Anhydrous aluminium chloride fumes in moist air owing to the formation of:

Options

A. Gaseous aluminium chloride
B. chlorine
C. chlorine dioxide
D. hydrogen chloride

Answer

To solve the question regarding why anhydrous aluminium chloride (AlCl3) fumes in moist air, we can break it down into a series of steps:

### Step 1: Understanding Anhydrous Aluminium Chloride
Anhydrous aluminium chloride (AlCl3) is a white solid that can exist in a dimeric form (Al2Cl6) in the gas phase. It is known for its ability to absorb moisture from the air.

**Hint:** Recall that "anhydrous" means without water, and consider how it interacts with moisture.

### Step 2: Reaction with Moist Air
When anhydrous aluminium chloride is exposed to moist air, it reacts with water (H2O) present in the air. This reaction leads to the formation of aluminium hydroxide (Al(OH)3) and hydrogen chloride (HCl).

**Hint:** Think about what happens when a dry substance comes into contact with water.

### Step 3: Writing the Chemical Equation
The reaction can be represented by the following equation:
\[ \text{AlCl}_3 + 3 \text{H}_2\text{O} \rightarrow \text{Al(OH)}_3 + 3 \text{HCl} \]
In this equation, one mole of AlCl3 reacts with three moles of water to produce one mole of aluminium hydroxide and three moles of hydrogen chloride.

**Hint:** Pay attention to the stoichiometry of the reaction, which indicates the proportions of reactants and products.

### Step 4: Identifying the Fumes
The gaseous product formed during this reaction is hydrogen chloride (HCl), which is responsible for the fuming observed when anhydrous aluminium chloride is placed in moist air. The fumes are due to the release of HCl gas.

**Hint:** Consider which product of the reaction is a gas and how it might manifest as fumes.

### Step 5: Conclusion
Thus, the reason anhydrous aluminium chloride fumes in moist air is due to the formation of hydrogen chloride (HCl) gas along with aluminium hydroxide (Al(OH)3).

**Final Answer:** Anhydrous aluminium chloride fumes in moist air owing to the formation of hydrogen chloride (HCl).

### Summary of Steps:
1. Understand what anhydrous aluminium chloride is.
2. Recognize its reaction with moisture in the air.
3. Write the balanced chemical equation for the reaction.
4. Identify the gaseous product responsible for the fumes.
5. Conclude with the answer.