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Homework Help: Adiabatic/Isothermal process

  1. Feb 15, 2007 #1
    Hi people!
    So i have a homework question that i am stuck on!!

    Four moles of an ideal monatomic gas undergoes an adiabatic expansion from intial volume of 1m cubed and a temperature of 300k to a final volume of 10m cubed. a) How much wrk is done by the gas ? b) what is the final temperature? c) If instead the gas expands isothermally to 10m cubed, how much work is done? d) In part C where does the energy come from to perform the work? ...thats a lot!

    I thought of using the equation of work W(by)= 1/(1-gamma) x (PfVf-PiVi) to fnd the answer for a...but I don't have the pressure..:rolleyes: then i thought that maybe I could use deltaE= Q(in) - W (by)...but I don't know the change in temperature, therefore; im all over the place and I don't know where to start.. any hints/help would be appreciated! Thanks
  2. jcsd
  3. Feb 15, 2007 #2


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    With the information you were given, you can find the initial pressure of the gas.
  4. Feb 15, 2007 #3

    Andrew Mason

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    First work out the initial pressure, which is easy since you are given n,Ti and Vi.
    What is the relationship between P and V in an adiabatic expansion/compression? (hint: it involves [itex]\gamma[/itex]). That will give you the final pressure and, if you know n, Vf and Pf you can determine Tf.

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