Spontaneous Expansion of Gas into Evacuated Container: Thermodynamic Analysis

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Discussion Overview

The discussion revolves around the thermodynamic analysis of a gas spontaneously expanding into an evacuated container. Participants explore the implications for various thermodynamic variables such as delta T, delta E, delta H, delta S, q, w, and delta G, considering whether they are positive, negative, or zero. The scope includes theoretical reasoning and homework-related inquiries.

Discussion Character

  • Homework-related
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that delta T is zero, assuming the process is isothermal, but questions whether this assumption is valid.
  • Another participant challenges the assumption of isothermal conditions and asks for reasoning behind delta H being negative.
  • Some participants propose that if the gas is ideal, delta E would be zero, and they consider the implications for assuming an isothermal reaction.
  • There is a suggestion that delta H might be positive because added heat is needed for the gas to expand.
  • One participant defines enthalpy as the sum of internal energy and PV, questioning whether delta H could be zero.

Areas of Agreement / Disagreement

Participants express differing views on whether the process can be considered isothermal and the signs of delta H and delta E. The discussion remains unresolved, with multiple competing perspectives on these thermodynamic variables.

Contextual Notes

Assumptions about ideal gas behavior and the definition of enthalpy are not fully explored, and the implications of the gas expanding into an evacuated container are not clearly defined.

coookiemonste
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Homework Statement


A gas spontaneously expands into an evacuated container. Indicate whether delta T, delta E, delta H, delta S, q, w, and delta G are positive, negative, or zero.


Homework Equations


delta G < 0 (spontaneous)
delta G= delta H - TdeltaS
delta E= q + w
[/B]

The Attempt at a Solution


delta T: 0? (Is it wrong to assume this is an isothermal reaction?)
delta E: 0
delta H: -
delta S: +
q: 0
w: 0
delta G: -
Am I correct? And what difference does it make that it is in an evacuated container?
 
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It's not the best approach to assume this is an isothermal process. Can you show that's it's an isothermal process, by assuming ideality and using what you know about the change in energy?

What's your reasoning behind delta H being negative?
 
Hmm. If the gas is considered ideal, delta E would be zero. Since the internal E depends on T, we can assume that this is an isothermal reaction?

Should delta H be + because added heat is needed to make the gas expand?
 
coookiemonste said:
Hmm. If the gas is considered ideal, delta E would be zero. Since the internal E depends on T, we can assume that this is an isothermal reaction?

Agreed.

coookiemonste said:
Should delta H be + because added heat is needed to make the gas expand?

How is enthalpy defined?
 
Enthalpy is equal to the internal Energy + PV. So is delta H=0?
 
Yep.
 
thank you!
 

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