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Work of isothermal compression at constant pressure

  1. Sep 26, 2015 #1
    The Problem:

    A 1.80 mol sample of an ideal gas is compressed isothermally from 58.1 L to 15.6 L using a constant external pressure of 2.72 atm .

    Calculate W:

    Calculate Q:

    Calculate ΔU:

    Attempt at solution:

    I tried W = P(ΔV) to no effect, W = nRTln[Vf/Vi] to no effect. The online submission form tells me if the sign is wrong so I know that the numbers I got from these two equations are not correct as if they were and the sign was wrong it would have told me. I used 273K as T since T is not given.

    Any help would be appreciated. Due at midnight and friends have all remained oddly out of contact.

    I can't go for Q and U until I figure out the first part.


  2. jcsd
  3. Sep 26, 2015 #2
    Well, if the external force per unit area is held constant at 2.72 atm, the work should be PΔV = -115.6 liter-atm. What units do they want the answer in?

    If the initial and final temperatures of an ideal gas are the same (isothermal), what is ΔU?

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