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Hydrogen gas liquid equation

  1. Mar 22, 2005 #1
    If 277 L of LIQUID hydrogen has a mass of 19.7 kg, what volume will this amount of hydrogen occupy as a GAS at 25 degrees celcius and 1 atm?

    Is there some kind of equation that I can use to make this problem easier?

  2. jcsd
  3. Mar 22, 2005 #2
    PV = nRT

    You'll use this equation for almost every gas problem.

    R (ideal-gas constant) = 0.0821 L-atm/mole-K
    V = volume (L)
    P = pressure (atm)
    n = amount (moles)
    T = temperature (K)

    V = nRT/P

    You need to convert the 19.7 kg H2 to moles H2 and the 25 C to Kelvin.

    If you need more help, go ahead and ask.
  4. Mar 22, 2005 #3
    Do you have to take into account the hydrogen beginning as a LIQUID and ending as a GAS?
  5. Mar 22, 2005 #4
    No because when you go from a liquid to a gas, the number of moles of H2 will still stay the same and therefore you can predict the volume.
  6. Mar 22, 2005 #5
    When converting 19.7 Kg to moles would you use H2 (being 2.0158g) or just H (being 1.0079g)?
  7. Mar 22, 2005 #6
    Good question. Always use the diatomic molecule...so H2.
  8. Mar 22, 2005 #7
    Thanks for your help. So if i have done things right my answer should be close to 2.39 X 10^5 L :smile:
  9. Mar 22, 2005 #8
    Yes I got a similiar answer. By the way, what value are you using for R? 0.0821 or something more precise?
  10. Mar 22, 2005 #9
    For this problem I just used 0.0821, but usually I use 0.082057
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