Vibrational entropy and the partition function

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SUMMARY

The discussion focuses on calculating the molar entropy of oxygen gas at 298.15 K and 1 bar using the vibrational entropy formula. Key parameters include a molecular mass of 5.312×10-26 kg, vibrational temperature (Θvib) of 2256 K, rotational temperature (Θrot) of 2.07 K, and the symmetry number (σ) of 2. The entropy equation utilized is S = NkT ∂/∂T {ln q} + Nk ln (q/N) + Nk, where qvib is defined as e-(Θvib/2T)/(1 - e-(Θvib/T)). The user is advised to seek assistance in a more appropriate forum for thermal physics or thermodynamics.

PREREQUISITES
  • Understanding of statistical mechanics concepts, particularly the partition function.
  • Familiarity with the concepts of vibrational and rotational temperatures in thermodynamics.
  • Knowledge of entropy calculations in the context of ideal gases.
  • Proficiency in using Avogadro's number and Boltzmann's constant in calculations.
NEXT STEPS
  • Research the derivation and application of the vibrational partition function in thermodynamics.
  • Learn about the calculation of molar entropy for different gases using statistical mechanics.
  • Explore the relationship between temperature and entropy in ideal gases.
  • Investigate common mistakes in entropy calculations and how to avoid them.
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This discussion is beneficial for students and professionals in the fields of thermal physics, physical chemistry, and anyone involved in calculating thermodynamic properties of gases.

jbowers9
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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 Boltzmann'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.
 
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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.
 

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