For a reversible process, the change in entropy of the universe is:

For a reversible process, the change in entropy of the universe is:

Step 1: Understand what a reversible process is. A reversible process is one that can be reversed without any change in the system and surroundings.
Step 2: Know what entropy is. Entropy is a measure of disorder or randomness in a system.
Step 3: Recognize that in a reversible process, the system and its surroundings are in equilibrium. This means there is no net change in energy or disorder.
Step 4: Since the system and surroundings are in equilibrium, the total change in entropy (the sum of the entropy changes of the system and surroundings) is zero.
Step 5: Conclude that for a reversible process, the change in entropy of the universe (system + surroundings) is zero.

Entropy in Reversible Processes – In a reversible process, the total change in entropy of the universe (system plus surroundings) is zero, indicating that the system is in equilibrium with its surroundings.