Ionisation of boric acid in aqusous medium gives which one of the following?

Options

A. `[B(OH)_(4)]^(-)`
B. `[B(OH)_(2)O]^(-)`
C. `[B(OH)O_(2)]^(2-)`
D. `[BO_(3)]^(3-)`

Answer

To solve the question regarding the ionization of boric acid in an aqueous medium, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Chemical Formula of Boric Acid**:
- The chemical formula of boric acid is \( H_3BO_3 \). It can also be represented as \( B(OH)_3 \).

2. **Understand the Ionization Process**:
- When boric acid is dissolved in water, it undergoes hydrolysis. This means it reacts with water to form other species.

3. **Write the Hydrolysis Reaction**:
- The hydrolysis of boric acid can be represented by the following reaction:
\[ B(OH)_3 + H_2O \rightleftharpoons B(OH)_4^- + H_3O^+ \]
- In this reaction, boric acid accepts a hydroxide ion (\( OH^- \)) from water, leading to the formation of the tetrahydroxyborate ion (\( B(OH)_4^- \)) and hydronium ion (\( H_3O^+ \)).

4. **Determine the Nature of Boric Acid**:
- Boric acid is classified as a Lewis acid because it does not donate protons (\( H^+ \)) directly; instead, it accepts hydroxide ions.

5. **Identify the Correct Answer**:
- From the hydrolysis reaction, we can see that the product formed is \( B(OH)_4^- \). Therefore, the correct answer to the question is the species \( B(OH)_4^- \).

### Final Answer:
The ionization of boric acid in an aqueous medium gives \( B(OH)_4^- \).

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