Which of the following statements about `H_(3) BO_(3)` is not correct ?

Options

A. It has a layer structure in which planar `BO_(3)` units are joined by hydrogen bonds
B. It does not act as proton donor but acts as a Lewis acid by accepting hydroxyl ion
C. It is a strong tribasic acid
D. It is prepared by acidifying an aqueous solution of borax

Answer

To determine which statement about H₃BO₃ (Boric acid) is not correct, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Statement A: It has a layer structure in which planar BO₃ units are joined by hydrogen bonds.**
- H₃BO₃ has a layered structure where the boron atoms are surrounded by three oxygen atoms, forming planar BO₃ units. These units are indeed linked together by hydrogen bonds.
- **Conclusion:** This statement is correct.

2. **Statement B: It does not act as a proton donor but acts as a Lewis acid by accepting hydroxyl ions.**
- Boric acid (H₃BO₃) does not donate protons (H⁺) like typical acids. Instead, it can accept hydroxyl ions (OH⁻) to form tetrahydroxyborate (B(OH)₄⁻), acting as a Lewis acid.
- **Conclusion:** This statement is correct.

3. **Statement C: It is a strong tribasic acid.**
- Although H₃BO₃ has three hydroxyl groups, it does not behave as a strong tribasic acid. Instead, it acts as a Lewis acid and accepts hydroxyl ions rather than donating protons. Therefore, it does not fully dissociate into three protons in solution.
- **Conclusion:** This statement is incorrect.

4. **Statement D: It is prepared by acidifying an aqueous solution of borax.**
- Borax (Na₂B₄O₇·10H₂O) can be converted to boric acid by treating it with an acid (like HCl) in an aqueous solution. This reaction is well-known and valid.
- **Conclusion:** This statement is correct.

### Final Answer:
The statement that is not correct about H₃BO₃ is **C: It is a strong tribasic acid.**

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