Which of the following correctly explains the nature of boric acid in aqueous medium :

Options

A. `H_3BO_(3) overset(H_2O)(rarr) H_3^(+)O + H_2BO_(3)^(-)`
B. `H_3BO_3 overset(2H_2O)(rarr) 2H_3^(+)O + HBO_(3)^(2-)`
C. `H_3BO_3 overset(3H_2O)(rarr) 3H_3^(+)O + BO_(3)^(3-)`
D. `H_3BO_3 overset(H_2O)(rarr)[B(OH)_(4)]^(-) + H^(+)`

Answer

To determine the nature of boric acid (H₃BO₃) in aqueous medium, we will analyze its behavior according to the Bronsted-Lowry and Lewis acid-base theories.

### Step-by-Step Solution:

1. **Understanding Boric Acid**:
- Boric acid (H₃BO₃) is a weak acid that can interact with water.
- In aqueous solutions, it does not dissociate in the same way as strong acids.

2. **Dissociation in Water**:
- When boric acid is added to water, it can be represented by the reaction:
\[ H_3BO_3 + H_2O \rightleftharpoons B(OH)_4^- + H^+ \]
- This shows that boric acid can release a proton (H⁺) when it reacts with water.

3. **Bronsted-Lowry Concept**:
- According to the Bronsted-Lowry theory, an acid is a substance that can donate a proton (H⁺).
- In this case, boric acid acts as a proton donor, thus behaving as an acid.

4. **Lewis Concept**:
- According to the Lewis theory, an acid is defined as a substance that can accept a pair of electrons.
- Boric acid can accept a lone pair of electrons from water, which further supports its classification as an acid.

5. **Monobasic Nature**:
- Boric acid is classified as a monobasic acid because it can donate only one proton (H⁺) per molecule in the reaction with water.

6. **Conclusion**:
- Based on the above analysis, boric acid in aqueous medium behaves as a weak acid that can donate a proton and accept electron pairs, confirming its nature as a monobasic acid.

### Final Answer:
The correct explanation for the nature of boric acid in aqueous medium is that it acts as a weak acid according to both Bronsted-Lowry and Lewis definitions, and it is classified as a monobasic acid.

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