The no.of conjugate acid-base pairs present in the aqueous solution of `H_(3)PO_(3)` , is

Options

A. 2
B. 3
C. 4
D. 5

Answer

To determine the number of conjugate acid-base pairs present in the aqueous solution of \( H_3PO_3 \) (phosphorous acid), we can follow these steps:

### Step 1: Identify the structure of \( H_3PO_3 \)
Phosphorous acid, \( H_3PO_3 \), has three hydrogen atoms, two of which are acidic. The structure can be represented as:
\[ H_3PO_3 \]

### Step 2: Determine the dissociation steps
Phosphorous acid can dissociate in two steps:
1. The first dissociation:
\[ H_3PO_3 \rightleftharpoons H^+ + H_2PO_3^- \]
- Here, \( H_3PO_3 \) acts as an acid, and \( H_2PO_3^- \) is its conjugate base.

2. The second dissociation:
\[ H_2PO_3^- \rightleftharpoons H^+ + HPO_3^{2-} \]
- In this step, \( H_2PO_3^- \) acts as an acid, and \( HPO_3^{2-} \) is its conjugate base.

### Step 3: Identify the conjugate acid-base pairs
From the dissociation reactions, we can identify the conjugate acid-base pairs:
1. The first pair:
- Acid: \( H_3PO_3 \)
- Conjugate Base: \( H_2PO_3^- \)

2. The second pair:
- Acid: \( H_2PO_3^- \)
- Conjugate Base: \( HPO_3^{2-} \)

### Step 4: Count the conjugate acid-base pairs
We have identified two conjugate acid-base pairs:
1. \( (H_3PO_3, H_2PO_3^-) \)
2. \( (H_2PO_3^-, HPO_3^{2-}) \)

Thus, the total number of conjugate acid-base pairs present in the aqueous solution of \( H_3PO_3 \) is **2**.

### Final Answer
The number of conjugate acid-base pairs present in the aqueous solution of \( H_3PO_3 \) is **2**.

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