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Internal Enery, heat and work/HELP

  1. Mar 4, 2010 #1
    1. The problem statement, all variables and given/known data
    There's .1 mole of an ideal gas trapped in a cylinder with a movable piston.
    If Pi= Pf= 5000Pa, Vi= .04 m^3, Vf= .08m^3, Q=500J,,,Find W, change in (U), Ti and Tf.

    2. Relevant equations

    change in U = Q+W
    W= -p change in V

    3. The attempt at a solution

    W= 200J
    change in U = 700J
    Ti=
    Tf= i don't know how to get Ti and Tf... I am not sure whether 200J and 700J are right either..
    PLease help me!!
    Thank you!
     
  2. jcsd
  3. Mar 5, 2010 #2

    ehild

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    Homework Helper
    Gold Member

    You certainly know an equation connecting P, V and T for an ideal gas.

    The gas expands, is the work done on the gas positive or negative? Will this work increase or decrase the internal energy?

    ehild
     
  4. Mar 5, 2010 #3
    PV=nRT

    Could you please explain more in detail? I don't get what you're saying:(

    THanks.
     
  5. Mar 5, 2010 #4

    ehild

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    Gold Member

    You know P, V, n for both states of the gas, don't you? Can you calculate the temperatures?

    ehild
     
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