Aluminium reacts with NaOH and forms compound 'X'. If the coordination number of aluminium in 'X' is 6, the correct formula of X is

Options

A. `[Al(H_(2)O)_(4)(OH)_(2)]^(+)`
B. `[Al(H_(2)O)_(3)(OH)_(3)]`
C. `[Al(H_(2)O)_(2)(OH)_(4)]^(-)`
D. `[Al(H_(2)O)_(6)(OH)_(3)]`

Answer

To determine the correct formula of the compound 'X' formed when aluminium reacts with NaOH, we can follow these steps:

### Step 1: Understand the Reaction
Aluminium (Al) reacts with sodium hydroxide (NaOH) in a basic medium. This reaction typically leads to the formation of aluminate ions.

### Step 2: Identify the Product
When aluminium reacts with NaOH, it forms sodium aluminate. The general reaction can be represented as:
\[ 2 \text{Al} + 2 \text{NaOH} + 2 \text{H}_2\text{O} \rightarrow 2 \text{NaAl(OH)}_4 \]
This can further dehydrate to form sodium meta-aluminate.

### Step 3: Determine the Coordination Number
The question states that the coordination number of aluminium in the compound 'X' is 6. In coordination chemistry, a coordination number of 6 typically indicates an octahedral geometry, which is common for aluminium complexes.

### Step 4: Write the Formula
Given that the coordination number of aluminium in 'X' is 6, the correct formula for the compound formed is sodium meta-aluminate, which can be represented as:
\[ \text{NaAlO}_2 \]
However, in the context of the reaction and the coordination number, the more appropriate representation considering the presence of water and hydroxide ions is:
\[ \text{NaAl(OH)}_4 \]
This can be simplified to sodium meta-aluminate as:
\[ \text{NaAlO}_3 \]

### Conclusion
The correct formula of compound 'X' formed when aluminium reacts with NaOH, considering the coordination number of aluminium is 6, is:
\[ \text{NaAlO}_3 \]

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