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Isothermal expansion

  1. Apr 16, 2007 #1
    55 moles of an ideal gas, at an initial pressure of 3.00 × 105 N/m2 and an initial volume of 1.700 m3, undergo a small isothermal expansion to a volume of 1.720 m3. Find the work done by the gas.


    i am confused about the units but here is what i got...

    so w=nRTln(vi/vf)


    so i know n and i know vi and vf......now for R i think i am going to use 8.314 J/mol K....are those the right units?


    so to find T i must use PiVi=nRT

    but what units does P and V have to be in to yeild K and shoud use the same units for R as i wrote above?
     
  2. jcsd
  3. Apr 16, 2007 #2

    Chi Meson

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    You are using the correct formula and the correct reasoning. The constant R (8.314 N*m/mol*K) is designed specifically to give you the right units. You will get the temperature in Kelvins.

    P*V, by the way, gives you a unit equivalent to joules. Pressure can be considered to be a measurement of energy per volume ratio. In a monatomic ideal gas, the internal energy of the gas is equal to (3/2)PV.
     
  4. Apr 16, 2007 #3
    thank you so much
     
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