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Homework Help: Internal Energy of helium

  1. Nov 1, 2005 #1
    A tank of volume 0.413 m3 contains 2.79 mol
    of helium gas at 5C. Assume that the helium
    behaves like as an ideal gas.
    The universal gas constant is
    8.31451 J/Kmol, and Boltzmann's constant
    is 1.38066 x10^-23 J/K.
    Find the total thermal energy of the system.
    Answer in units of J.
    Would the right equation be Eint = 3/2NKbT =3/2nRT ?
  2. jcsd
  3. Nov 1, 2005 #2

    Chi Meson

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    Science Advisor
    Homework Helper

    Both are the same. The first (with "Boltzman" constant) is for use when observing idividual atoms or molecules. N=number of molecules.

    The second is for use when observing large quantities. n = number of moles. The only difference between R and k is Avogadro's number (k = R/N)

    So, what are you given. number of molecules, or number of moles?

    Oh yeah, what's the temperature? Are you ABSOLUTELY sure?
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