`Na_(2)B_(4)O_(7) + X to H_(3) BO_(3)`. What is X in the reaction

Options

A. Aqueous solution of NaOH
B. Dilute nitric acid
C. Conc. `H_(2)SO_(4)` of HCI
D. water

Explanation

To solve the question `Na_(2)B_(4)O_(7) + X → H_(3)BO_(3)`, we need to identify the substance X that reacts with sodium tetraborate (borax) to produce boric acid (H₃BO₃).

### Step-by-Step Solution:

1. **Identify the Reactant**: The reactant given is sodium tetraborate, which is represented as Na₂B₄O₇. This compound is commonly known as borax.

2. **Identify the Product**: The product of the reaction is boric acid, represented as H₃BO₃.

3. **Determine the Type of Reaction**: The reaction involves the conversion of borax into boric acid. This typically occurs through a reaction with an acid.

4. **Identify Possible Acids**: Common acids that can react with borax include:
- Hydrochloric acid (HCl)
- Sulfuric acid (H₂SO₄)
- Other mineral acids

5. **Write the Reaction**: The most common reaction involves borax reacting with hydrochloric acid:
\[ Na_2B_4O_7 + 6HCl + 3H_2O \rightarrow 4H_3BO_3 + 2NaCl \]
This shows that borax reacts with hydrochloric acid and water to produce boric acid and sodium chloride.

6. **Conclusion**: Therefore, X in the reaction is hydrochloric acid (HCl).

### Final Answer:
X = HCl (Hydrochloric acid)

---