Question

What is the criterion for spontaneity in a non-isolated system?

Answer 1

For a system which is not isolated , spontaneity criteria is

1) Total entropy of the system and surrounding altogether should increase .

2) Total enthaly exchange should be positive.

I.e total Gibbs free energy which is combination of enthaly and entropy term makes it more and more negative for a process to be thermodynamically feasible.

It's the combination of the enthaly and entropy that decides the direction of the process . Therefore both the factors should favor combinedly.

Or one of them favours , but then it should be greater than the one disfavouring the process.