Pick out the stronger reducing agent among the following oxyacids of phosphorus

Options

A. Hypophosphorous acid
B. Phosphorous acid
C. Hypophosphoric acid
D. Pyrophosphorous acid

Answer

To determine the stronger reducing agent among the given oxyacids of phosphorus, we will analyze the structures and the number of P-H bonds in each acid. The more P-H bonds an acid has, the stronger its reducing ability.

### Step-by-Step Solution:

1. **Identify the Oxyacids**: The oxyacids of phosphorus given are:
- Hypophosphorous acid (H₃PO₂)
- Phosphorous acid (H₃PO₃)
- Hypophosphoric acid (H₄P₂O₆)
- Pyrophosphorous acid (H₄P₂O₅)

2. **Analyze the Structures**:
- **Hypophosphorous Acid (H₃PO₂)**:
- Structure: P(OH)₂H
- Number of P-H bonds: 2
- **Phosphorous Acid (H₃PO₃)**:
- Structure: P(OH)₃
- Number of P-H bonds: 1
- **Hypophosphoric Acid (H₄P₂O₆)**:
- Structure: P₂(OH)₄O₂
- Number of P-H bonds: 0 (as the structure involves P=O and P-OH)
- **Pyrophosphorous Acid (H₄P₂O₅)**:
- Structure: P₂(OH)₂O₃
- Number of P-H bonds: 2

3. **Count the P-H Bonds**:
- Hypophosphorous Acid: 2 P-H bonds
- Phosphorous Acid: 1 P-H bond
- Hypophosphoric Acid: 0 P-H bonds
- Pyrophosphorous Acid: 2 P-H bonds

4. **Determine the Strongest Reducing Agent**:
- Since the reducing ability increases with the number of P-H bonds, we compare the counts:
- Hypophosphorous Acid has 2 P-H bonds.
- Phosphorous Acid has 1 P-H bond.
- Hypophosphoric Acid has 0 P-H bonds.
- Pyrophosphorous Acid has 2 P-H bonds.
- Hypophosphorous Acid and Pyrophosphorous Acid both have 2 P-H bonds, but Hypophosphorous Acid is generally recognized as a stronger reducing agent due to its structure and stability.

5. **Conclusion**: The stronger reducing agent among the given oxyacids of phosphorus is **Hypophosphorous Acid (H₃PO₂)**.