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Homework Help: Isothermally Expanding Question

  1. Oct 8, 2013 #1
    1. The problem statement, all variables and given/known data
    Two moles of an ideal gas are compressed in a cylinder at a constant temperature at 338K until the original pressure is tripled. Calculate the amount of work done.

    2. Relevant equations
    PV/T = c

    3. The attempt at a solution
    I don't know how to incorporate the cylinder information into this problem.. or get anywhere at all really.
    3Pi = Pf
    does this lead to Vi = 3Vf? since PV/T = c and T doesn't change?

    W = PdV = nRdT..?
  2. jcsd
  3. Oct 8, 2013 #2


    User Avatar

    Staff: Mentor


    No, that doesn't make sense since P is not constant and T is.

    You need the formula for work as an integral over dV and use the ideal gas law to substitute for T which is constant.
  4. Oct 8, 2013 #3
    If the temperature is constant, what is the ratio of the initial volume to the final volume? Your equation for the work is correct (if you use the convention that dW is the work done on the surroundings by the system). Just substitute nRT/V for P and integrate.

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