The importance of reversible processes(?)

[ShayanJ]

In thermodynamics(at least in classical thermodynamics),the idealization of reversible processes is used time and again.Can we say it is central to thermodynamics?
I mean can we say it is so important that if we can't find a reversible counterpart for an irreversible process,then the existence of that process is in contradiction with thermodynamics?If yes,can we just drop the notion of reversible process in favor of the existence of one having no reversible counterpart?
Thanks

 

[Andrew Mason]

In thermodynamics(at least in classical thermodynamics),the idealization of reversible processes is used time and again.Can we say it is central to thermodynamics?
I mean can we say it is so important that if we can't find a reversible counterpart for an irreversible process,then the existence of that process is in contradiction with thermodynamics?If yes,can we just drop the notion of reversible process in favor of the existence of one having no reversible counterpart?
Thanks

There is always a reversible process between any two thermodynamic states.

Reversible paths are useful because the system remains in equilibrium during the entire process. So one can define state functions using reversible paths. For example, we can define a quantity called entropy such that the change in entropy between two states is the integral of dQ divided by T over a reversible path between those two states. We can show that entropy is a state function so it does not depend on the path taken in getting from the initial to the final state. But it is defined in terms of the reversible path between those two states.

AM