Consider a process in which the entropy of a system increases by 125 J K-1 and the entropy of the surroundings decreases by 125 J K-1. Is the process spontaneous?

Answer : The process is not spontaneous.

Explanation:

As, we know that:

Change in entropy = Change in entropy of system + Change in entropy of surrounding

As we are given in question, the entropy of surroundings decrease by the same amount as the entropy of the system increases.

For the given reaction to be spontaneous, the total change in entropy should be positive.

Given:

Entropy change of system = + 125J/K

Entropy change of surroundings = - 125J/K

Total change in entropy = Entropy change of system + Entropy change of surroundings

Total change in entropy = 125 J/K + (-125 J/K)

Total change in entropy = 0

The process is at equilibrium because the entropy change is equal to zero. So, the process is not spontaneous.