`BO_(3)^(3-) + Conc. H_(2)SO_(4) + CH_(3) - CH_(2) - OH overset("ignite") to underset("Green flame")((A))` . What is the oxidation number of central atom that is responsible for green in compound (A) ?

Explanation

To determine the oxidation number of the central atom responsible for the green flame in compound (A), we will follow these steps:

### Step 1: Identify the Reactants
The reactants given in the question are the borate ion \( \text{BO}_3^{3-} \), concentrated sulfuric acid \( \text{H}_2\text{SO}_4 \), and ethanol \( \text{C}_2\text{H}_5\text{OH} \).

### Step 2: Reaction of Borate Ion with Concentrated Sulfuric Acid
When the borate ion reacts with concentrated sulfuric acid, it forms boric acid \( \text{H}_3\text{BO}_3 \) and sodium sulfate \( \text{Na}_2\text{SO}_4 \). The reaction can be represented as:
\[ \text{Na}_3\text{BO}_3 + \text{H}_2\text{SO}_4 \rightarrow \text{H}_3\text{BO}_3 + \text{Na}_2\text{SO}_4 \]

### Step 3: Reaction of Boric Acid with Ethanol
Next, boric acid reacts with ethanol to form ethyl borate \( \text{B(OCH}_2\text{CH}_3)_3 \) and water. The reaction can be represented as:
\[ \text{H}_3\text{BO}_3 + 3 \text{C}_2\text{H}_5\text{OH} \rightarrow \text{B(OCH}_2\text{CH}_3)_3 + 3 \text{H}_2\text{O} \]

### Step 4: Identify Compound (A)
The compound formed, which is responsible for the green flame, is ethyl borate \( \text{B(OCH}_2\text{CH}_3)_3 \).

### Step 5: Determine the Oxidation State of Boron in Ethyl Borate
In ethyl borate, boron (B) is the central atom. To determine its oxidation state, we consider the bonding:
- Each ethyl group \( \text{C}_2\text{H}_5 \) contributes a -1 charge to the boron.
- Boron typically has an oxidation state of +3 in its compounds.

Thus, in ethyl borate, the oxidation state of boron is +3.

### Conclusion
The oxidation number of the central atom (boron) responsible for the green flame in compound (A) is +3.

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