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Homework Help: Pressure + volume

  1. May 26, 2010 #1
    1. The problem statement, all variables and given/known data

    A 12 litre gas bottle is initially charged with air to 232 BAR at 30 C. What will be the new pressure in the bottle once it has cooled to 8 C?

    A diver breathes from the gas bottle above, is working at a depth of 40m, and at a temperature of 8 C.

    If the diver exhales a bubble of air with a volume of 0.5 litres, what will the volume of the bubble be when it reaches the surface?

    2. Relevant equations

    not sure...

    3. The attempt at a solution

    I know for the first part that using the combined gas law

    (P1/T1) x T2 = 215 BAR

    P = pressure
    T = temperature in kelvin

    However i'm stuck on where to go with the next part.

    Any pointers/hints in the right direction would be really appreciated. thanks
  2. jcsd
  3. May 26, 2010 #2
    Since you know the diver's depth you can determine the pressure at that depth. You are also given the temperature and volume of the air bubble at that depth. As the bubble rises it will expand to a larger volume. You will need to determine a pressure and temperature at the surface to find the new volume.
  4. May 27, 2010 #3
    Have ended up with the volume of the bubble at surface = 2.2L

    anyone think this is correct?
  5. May 27, 2010 #4


    User Avatar

    Staff: Mentor

    Not me.

    What is a pressure at 40 meters? What is a pressure at the surface?
  6. May 27, 2010 #5
    Pressure at 40m = 1000(p) x 9.81(g) x 40(h) + Atmospheric pressure (100'000) = 492800

    Pressure at surface = 100'000 Pa

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