[betty boop]

deltaS = zero only in reversible processes.

But the second law of thermodynamics refers to non-reversible processes, and only to those.

[WildTurkey]

But the second law of thermodynamics refers to non-reversible processes, and only to those. Untrue, but it begs the question, that if that is your position, you must retract your previous discussion of deltaS =0.