1. Limited time only! Sign up for a free 30min personal 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!

Homework Help: 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


    User Avatar
    Homework Helper

    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.

  4. Dec 16, 2012 #3


    User Avatar
    Homework Helper
    Gold Member
    2017 Award

    (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.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook