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Homework Help: What is the volume of the gas after adiabatic compression

  1. Feb 16, 2016 #1
    1. The problem statement, all variables and given/known data
    1 liter of ideal diatomic gas (allow for rotation but not vibration) at a pressure of 1 atmosphere and a temperature of 300 K is compressed adiabatically to a pressure of 7 atm. What is the volume of the gas after compression?

    2. Relevant equations
    PV=NKT
    PV=nRT
    ##U_T##=f/2*NKT
    ##PV^gamma## where gamma=##(2+f)/f##


    3. The attempt at a solution
    I am not sure how to go about this. I tried just saying 1/7 of a liter, but that is not right. Professor gave a hint about the 5 degrees of freedom being important and not to use 6... I must have missed something... The only formula I have involving the degrees of freedom is the one for the Energy and the PV gamma. but I am not sure how to do that. I thought I would try plugging in the pressure and volume and then changing the Pressure... But I thought I couldn't . Now I am thinking I can again...
     
  2. jcsd
  3. Feb 16, 2016 #2
    That's it. I'm sorry. I got blocked because I did not know what PV^gamma was supposed to equal. Then while typing out my question, it dawned on me how stupid I was being. I can just set initial PV^gamma equal to final PV^gamma... I did that and solved for V_final and I got it. It always amazes me how I can sit stumped for hours on a problem. and I'll get it the moment I ask about it. ;)
     
  4. Feb 17, 2016 #3

    DrClaude

    User Avatar

    Staff: Mentor

    You have discovered for yourself the usefulness of the homework template :smile:
     
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