Which of the Phosphorus oxoacid can create silver mirror from `AgNO_3` solution?

Options

A. `H_4P_2O_8`
B. `H_3PO_3`
C. `H_4P_2O_7`
D. `H_4P_2O_6`

Answer

To solve the question of which phosphorus oxoacid can create a silver mirror from AgNO3 solution, we need to analyze the properties of phosphorus oxoacids and their ability to act as reducing agents.

### Step-by-Step Solution:

1. **Identify Phosphorus Oxoacids**:
The common phosphorus oxoacids include:
- Orthophosphoric acid (H3PO4)
- Phosphorous acid (H3PO3)
- Hypophosphorous acid (H3PO2)
- Phosphoric acid (H3PO4)

2. **Understand the Silver Mirror Test**:
The silver mirror test involves the reduction of silver ions (Ag+) to metallic silver (Ag). This is typically done using a reducing agent. The formation of a silver mirror is indicative of a successful reduction reaction.

3. **Check the Reducing Properties**:
Among the phosphorus oxoacids, we need to determine which one can act as a strong reducing agent:
- **H3PO4 (Orthophosphoric acid)**: Generally, it does not act as a reducing agent.
- **H3PO3 (Phosphorous acid)**: This acid is known to be a strong reducing agent and can reduce Ag+ to Ag.
- **H3PO2 (Hypophosphorous acid)**: This is also a reducing agent, but it is less commonly used in this context.

4. **Reaction with Silver Nitrate**:
The reaction of phosphorous acid (H3PO3) with silver nitrate (AgNO3) can be represented as:
\[ \text{H3PO3} + 2 \text{AgNO3} + \text{H2O} \rightarrow 2 \text{Ag} + 2 \text{HNO3} + \text{H3PO4} \]
In this reaction, H3PO3 reduces Ag+ ions to metallic silver, resulting in the formation of a silver mirror.

5. **Conclusion**:
Based on the analysis, the phosphorus oxoacid that can create a silver mirror from AgNO3 solution is **H3PO3 (Phosphorous acid)**.

### Final Answer:
The correct option is **H3PO3**.