Will the entropy change be equal if a state change is brought about reversibly and irreversibly?

Since entropy is a state function so it doesn't depends on the path followed. So will the entropy change be equal if a state change be first brought about reversibly and then irreversibly.

• The Q/A model of StackExchange network does mean the question title is the question and the question body is the answer. The title is to be a summary question or word expression and the body is expected to contain the full question elaboration. But it is not really a question if you already knew an answer, so why it was posted ? Commented Oct 24, 2020 at 13:56
• In my text book it was mentioned that in irreversible process the entropy change of system+the entropy change of surroundings taken together is greater than zero and in reversible process it is equal to zero, so i was getting a bit confused. That's why I asked if the entropy change would be same Or not. Can you explain the above point to me that why in irreversible process it happens so? Commented Oct 25, 2020 at 15:55

3 Answers

If the initial and final states of systems are the same for both reversible and irreversible process, the entropy change for the systems will be the same.

But the entropy change for the surrounding will not be the same, as the final states will be different. The surrounding for the irreversible process will end with higher entropy.

Therefore the total entropy change is zero for reversible processes, but positive for irreversible ones.

The irreversibility condition applies not only to system-surrounding interactions, but for system internal processes as well.

Yes, that is how we determine the entropy change of a system for an irreversible process . We determine the entropy change for a reversible path between the same two end states.

Yes, they will be the same. As you know, entropy is a state function and it only depends on the initial and final states. Whether the process is reversible or not does not affect the entropy change (i.e. the entropy change does not care about the path).