1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Thermal Physics

  1. Nov 13, 2008 #1
    1. The problem statement, all variables and given/known data
    A steel container contains 300g of ideal gas at a pressure of 1.35 x 106 Pa and temperature of 77oC. When the tank is checked later, the temperature is dropped to 22oC and the pressure has fallen to 8.7 x 105 Pa. How many grams of gas leaked out of the tank?

    2. Relevant equations
    PV = NkT

    3. The attempt at a solution
    first, converting: 77oC = 350.15K and 22oC = 295.15K

    The problem is, i do not know how to link mass to the equation of PV = NkT
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Nov 13, 2008 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Hint: Can you relate N - the number of particles to the mass?
  4. Nov 14, 2008 #3
    Number of particles = Total mass / mass per molecule?

    But i do not know the mass per molecule...
  5. Nov 14, 2008 #4
    I really need an answer quick, my holidays are ending soon and this is my holiday assignment question that i only stuck with..
  6. Nov 14, 2008 #5
    HINT 2 : Avogardro number.......
  7. Nov 15, 2008 #6
    I tried it again, closest i could get was,

    PV = nRT

    n = Mtotal / Mpermole = Mtotal/(mNA)

    Where m = mass per molecule..
  8. Nov 15, 2008 #7

    Assume that each particle have the mass [tex]m_0[/tex]. Can you now relate the mass to the number of particles N?
    Use this relations to express N in terms of m. Now you can relate the mass after [tex]m_2[/tex] to the mass before [tex]m_1[/tex] and this relation is independent of [tex]m_0[/tex] and only depends on known parameters.
    Hopefully this can help you to solve the problem.
  9. Nov 15, 2008 #8
    Ok i solved it!!! :D:D The crux of this problem is that, the volume before and after do not change, and i managed to equate mass/molecule.

    PV = NkT, PV = (Mtotal/mo)kT

    After the reaction,

    P'V' = N'kT', P'V' = (M'total/mo)kT

    equating mo = mo,

    I get

    MtotalT/V = M'totalT'/V'

    So i solved for M', giving 229.36 g. So, the mass that leaked = (300 - 229.3) g = 70.6g

    I forgot that V was constant, that was perplexing me throughout!!
  10. Nov 15, 2008 #9


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Good job :approve:
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Thermal Physics
  1. Thermal Copper Physics (Replies: 1)

  2. Thermal Physics (Replies: 1)

  3. Thermal Physics (Replies: 1)

  4. Thermal Physics (Replies: 8)