Gibbs equation and third law of thermodynamics

In summary, the conversation discusses the consequence of an ideal gas expanding irreversibly and adiabatically until absolute zero degree K. It questions the validity of the entropy change equation, which involves temperature and volume, in relation to the third law. It also raises the issue of whether the Gibbs equation can be applied to irreversible processes. Additionally, it brings up the idea of whether molecules in an ideal gas have more kinetic energy or gravitational potential energy.
  • #1
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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  • #2
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.
 

Related to Gibbs equation and third law of thermodynamics

What is the Gibbs equation?

The Gibbs equation, also known as the Gibbs-Duhem equation, is a mathematical expression that relates the changes in enthalpy, entropy, and free energy of a system to changes in temperature, pressure, and composition. It is commonly used in thermodynamics to describe the behavior of substances and chemical reactions.

How is the Gibbs equation derived?

The Gibbs equation is derived from the fundamental equations of thermodynamics, namely the first and second laws of thermodynamics. It can also be derived from the Helmholtz energy equation and the Maxwell relations.

What is the third law of thermodynamics?

The third law of thermodynamics states that the entropy of a perfect crystal at absolute zero temperature is zero. In other words, as a system approaches absolute zero temperature, its entropy approaches a constant minimum value. This law provides a reference point for measuring the absolute entropy of a system.

How is the third law of thermodynamics related to the Gibbs equation?

The third law of thermodynamics is closely related to the Gibbs equation as it provides a reference point for the absolute entropy term in the equation. It also helps in calculating the absolute entropy of a system at any temperature, as the changes in entropy are measured relative to the absolute zero state.

What are the practical applications of the Gibbs equation and third law of thermodynamics?

The Gibbs equation and third law of thermodynamics have numerous practical applications in fields such as chemistry, physics, and engineering. They are used to predict the behavior of substances and chemical reactions, calculate the thermodynamic properties of materials, and study phase transitions in materials. They are also essential in designing and optimizing thermodynamic processes in industries such as energy production and chemical engineering.

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