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Homework Help: Calculate the work done in polyatomic gas

  1. Jul 18, 2011 #1
    1. The problem statement, all variables and given/known data
    Calculate the work done by the system in an irreversible (single step) adiabatic expansion of 2 moles of a polyatomic gas ([itex]\gamma[/itex] = 4/3) from 300K and pressure 10 atm to 1 atm.

    2. Relevant equations
    Work done in adiabatic process
    W = nCv[itex]\Delta[/itex]T
    n = Moles of gas
    Cv = R/([itex]\gamma[/itex]-1) R-Universal gas constant
    [itex]\Delta[/itex]T- Change in absolute temperature

    3. The attempt at a solution
    The given answer is 405R. I am unable to find out the change in temperature as final temperature and volume are unknown. Is there any other formula to calculate the work done in adiabatic expansion?
  2. jcsd
  3. Jul 18, 2011 #2
    Are you aware that [itex]P V^{\gamma} = constant[/itex] for adiabatic processes? You can find the final temperature using this fact and the ideal gas equation of state.
  4. Jul 22, 2011 #3
    I think PV[itex]\gamma[/itex]= constant is applicable for adiabatic reversible processes only. It is irreversible process..
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