On the addition of mineral acid to an aqueous solution of borax, the compound formed is:

Options

A. Boron oxide
B. Orthoboric acid
C. Metaboric acid
D. Pyroboric acid

Answer

To solve the question, we need to determine what compound is formed when mineral acid is added to an aqueous solution of borax. Here’s the step-by-step solution:

### Step 1: Identify the composition of borax
Borax is a compound with the formula Na₂B₄O₇. It is a sodium borate mineral.

### Step 2: Write the reaction with mineral acid
When mineral acid (for example, hydrochloric acid, HCl) is added to an aqueous solution of borax, the reaction can be represented as follows:

\[ \text{Na}_2\text{B}_4\text{O}_7 + \text{HCl} + \text{H}_2\text{O} \]

### Step 3: Determine the products of the reaction
The reaction between borax and mineral acid leads to the formation of orthoboric acid (H₃BO₃) and sodium chloride (NaCl). The balanced reaction can be written as:

\[ \text{Na}_2\text{B}_4\text{O}_7 + 2 \text{HCl} + 5 \text{H}_2\text{O} \rightarrow 4 \text{H}_3\text{BO}_3 + 2 \text{NaCl} \]

### Step 4: Identify the compound formed
From the balanced reaction, we see that the main product formed is orthoboric acid (H₃BO₃).

### Conclusion
Thus, the compound formed on the addition of mineral acid to an aqueous solution of borax is **orthoboric acid**.

### Final Answer
The correct answer is **orthoboric acid** (option 2).

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