Gibbs equation and third law of thermodynamics

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SUMMARY

The discussion centers on the Gibbs equation and its application to irreversible adiabatic processes involving ideal gases, particularly as they approach absolute zero (0 K). The entropy change is expressed as Δs=Cv ln(T2/T1)+R ln(V2/V1), highlighting the impossibility of reaching 0 K, which supports the third law of thermodynamics. Participants question the validity of applying the Gibbs equation to irreversible processes, noting that heat exchange does not equal Tds in such scenarios. The conversation also touches on the kinetic energy of molecules in ideal gases compared to gravitational potential energy.

PREREQUISITES
  • Understanding of the Gibbs equation and its components
  • Familiarity with the third law of thermodynamics
  • Knowledge of entropy and its calculation for ideal gases
  • Concepts of irreversible processes in thermodynamics
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  • Study the implications of the third law of thermodynamics on entropy
  • Explore the derivation and applications of the Gibbs equation
  • Investigate the behavior of ideal gases during irreversible adiabatic expansion
  • Learn about the relationship between kinetic energy and potential energy in thermodynamic systems
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Students and professionals in thermodynamics, physicists, and engineers interested in the behavior of gases under extreme conditions and the principles governing entropy and energy transformations.

kelvin490
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I have seen a discussion of what would happen for an ideal gas expands irreversibly and adiabatically until absolute zero degree K. The entropy change is like that:

Δs=Cv ln(T2/T1)+R ln(V2/V1)

It is impossible for T2 to be zero K in the equation and so it becomes one justification of the third law. I wonder whether it is valid and whether an irreversible process can be represented by the above equation. For irreversible process the heat exchange is not equal to Tds so can the Gibbs equation be applied?
 
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kelvin490 said:
I have seen a discussion of what would happen for an ideal gas expands irreversibly and adiabatically until absolute zero degree K.

This begs the question of whether an average molecule in this ideal gas has more kinetic energy than gravitational potential energy.
 

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