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Homework Help: Thermal Equalibrium

  1. Jan 21, 2009 #1
    1. The problem statement, all variables and given/known data

    A sealed, evacuated 3.11 liter container initially contains 0.87 liter of liquid helium. As the contents of the container come into thermal equilibrium with the surroundings, the liquid helium vaporizes and turns into gas. If the temperature of the laboratory is 24.8°C, what is the pressure of the helium gas inside the container? (Note: The density of liquid helium is 122.1 kg/m3.)

    2. Relevant equations

    Truthfully I dont have any idea on how to set this up. Any help at all would be thankful.
    3. The attempt at a solution
  2. jcsd
  3. Jan 22, 2009 #2


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    Homework Helper

    Figure first the mass of the helium in the container.

    The total mass divided by the atomic mass will tell you how many moles of helium atoms you have inside.

    At that point it's

    PV = nRT isn't it?

    You know T, you know V and you know n moles so ...
  4. Jan 22, 2009 #3
    Yep that was it all along i was just missing a step and using the wrong constant. Thanks
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