• Support PF! Buy your school textbooks, materials and every day products Here!

Vibrational entropy and the partition function

  • #1
89
1

Homework Statement


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.

Homework Equations



[/B]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

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.
 

Answers and Replies

  • #2
232
20
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.
 

Related Threads on Vibrational entropy and the partition function

Replies
0
Views
1K
  • Last Post
Replies
1
Views
4K
  • Last Post
Replies
0
Views
2K
  • Last Post
Replies
2
Views
1K
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
3
Views
9K
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
1
Views
825
  • Last Post
Replies
0
Views
942
Top