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Isobaric Process, finding Change in Internal Energy

  1. Dec 16, 2012 #1
    1. The problem statement, all variables and given/known data

    Assume nitrogen gas (N2) is an ideal gas. n = 7.57 moles of N2 gas are heated isobarically (at constant pressure) from temperature To = 18.6 oC to temperature Tf = 50.9 oC. Find:

    c) ΔIE, the change in internal energy of the N2 gas

    2. Relevant equations

    Change in IE = Change in KE = (3/2)nRΔT

    3. The attempt at a solution

    Since this is an ideal gas, only Kinetic Energy considerations need to be accounted for, or,
    Change in KE = Change in IE = (3/2)(7.57)(8.314)(50.9-18.6) = 3,049.29 Joules

    Once again, thanks for the help! I think I am doing the correct thing, or am I going crazy? =)
     
  2. jcsd
  3. Dec 16, 2012 #2

    ehild

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    The internal energy of the two-atomic ideal gas contains not only the translational KE, but also the energy connected to rotation. Generally, the internal energy of ideal gases is f/2 nRT where f is the degrees of freedom, 5 for a two-atomic molecule.

    ehild
     
  4. Dec 16, 2012 #3

    TSny

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    (3/2)nRΔT accounts for only the change in translational KE of the molecules. N2 is not a monatomic gas, so the molecules can have additional motion besides translational motion.
     
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