Among the chlorides of alkali metals, what is the decreasing order of hydration ?

Options

A. NaCl > RbCl > LiCl > CsCl
B. LiCl > CsCl >KCl > RbCl >NaCl
C. LiCl > NaCl > KCl > RbCl g>CsCl
D. All are equatlly hydrated as halide is same

Answer

To determine the decreasing order of hydration among the chlorides of alkali metals (LiCl, NaCl, KCl, RbCl, CsCl), we need to consider the hydration energy, which is influenced by the size of the ions involved.

### Step-by-Step Solution:

1. **Identify the Alkali Metals**: The alkali metals include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs).

2. **Understand Hydration Energy**: Hydration energy refers to the energy released when one mole of an ion is surrounded by water molecules. Smaller ions have higher hydration energy due to stronger electrostatic attraction with water molecules.

3. **Analyze the Size of Ions**: As we move down the group from Li to Cs, the size of the alkali metal ions increases:
- Li⁺ < Na⁺ < K⁺ < Rb⁺ < Cs⁺

4. **Relate Size to Hydration Energy**: Since smaller ions have a greater ability to attract water molecules, they will have higher hydration energy. Therefore, the trend in hydration energy for the alkali metals is:
- Li⁺ > Na⁺ > K⁺ > Rb⁺ > Cs⁺

5. **Determine the Order for Chlorides**: Since the hydration energy of the chloride salts corresponds to the hydration energy of the metal cations, we can conclude:
- LiCl > NaCl > KCl > RbCl > CsCl

6. **Final Decreasing Order of Hydration**: Thus, the decreasing order of hydration among the chlorides of alkali metals is:
- LiCl > NaCl > KCl > RbCl > CsCl

### Conclusion:
The final answer for the decreasing order of hydration among the chlorides of alkali metals is:
**LiCl > NaCl > KCl > RbCl > CsCl**