Which of the following statements are true for `H_(3)BO_(3)` ?

Options

A. It is weak monobasic acid and a Lewis acid.
B. It does not act as a proton donor but acts as an acid by accepting hydroxyl ions.
C. It has a layer structure in which `BO_(3)` units are joined by van der
Waals forces of attraction.
D. It is obtained by heating borax with conc. sulphuric acid

Explanation

To determine which statements about H₃BO₃ (boric acid) are true, we will analyze each statement one by one.

### Step 1: Analyze the first statement
**Statement 1:** H₃BO₃ is a weak monobasic acid and a Lewis acid.

- Boric acid (H₃BO₃) is indeed considered a weak acid. It does not donate protons (H⁺) in the same way that typical acids do. Instead, it acts as a Lewis acid by accepting hydroxyl ions (OH⁻) from water, forming the tetrahydroxyborate ion (BO₃H₄⁻).
- Therefore, this statement is **true**.

### Step 2: Analyze the second statement
**Statement 2:** H₃BO₃ does not act as a proton donor but acts as an acid by accepting hydroxyl ions.

- This aligns with the behavior of boric acid. It does not donate protons directly but instead reacts with water to form the tetrahydroxyborate ion, confirming its role as a Lewis acid.
- Thus, this statement is also **true**.

### Step 3: Analyze the third statement
**Statement 3:** H₃BO₃ has a layered structure in which BO₃ units are joined by Van der Waals forces.

- The structure of boric acid consists of BO₃ units that are linked by hydrogen bonds, not Van der Waals forces. The layered structure is stabilized by these hydrogen bonds, which are stronger than Van der Waals forces.
- Therefore, this statement is **false**.

### Step 4: Analyze the fourth statement
**Statement 4:** H₃BO₃ is obtained by heating borax with concentrated sulfuric acid.

- Boric acid can be produced by the reaction of borax (Na₂B₄O₇) with concentrated sulfuric acid, resulting in the formation of H₃BO₃ and sodium sulfate (Na₂SO₄).
- Hence, this statement is **true**.

### Conclusion:
The true statements about H₃BO₃ are:
1. H₃BO₃ is a weak monobasic acid and a Lewis acid (True).
2. H₃BO₃ does not act as a proton donor but acts as an acid by accepting hydroxyl ions (True).
3. H₃BO₃ has a layered structure in which BO₃ units are joined by Van der Waals forces (False).
4. H₃BO₃ is obtained by heating borax with concentrated sulfuric acid (True).

### Final Answer:
The true statements are 1, 2, and 4.

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