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: Vibrational entropy and the partition function

  1. Jun 6, 2018 #1
    1. The problem statement, all variables and given/known data
    I'm asked to compute the molar entropy of oxygen gas @ 298.15 K & 1 bar given:
    molecular mass of 5.312×10−26 kg, Θvib = 2256 K, Θrot = 2.07 K, σ = 2, and ge1 = 3. I'm currently stuck on the vibrational entropy calculation.

    2. Relevant equations

    S = NkT ∂/∂T {ln q} + Nk ln (q/N) + Nk
    where N is Avogadro's # & k is Boltzman's constant,
    so Nk = R.
    qvib = e-(Θvib/2T)/(1 - e-(Θvib/T)) where Θvib = hν/k

    3. The attempt at a solution
    For the derivative of ln q
    I get
    ∂/∂T {ln q} = Θvib/2T^2{[1+ e-(Θvib/T)]/[1 - e-(Θvib/T)] which @ Θvib = 2256 K is(?) Θvib/2T^2,
    so for the first part of the entropy calculation I would have a contribution of
    RΘvib/2T.
    I can plug in the numbers but I just want to know if I'm headed in the correct direction with this and I will return to confirm other parts of the calculation.
     
  2. jcsd
  3. Jun 11, 2018 #2
    Thanks for the thread! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post? The more details the better.
     
  4. Jun 14, 2018 #3
    Hey! I'm sorry I can't answer your question, but you're not getting replies probably because it's in the wrong forum. This is more of a thermal physics/thermodynamics question. You should try posting it in the Introductory Physics Homework section.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted