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Ideal gases physics help here?

  1. Nov 21, 2012 #1
    1. The problem statement, all variables and given/known data
    A moster of a gas has 4 moles and first is in the temperature 300 K and pressure 10 atmosphere.After a change of state, ∆T= -50 K and ∆V=10 liter.Find the final temperature ,volume and pressure of the gas.


    2. Relevant equations

    P*v=n*R*T

    3. The attempt at a solution
    So T2-T1=-50 <=> T2=350-50=300 K
    Now,to find V2, I thought : Find V1 first and then do V2-V1=∆V. From pv=nRT where T =300,pressure is 10 and the moles are 4. I Find that V1=997.2 here I replace V2-997.2=10 but V2 isnt the same as in my textbook..what did I do wrong
     
  2. jcsd
  3. Nov 21, 2012 #2

    haruspex

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    Where did the 350 come from?
    Seems too much. Please post the details of that calculation.
     
  4. Nov 21, 2012 #3
    Sorry,I know it is T2-T1=-50 and here I find that T2=250 Kelvin.

    The details pv=nRT , V=(4*8.31*300)/10=997.2 litres..
     
  5. Nov 21, 2012 #4

    SteamKing

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    What are the units of your gas constant R?
     
  6. Nov 21, 2012 #5
    R= 8.31 J *K−1 mol−1
     
  7. Nov 21, 2012 #6
    SteamKing asked you about the units for the gas constant, because the units are wrong in your calculation of the initial volume.

    Since it's best to stick to the units given in the question, use the gas constant
    R = 0.08206 L.atm/K.mol

    When you're putting numbers into an equation, always include the units and check what they give for the final answer. You can avoid a lot of errors doing this.
     
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