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

Explanation

To solve the question, we need to analyze the reaction and determine the oxidation state of the central atom in compound A that is responsible for the green flame.

### Step-by-Step Solution:

1. **Identify the Reactants**: The reactants are \( B_3^{3-} \) (boron trianion), concentrated \( H_2SO_4 \) (sulfuric acid), and \( CH_3-CH_2-OH \) (ethanol).

2. **Understand the Reaction**: When \( B_3^{3-} \) reacts with concentrated sulfuric acid and ethanol, it leads to the formation of a compound, which we will denote as compound A.

3. **Determine the Product**: The product formed from this reaction is \( B(C_2H_5O)_3 \). This indicates that boron is bonded to three ethoxy groups (\( C_2H_5O \)).

4. **Identify the Central Atom**: The central atom in compound A is boron (B).

5. **Determine the Oxidation State of Boron**: In the compound \( B(C_2H_5O)_3 \), boron is bonded to three ethoxy groups. Each ethoxy group contributes a -1 charge to the overall charge of boron. Since boron originally has a +3 charge in the \( B_3^{3-} \) state, we can calculate the oxidation state as follows:
- The overall charge of the compound must be neutral.
- Each \( C_2H_5O \) contributes -1, so three of them contribute -3.
- Therefore, the oxidation state of boron must be +3 to balance the -3 from the ethoxy groups.

6. **Conclusion**: The oxidation number of boron in compound A is +3.

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

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