The oxoacid of phosphorus that reduces silver nitrate into metallic silver is

Options

A. `H_(3)PO_(2)`
B. `H_(4)P_(2)O_(6)`
C. `H_(3)PO_(4)`
D. `H_(4)P_(2)O_(7)`

Explanation

To solve the question regarding the oxoacid of phosphorus that can reduce silver nitrate to metallic silver, we will follow these steps:

### Step 1: Identify the oxoacids of phosphorus
The common oxoacids of phosphorus include:
1. Phosphorous acid (H₃PO₃)
2. Phosphoric acid (H₃PO₄)
3. Pyrophosphoric acid (H₄P₂O₇)
4. Phosphonic acid (H₃PO₂)

### Step 2: Understand the reducing properties
Among these acids, we need to identify which one has reducing properties. Reducing agents are substances that can donate electrons or reduce another substance.

### Step 3: Analyze the structure of the acids
- **H₃PO₃ (Phosphorous acid)**: Contains P-H bonds which can act as reducing agents.
- **H₃PO₄ (Phosphoric acid)**: Does not have P-H bonds and is not a reducing agent.
- **H₄P₂O₇ (Pyrophosphoric acid)**: Similar to phosphoric acid, it does not exhibit reducing properties.
- **H₃PO₂ (Phosphonic acid)**: Contains P-H bonds and can act as a reducing agent.

### Step 4: Determine the correct oxoacid
From the analysis, we find that:
- **H₃PO₃** and **H₃PO₂** both have P-H bonds.
- However, H₃PO₃ is known for its reducing properties, particularly in the context of reducing silver nitrate to metallic silver.

### Conclusion
The oxoacid of phosphorus that reduces silver nitrate into metallic silver is **H₃PO₃ (Phosphorous acid)**.