Which of the following is most soluble in water?

Options

A. `CsClO_(4)`
B. `NaClO_(4)`
C. `KClO_(4)`
D. `LiClO_(4)`

Answer

To determine which of the given compounds is most soluble in water, we will analyze the solubility of cesium perchlorate (CsClO4), sodium perchlorate (NaClO4), potassium perchlorate (KClO4), and lithium perchlorate (LiClO4).

### Step-by-Step Solution:

1. **Identify the Compounds**: We have four compounds to consider:
- Cesium perchlorate (CsClO4)
- Sodium perchlorate (NaClO4)
- Potassium perchlorate (KClO4)
- Lithium perchlorate (LiClO4)

2. **Analyze the Cations**: The cations present in these compounds are:
- Cs⁺ (Cesium ion)
- Na⁺ (Sodium ion)
- K⁺ (Potassium ion)
- Li⁺ (Lithium ion)

3. **Compare Cation Sizes**: The size of the cations increases in the following order:
- Li⁺ < Na⁺ < K⁺ < Cs⁺
This means lithium ion is the smallest, while cesium ion is the largest.

4. **Understand Hydration Energy**: Hydration energy is the energy released when ions are surrounded by water molecules. Smaller ions have higher charge density, which leads to stronger interactions with water molecules and thus higher hydration energy.

5. **Relate Hydration Energy to Solubility**: The greater the hydration energy, the more soluble the compound tends to be in water. Therefore, the solubility order will correlate with the size of the cation:
- Li⁺ has the highest hydration energy due to its small size.
- Na⁺ has moderate hydration energy.
- K⁺ has lower hydration energy than Na⁺.
- Cs⁺ has the lowest hydration energy due to its larger size.

6. **Determine the Solubility Order**: Based on the hydration energies, we can establish the solubility order:
- LiClO4 > NaClO4 > KClO4 > CsClO4

7. **Conclusion**: Therefore, the most soluble compound in water among the given options is lithium perchlorate (LiClO4).

### Final Answer:
The most soluble compound in water is **LiClO4**.

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