Assertion (A): Among the alkali metals caesium salts exhibit the maximum conductance in aqueous solution.
Reaction (R ): The radii of the hydrated caesium is the highest among alkali metals.

Options

A. If both (A) and (R ) are correct and (R ) is the correct explanation of (A).
B. If both (A) and (R ) are correct, but (R ) is not the correct explanation of (A).
C. If (A) is correct, but (R ) is incorrect.
D. If (A) is incorrect, but (R ) is correct.

Explanation

To solve the question, we need to analyze both the assertion (A) and the reaction (R) provided.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that among the alkali metals, cesium salts exhibit the maximum conductance in aqueous solution.
- This is true because cesium ions (Cs⁺) are larger and have lower hydration energy compared to other alkali metal ions. This allows them to move more freely in solution, resulting in higher conductance.

2. **Understanding the Reaction (R)**:
- The reaction states that the radii of the hydrated cesium ion is the highest among alkali metals.
- This is incorrect. While cesium ions are large, when they are hydrated, they actually have the smallest hydrated radius among alkali metals. This is because the larger the ion, the fewer water molecules can surround it effectively due to steric hindrance.

3. **Conclusion**:
- The assertion (A) is correct: cesium salts do exhibit maximum conductance in aqueous solution.
- The reason (R) is incorrect: the hydrated radius of cesium is not the highest; it is actually the lowest among the alkali metals.
- Therefore, the correct answer is that the assertion is correct, but the reason is incorrect.

### Final Answer:
Assertion (A) is correct, but Reaction (R) is incorrect.

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