एंटोपि का मात्रक है ---

Options

A. `JK^(-1) mol^(-1)`
B. `Jmol^(-1)`
C. `J^(-1)R^(-1)mol^(-1)`
D. `JR mol^(-1)`

Explanation

**Step-by-Step Solution:**

1. **Understanding Entropy**: Entropy is a measure of the randomness or disorder in a system. It is a fundamental concept in thermodynamics.

2. **Formula for Entropy**: The change in entropy (ΔS) can be calculated using the formula:
\[ \Delta S = \frac{Q_{\text{reversible}}}{T} \]
where \( Q_{\text{reversible}} \) is the heat exchanged in a reversible process and \( T \) is the absolute temperature in Kelvin.

3. **Units of Heat and Temperature**: The unit of heat (Q) is typically measured in joules (J), and the unit of temperature (T) is measured in Kelvin (K).

4. **Calculating the Unit of Entropy**: From the formula, we can derive the unit of entropy:
\[ \text{Unit of Entropy} = \frac{\text{Unit of Heat}}{\text{Unit of Temperature}} = \frac{\text{J}}{\text{K}} \]

5. **Considering Molar Entropy**: When considering one mole of a substance, we express the unit of entropy as:
\[ \text{Unit of Entropy} = \frac{\text{J}}{\text{K} \cdot \text{mol}} = \text{J K}^{-1} \text{mol}^{-1} \]

6. **Conclusion**: Therefore, the unit of entropy is:
\[ \text{J K}^{-1} \text{mol}^{-1} \]
This matches with option number one provided in the question.

**Final Answer**: The unit of entropy is \( \text{J K}^{-1} \text{mol}^{-1} \).

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