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Homework Help: Internal Energy of argon

  1. Apr 23, 2013 #1
    1. The problem statement, all variables and given/known data
    Argon is a monatomic gas for which all the internal energy of the molecules may be considered to
    be translational kinetic energy.
    Molar mass of argon = 4.0 x 10-2
    The Boltzmann constant = 1.38 x 10-23 J kg-1
    The Avogadro constant = 6.02 x 1023 mol-1
    Calculate the internal energy of 8.0 g of argon gas at a temperature of 100 K.

    2. Relevant equations

    pV=nRT or pV=NKT


    3. The attempt at a solution
    So far I'm assuming you need U=3/2NKT

    We know that 1 mol = 4x10^-2 Kg

    So i did 0.008/4x10^2 = 0.2

    0.2 x Avagardo's Constant = 1.204x10^23

    And subbed that into U=3/2NKT as N

    The final answer I got was as U was 248.4J

    To be honest i have no clue what I did as its been so long since I've done Physics.

    Thanks for any help or any pointers in the right direction.
  2. jcsd
  3. Apr 23, 2013 #2


    User Avatar

    Staff: Mentor

    That looks correct. By the way, since you calculated the amount of argon in moles, you could've used U=3/2nRT instead of calculating N, but the result is the same.
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