1. Not finding help here? Sign up for a free 30min 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!

Internal Energy of an ideal gas

  1. May 18, 2008 #1

    TFM

    User Avatar

    [SOLVED] Internal Energy of an ideal gas

    1. The problem statement, all variables and given/known data

    The temperature of 0.158 mol of an ideal gas is held constant at 67.0 degrees Celsius while its volume is reduced to a fraction of 20.0 % of its initial volume. The initial pressure of the gas is 1.19 atm.

    What is the change in its internal energy?

    2. Relevant equations

    [tex] U = \frac{1}{2}nRT [/tex] (Per degrees of Freedom)

    3. The attempt at a solution

    I tried putting in the values to get U, but it doesn't say how many deggress of Freedom, so I triued using three (Monatomic) But this is wrong. Is there another Formula for the Internal Energy, becasue there are several similar questions, but none seem to be used with the releveant formula above?

    So any help/idea will be very greatly appreciated,

    TFM
     
  2. jcsd
  3. May 18, 2008 #2
    hmm U depends only on T, as you can see from the equation.
    And In the question, it is mentioned that T is kept constant. (n doesn't change anyway and R is a constant)

    so change in U = ??
     
  4. May 18, 2008 #3

    TFM

    User Avatar

    As there is no change intemprature, would there be no change in U, then?

    TFM
     
  5. May 18, 2008 #4
    Yes, if I'm not missing something.

    This is valid for ideal gases only, though.
     
  6. May 18, 2008 #5

    TFM

    User Avatar

    I just put 0 into MasteringPhysics, and it is the right answer. Thanksm, Raze2Dust! :smile:

    Technically, the should the formula actually be:

    [tex] U = \frac{1}{2}nR\Delta T [/tex] per degree of Freedom?

    Thanks,

    TFM
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?