Question

Diff. between entropy of ISOLATED system and Entropy of Adiabatic Process?​

Answer 1

5.6 Muddiest Points on Chapter 5

MP 5..1 Why is always true?

This is a relation between state variables. As such it is not path dependent, only depends on the initial and final states, and thus must hold no matter how we transition from initial state to final state. What is not always true, and what holds only for reversible processes, are the relations and . One example of this is the free expansion where , but where the quantities and (and the integrals of these quantities) are not zero.

Answer 2

So, in a reversible adiabatic process as Qrev = 0, the change in entropy is zero. Where as for a irreversible process it wouldn't be zero due to entropy generation.

Entropy is constant in reversible adiabatic process and it increases in irreversible adiabatic process

The entropy of an isolated system during a process always increases, or in the limiting case of a reversible process remains constant (it never decreases).

This is known as the increase of entropy principle.

The entropy change of a system or its surroundings can be negative; but entropy generation cannot.