Chlorides of which of the following metals crystallize from an aqueous solution as hydrates?

Options

A. Li
B. Na
C. K
D. Mg

Answer

To determine which chlorides crystallize from an aqueous solution as hydrates, we need to analyze the chlorides of the given metals: lithium, sodium, potassium, and magnesium.

### Step-by-Step Solution:

1. **Identify the Chlorides**:
- Lithium forms lithium chloride (LiCl).
- Sodium forms sodium chloride (NaCl).
- Potassium forms potassium chloride (KCl).
- Magnesium forms magnesium chloride (MgCl2).

2. **Examine Hydration Properties**:
- Hydrates are compounds that contain water molecules within their crystal structure.
- We need to check which of the above chlorides can form hydrates.

3. **Lithium Chloride (LiCl)**:
- Lithium chloride can crystallize as a hydrate. Specifically, it can form LiCl·2H2O (dihydrate).

4. **Sodium Chloride (NaCl)**:
- Sodium chloride does not typically form hydrates. It crystallizes as anhydrous NaCl.

5. **Potassium Chloride (KCl)**:
- Similar to sodium chloride, potassium chloride does not form hydrates and crystallizes as anhydrous KCl.

6. **Magnesium Chloride (MgCl2)**:
- Magnesium chloride can crystallize as a hydrate. It commonly forms MgCl2·6H2O (hexahydrate).

7. **Conclusion**:
- The metals whose chlorides crystallize from an aqueous solution as hydrates are lithium (Li) and magnesium (Mg).

### Final Answer:
The chlorides of lithium and magnesium crystallize from an aqueous solution as hydrates.

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