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Question on expansion and Compression of gas?

  1. Jan 31, 2013 #1
    1. The problem statement, all variables and given/known data

    If a pressure of gas is suddenly reduced and we let the gas to expand again until it reaches equilibrium. What is final volume, work done and heat in this process? and what would be change in internal energy?
    Again the pressure is suddenly increased back to initial pressure and gas is compressed to initial volume. What would be work done heat and change in internal energy?
    Temperature is same throughout all process

    2. Relevant equations

    PV=nRT
    ΔU=q+w
    w=p*ΔV

    3. The attempt at a solution

    Here All the process is done at isothermal condition so Boyles law apply
    P1V1=P2V2

    where V2 is volume after the gas comes to equilibrium, so,
    V2=P1V1/P2

    since the process is carried in isothermal condition
    ΔU=0

    w=p*ΔV

    0=q+p*ΔV -------> q=-p*ΔV

    Now when the pressure is increased back to initial condition

    ΔU=0 ( since process is still isothermal)
    ΔU=q+p*ΔV ---------> q=-p*ΔV, here change in volume is volume after decreasing pressure - initial volume

    I am not sure if I am correct or not? Help
     
  2. jcsd
  3. Jan 31, 2013 #2
    Can anyone help me with this problem?
     
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