Joule's Expansion & Entropy Production

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Discussion Overview

The discussion revolves around Joule's expansion of gases, specifically focusing on the conditions of free expansion under adiabatic and isothermal scenarios, and the implications for entropy production. Participants explore the thermodynamic principles involved, particularly the first law of thermodynamics and the concept of entropy in relation to energy availability.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • One participant states that in free expansion of gases under adiabatic conditions, no work is done and the internal energy remains constant, yet entropy increases, raising the question of the source of the associated unavailable energy.
  • Another participant questions the possibility of maintaining isothermal conditions during free expansion, suggesting that thermal isolation only supports adiabatic conditions.
  • A later reply affirms that Joule-Thomson effect does not occur isothermally, indicating a distinction between the two processes.
  • Further clarification is provided that the process being discussed is indeed free expansion of an ideal gas, which maintains temperature due to perfect thermal isolation.
  • Another participant argues that for the gas to expand while maintaining its temperature, heat energy must be supplied, implying that the process cannot be isothermal.

Areas of Agreement / Disagreement

Participants express disagreement regarding the feasibility of isothermal conditions during free expansion, with some asserting that it is not possible while others maintain that it can occur under specific conditions. The discussion remains unresolved with competing views on the nature of the expansion process.

Contextual Notes

There are limitations regarding the assumptions made about thermal isolation and the definitions of adiabatic versus isothermal processes. The discussion does not resolve the mathematical implications of entropy changes in the context of Joule's expansion.

hyperickz
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We all know that in free expansion of gases under adiabatic condition and keeping the temperture constant ,we get that no work is done by the gas.Moreover since del(Q)=0, del(U)=0 according to first law of thermodynamics.But we get a increase of entropy by an amount Rln2.Now the question is that from where does the unavailable energy associated with entropy i.e. Tdel(S)=RTln 2 comes from ?
 
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hyperickz said:
We all know that in free expansion of gases under adiabatic condition and keeping the temperture constant
Is this possible?
 
joule thompson effect does not take place isothermally.
 
Its not joule thomson effect.Its free expansion of ideal gas during which temperature remains same due to perfect thermal isolation
 
thermal isolation provides only adiabatic conditions not isothermal, for the gas to expand and still maintain its temperature you'll have to supply heat energy.
bottom line, the process you are referring to cannot be isothermal.
 

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