Which of the following acids is monobasic?

Options

A. Hypophosphorous acid `(H_(3)PO_(2))`
B. Orthophosphoric acid `(H_(3)PO_(4))`
C. Pyrophosphoric acid `(H_(4)P_(2)O_(7))`
D. Hypophosphoric acid `(H_(4)P_(2)O_(6))`

Explanation

To determine which of the given acids is monobasic, we need to analyze each acid based on the number of hydrogen ions (H⁺) they can donate when dissolved in water. A monobasic acid can donate only one H⁺ ion.

### Step-by-Step Solution:

1. **Understanding Monobasic Acids**:
- A monobasic acid is defined as an acid that can donate only one H⁺ ion in solution.

2. **Analyzing Hypophosphorous Acid (H₃PO₂)**:
- The formula for hypophosphorous acid is H₃PO₂.
- Its structure includes one hydroxyl group (–OH) that can donate one H⁺ ion.
- When H₃PO₂ dissociates, it releases one H⁺ ion:
\[ H₃PO₂ \rightarrow H⁺ + H₂PO₂⁻ \]
- Therefore, hypophosphorous acid is a monobasic acid.

3. **Analyzing Orthophosphoric Acid (H₃PO₄)**:
- The formula for orthophosphoric acid is H₃PO₄.
- It has three hydroxyl groups, which means it can donate three H⁺ ions:
\[ H₃PO₄ \rightarrow 3H⁺ + PO₄³⁻ \]
- Hence, orthophosphoric acid is a tribasic acid.

4. **Analyzing Pyrophosphoric Acid (H₄P₂O₇)**:
- The formula for pyrophosphoric acid is H₄P₂O₇.
- It has four hydroxyl groups, indicating it can donate four H⁺ ions:
\[ H₄P₂O₇ \rightarrow 4H⁺ + P₂O₇⁴⁻ \]
- Therefore, pyrophosphoric acid is a tetrabasic acid.

5. **Analyzing Hypophosphoric Acid (H₄P₂O₆)**:
- The formula for hypophosphoric acid is H₄P₂O₆.
- This acid also has multiple hydroxyl groups, allowing it to donate four H⁺ ions:
\[ H₄P₂O₆ \rightarrow 4H⁺ + P₂O₆⁴⁻ \]
- Thus, hypophosphoric acid is also a tetrabasic acid.

6. **Conclusion**:
- Among the acids analyzed, only hypophosphorous acid (H₃PO₂) is monobasic as it can donate only one H⁺ ion.

### Final Answer:
The monobasic acid among the options is **Hypophosphorous Acid (H₃PO₂)**.