Anhydrous `MgCl_(2)` is obatined by heating hydrate salt, `MgCl_(2).6H_(2)O`.

Options

A. Strongly in air
B. In presnence of coke
C. In presence of conc `H_(2)SO_(4)` which absorbs moisture
D. In presence of dry `HCl` gas

Answer

To obtain anhydrous magnesium chloride (MgCl₂) from its hydrate, magnesium chloride hexahydrate (MgCl₂·6H₂O), we need to follow these steps:

### Step-by-Step Solution:

1. **Identify the Hydrate**:
- The hydrate we are starting with is magnesium chloride hexahydrate, represented as MgCl₂·6H₂O. This compound contains magnesium chloride along with six water molecules.

2. **Heating the Hydrate**:
- When we heat MgCl₂·6H₂O, the water molecules associated with the magnesium chloride begin to evaporate. The process of heating will drive off the water, resulting in the formation of anhydrous magnesium chloride.

3. **Chemical Reaction**:
- The reaction can be represented as:
\[ \text{MgCl}_2 \cdot 6\text{H}_2\text{O} \xrightarrow{\text{heat}} \text{MgCl}_2 + 6\text{H}_2\text{O} \]
- This shows that upon heating, the hydrate loses its water molecules and converts to anhydrous MgCl₂.

4. **Conditions for Heating**:
- It is important to note that while heating MgCl₂·6H₂O, the presence of dry HCl gas can facilitate the process and ensure that no moisture is reabsorbed, which could otherwise hinder the formation of anhydrous MgCl₂.

5. **Conclusion**:
- Therefore, the correct method to obtain anhydrous MgCl₂ from MgCl₂·6H₂O is by heating it in the presence of dry hydrochloric acid (HCl).

### Final Answer:
Anhydrous MgCl₂ is obtained by heating MgCl₂·6H₂O in the presence of dry HCl.

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