Anhydrous `AlCl_(3)` is obtained when :

Options

A. Aluminium oxide reacts with `HCl`
B. Aluminium reacts with `HCl`
C. Aluminium is heated in a current of dry `Cl_(2)`
D. Aluminium hydroxide reacts with `HCl`.

Answer

To determine how anhydrous AlCl₃ is obtained, we will analyze the given options step by step.

### Step 1: Analyze the first option
**Option A: Aluminum oxide reacts with HCl.**
- The reaction can be represented as:
\[ \text{Al}_2\text{O}_3 + 6\text{HCl} \rightarrow 2\text{AlCl}_3 + 3\text{H}_2\text{O} \]
- This reaction produces AlCl₃ in an aqueous form along with water. Therefore, it does not yield anhydrous AlCl₃.

**Hint:** Check if the reaction produces water or if it remains in a dry form.

### Step 2: Analyze the second option
**Option B: Aluminum reacts with HCl.**
- The reaction can be represented as:
\[ 2\text{Al} + 6\text{HCl} \rightarrow 2\text{AlCl}_3 + 3\text{H}_2 \]
- Similar to the first option, this reaction also produces AlCl₃ in an aqueous solution, along with hydrogen gas. Thus, it does not yield anhydrous AlCl₃.

**Hint:** Consider the state of the product formed in the reaction.

### Step 3: Analyze the third option
**Option C: Aluminum is heated in a current of dry Cl₂.**
- The reaction can be represented as:
\[ 2\text{Al} + 3\text{Cl}_2 \rightarrow \text{Al}_2\text{Cl}_6 \]
- When aluminum is heated in dry chlorine gas, it forms Al₂Cl₆, which is the dimer of AlCl₃. When this dimer is heated or treated appropriately, it can yield anhydrous AlCl₃.

**Hint:** Look for reactions that involve dry conditions or high temperatures.

### Step 4: Analyze the fourth option
**Option D: Aluminum hydroxide reacts with HCl.**
- The reaction can be represented as:
\[ \text{Al(OH)}_3 + 3\text{HCl} \rightarrow \text{AlCl}_3 + 3\text{H}_2\text{O} \]
- Similar to the previous options, this reaction produces AlCl₃ along with water, indicating that it does not yield anhydrous AlCl₃.

**Hint:** Again, check if water is produced in the reaction.

### Conclusion
After analyzing all the options, the only reaction that yields anhydrous AlCl₃ is the one where aluminum is heated in a current of dry chlorine gas. Therefore, the correct answer is:

**Correct Option: C - Aluminum is heated in a current of dry Cl₂.**