Why standard entropy of an elementary substance is not zero whereas standard enthalpy of formation is taken as zero?

Explanation

To understand why the standard entropy of an elementary substance is not zero while the standard enthalpy of formation is taken as zero, we can break down the concepts of entropy and enthalpy step by step.

### Step-by-Step Solution:

1. **Understanding Standard Entropy**:
- Entropy is a measure of the randomness or disorder of a system. It quantifies the number of ways a system can be arranged while still having the same energy.
- For any substance, including elementary substances, there is always some degree of molecular motion and randomness present, even at standard conditions (298 K and 1 atm). This means that the entropy of an elementary substance cannot be zero.

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