Which statement is not correct about `H_3BO_3` ?

Options

A. It is a strong tribasic acid
B. It has a layer structure in which planar `BO_3` units are joined by hydrogen bonds
C. It is prepared by acidifying an aqueous solution of borax
D. It does not act as proton donor but acts as a Lewis acid by accepting hydroxyl ion

Answer

To determine which statement is not correct about \( H_3BO_3 \) (boric acid), we will analyze the properties and characteristics of boric acid step by step.

### Step-by-Step Solution:

1. **Identify the Structure of \( H_3BO_3 \)**:
- Boric acid, \( H_3BO_3 \), is also known as ortho-boric acid. Its structure consists of boron (B) surrounded by three hydroxyl groups (OH). The molecular structure can be represented as:
\[ \text{B(OH)}_3 \]
- The boron atom is at the center, and the three hydroxyl groups are arranged around it.

**Hint**: Remember that the structure of boric acid is planar with boron at the center and hydroxyl groups attached.

2. **Determine the Acidic Nature of \( H_3BO_3 \)**:
- Boric acid is classified as a weak acid. It does not donate protons (H⁺) like typical acids. Instead, it acts as a Lewis acid by accepting hydroxyl ions (OH⁻) from water, forming tetrahydroxyborate ions.

**Hint**: Recall that Lewis acids accept electron pairs, while Brønsted acids donate protons.

3. **Evaluate the Preparation of \( H_3BO_3 \)**:
- Boric acid can be prepared by acidifying borax (sodium tetraborate, \( Na_2B_4O_7 \)) with sulfuric acid (\( H_2SO_4 \)). The reaction can be summarized as:
\[ Na_2B_4O_7 + H_2SO_4 + H_2O \rightarrow 4 H_3BO_3 + Na_2SO_4 \]

**Hint**: Focus on the reaction between borax and sulfuric acid to produce boric acid.

4. **Analyze the Statements**:
- **Statement 1**: "It is a strong tribasic acid." - This statement is incorrect because boric acid is a weak monobasic Lewis acid.
- **Statement 2**: "It has a layered structure in which planar BO3 units are joined by hydrogen bonds." - This statement is correct.
- **Statement 3**: "It is prepared by acidifying an aqueous solution of borax." - This statement is also correct.
- **Statement 4**: "It does not act as a proton donor but acts as a Lewis acid by accepting hydroxyl ions." - This statement is correct.

**Hint**: Identify which statement contradicts the known properties of boric acid.

5. **Conclusion**:
- The statement that is not correct about \( H_3BO_3 \) is the first one: "It is a strong tribasic acid." Therefore, the correct answer is that this statement is false.

### Final Answer:
The statement that is not correct about \( H_3BO_3 \) is: **"It is a strong tribasic acid."**