Which one is the wrong statement ?

Options

A. Anhydrous `AlCl_3` exists as `Al_2Cl_6` (dimer)
B. `Al_2Cl_6` contains `3c-4e^(-)` bonds
C. Anhydrous `AlCl_3` fumes in moist air
D. Anhydrous `AlCl_3` is ionic

Answer

To determine which statement about anhydrous AlCl3 is incorrect, let's analyze each statement step by step.

### Step 1: Analyze the First Statement
**Statement:** Anhydrous AlCl3 exists as Al2Cl6 dimer.

- **Explanation:** Anhydrous AlCl3 is known to exist in a dimeric form as Al2Cl6. This occurs because AlCl3 is electron deficient and dimerizes to achieve stability. Therefore, this statement is **correct**.

### Step 2: Analyze the Second Statement
**Statement:** Al2Cl6 contains three center four-electron bonds.

- **Explanation:** In the structure of Al2Cl6, there are three center-four electron bonds formed between the aluminum atoms and chlorine atoms. Each aluminum atom is bonded to three chlorine atoms through covalent bonds, and there is a dative bond involving lone pairs from chlorine. Thus, this statement is also **correct**.

### Step 3: Analyze the Third Statement
**Statement:** Anhydrous AlCl3 fumes in moist air.

- **Explanation:** Anhydrous AlCl3 reacts with moisture in the air to form hydrochloric acid (HCl) and aluminum hydroxide (Al(OH)3). This reaction produces white fumes of HCl gas when it comes into contact with moist air. Hence, this statement is **correct**.

### Step 4: Analyze the Fourth Statement
**Statement:** Anhydrous AlCl3 is ionic in nature.

- **Explanation:** Anhydrous AlCl3 is primarily covalent due to the nature of the bonding in the dimer Al2Cl6. While it can form ionic compounds when hydrated (like AlCl3·6H2O), in its anhydrous state, it does not exhibit ionic characteristics. Therefore, this statement is **incorrect**.

### Conclusion
The wrong statement is: **Anhydrous AlCl3 is ionic in nature.**

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