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Homework Help: Using the ideal gas law with two unknowns

  1. May 9, 2013 #1
    1. The problem statement, all variables and given/known data

    You are given a closed container containing a single atom ideal gas.
    The volume is V1= 0,45*10^(-3) m^3
    Pressure p1 is 3,2 MPa
    Temperature, T1, is 892 K

    The volume of the gas is increased to V2= 8*V1

    Find the pressure and temperature after the increase of volume.

    2. Relevant equations

    Ideal gas equation pV=nRT

    3. The attempt at a solution

    I have n= 0,19 moles from a previous question. R is the ideal gas constant, 8,31 J/moles*K

    Manipulating the ideal gas equation for pressure gives me p = (nRT)/V but that leaves T as an unknown so I'm not sure if that's the right way to go...
  2. jcsd
  3. May 9, 2013 #2


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    Staff: Mentor

    I would expect that the expansion is adiabatic, this gives another constraint on the gas.
  4. May 10, 2013 #3
    I was looking at that and tried to find the new temperature by using T2= T1*([itex]\frac{V1}{V2}[/itex])[itex]\gamma-1[/itex] which gave me 221,46K which is not correct according to my lecturer.
  5. May 10, 2013 #4


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    Staff: Mentor

    It would be interesting to see how the lecturer would solve this.
  6. May 27, 2013 #5
    I get 223 K. What does your lecturer think about that answer?
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