irreversible expansion of ideal gas

Boltzmann Equation for Entropy: $S = k_{B} \ln W$

Payton Kammerer 2B
Posts: 49
Joined: Tue May 01, 2018 3:00 am

irreversible expansion of ideal gas

Why is w=0 for this? the example on p. 326 uses this to show that the entropy change of the surroundings is 0, which doesn't make a lot of sense to me on a conceptual level.

Frank He 4G
Posts: 50
Joined: Tue Nov 12, 2019 12:19 am

Re: irreversible expansion of ideal gas

Looking at the example, it says free expansion. When something is said to freely expand, it means that the external pressure is 0. That means that w = -PV = 0.

Elizabeth Harty 1A
Posts: 125
Joined: Sat Jul 20, 2019 12:16 am

Re: irreversible expansion of ideal gas

Is W always zero for irreversible expansion?

Tauhid Islam- 1H
Posts: 64
Joined: Fri Aug 02, 2019 12:15 am

Re: irreversible expansion of ideal gas

From my understanding, free expansion is the same as a irreversible expansion which is when there is no external pressure on the system. If the system has no external pressure and if the gas is expanding against no external pressure, the gas is said to expand freely. Because there is no expansion against an external pressure, the expanding gas does no work, because work is equal to FD which is external force times distance traveled. No external force no work.

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