabatic expansion:
    W = (1/ϒ-1)(pfvf - pivi)

    3. The attempt at a solution
    i) Degrees of freedom: 3
    Therefore, ϒ=1.4

    ii) Plug and chug of the equation above.
    W = (1/ϒ-1)(pfvf - pivi)
    101 = (1/1.4-1)(pfvf - 365*70)
    101 = 2.5pfvf - 63875
    pfvf = 25590 Pa / m3

    I'm fairly certain I found the degrees of freedom correctly, and the latter part of my calculations is pretty straightforward... Still getting the wrong answer, however. Chance that the answer is wrong? Or am I approaching the problem incorrectly?
  2. jcsd
  3. Dec 9, 2015 #2


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    Isn't it 3 degrees of freedom for a monatomic gas?
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