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Dec18-12, 02:14 AM
P: 5,462
I mean, if I have a container of gas at some temperature above 0 K, then I can extract all of its internal energy as work, just let it quasistatically expand to infinity.
Such a container has internal pressure P.

Expanding from P into a vacuum does no work.
Expanding from P against an external pressure P' < P does work, but as this happens P diminishes until P = P' when the system is in equilibrium.

How would you proceed from this equilibrium to infinity, where P = 0 ?