For `H_(3)PO_(3)` and `H_(3)PO_(4)` the correct choice is

Options

A. `H_(3)PO_(3)` is dibasic and reducing
B. `H_(3)PO_(3)` is dibasic and non-reducing
C. `H_(3)PO_(4)` is tribasic and reducing
D. `H_(3)PO_(3)` is tribasic and non-reducing.

Answer

To analyze the properties of the acids \( H_3PO_3 \) and \( H_3PO_4 \), we will go through the following steps:

### Step 1: Determine the structures of \( H_3PO_3 \) and \( H_3PO_4 \)

1. **Structure of \( H_3PO_3 \)**:
- The structure consists of a phosphorus atom (P) bonded to three oxygen atoms (O).
- One of the oxygen atoms is double-bonded to phosphorus (P=O), while the other two are hydroxyl groups (–OH).
- The general structure can be represented as:
\[ \text{O} \\ || \\ \text{P} - \text{OH} \\ | \\ \text{OH} \]
- This gives \( H_3PO_3 \) a tetrahedral geometry.

2. **Structure of \( H_3PO_4 \)**:
- The structure consists of a phosphorus atom bonded to four oxygen atoms.
- One oxygen is double-bonded (P=O), and the other three are hydroxyl groups (–OH).
- The structure can be represented as:
\[ \text{O} \\ || \\ \text{P} - \text{OH} \\ | \\ \text{OH} \\ | \\ \text{OH} \]
- This also has a tetrahedral geometry.

### Step 2: Determine the oxidation states of phosphorus in both acids

1. **For \( H_3PO_3 \)**:
- Let the oxidation state of phosphorus be \( x \).
- The equation based on the charges is:
\[ x + 3(+1) + 3(-2) = 0 \\ x + 3 - 6 = 0 \\ x = +3 \]
- Therefore, the oxidation state of phosphorus in \( H_3PO_3 \) is +3.

2. **For \( H_3PO_4 \)**:
- Let the oxidation state of phosphorus be \( x \).
- The equation is:
\[ x + 3(+1) + 4(-2) = 0 \\ x + 3 - 8 = 0 \\ x = +5 \]
- Therefore, the oxidation state of phosphorus in \( H_3PO_4 \) is +5.

### Step 3: Determine the acidity and reducing nature of the acids

1. **Acidity**:
- \( H_3PO_3 \) has two hydroxyl groups, making it dibasic (can donate 2 protons).
- \( H_3PO_4 \) has three hydroxyl groups, making it tribasic (can donate 3 protons).

2. **Reducing nature**:
- \( H_3PO_3 \) with phosphorus in the +3 oxidation state can act as a reducing agent because it can be oxidized to +5.
- \( H_3PO_4 \) with phosphorus in the +5 oxidation state cannot be oxidized further, hence it does not exhibit reducing properties.

### Conclusion

Based on the analysis:
- \( H_3PO_3 \) is dibasic and reducing in nature.
- \( H_3PO_4 \) is tribasic and non-reducing in nature.

### Final Answer
The correct choice is:
- \( H_3PO_3 \) is dibasic and reducing.
- \( H_3PO_4 \) is tribasic and non-reducing.

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