Which of the following salt/s of `H_(3)PO_(3)` exists ?
(I)) `NaH_(2)PO_(3)` (II) `Na_(2)HPO_(3)` (III) `Na_(3)PO_(3)`

Options

A. I and II only
B. I, II and III
C. II and III only
D. III only

Answer

To determine which salts of \( H_3PO_3 \) (phosphorous acid) exist, we need to analyze the possible salts based on the structure and properties of the acid.

### Step-by-Step Solution:

1. **Identify the Acid**:
- The given acid is \( H_3PO_3 \), known as phosphorous acid. It is a diprotic acid, meaning it can donate two protons (H⁺ ions).

2. **Understand the Structure**:
- The structure of \( H_3PO_3 \) can be represented as:
\[ \text{P} = \text{O} \\ \text{H} - \text{O} - \text{P} - \text{O} - \text{H} \\ \text{H} - \text{O} - \text{P} - \text{O} \]
- This indicates that there are two replaceable hydrogen ions.

3. **Determine Possible Salts**:
- The possible salts formed from \( H_3PO_3 \) will be based on the replacement of these hydrogen ions by sodium ions (Na⁺).
- The possible salts are:
- \( NaH_2PO_3 \) - This salt is formed by replacing one hydrogen ion.
- \( Na_2HPO_3 \) - This salt is formed by replacing two hydrogen ions.
- \( Na_3PO_3 \) - This salt would require replacing all three hydrogen ions, which is not possible since \( H_3PO_3 \) can only donate two protons.

4. **Evaluate Each Option**:
- **Option I: \( NaH_2PO_3 \)** - Exists (one hydrogen replaced).
- **Option II: \( Na_2HPO_3 \)** - Exists (two hydrogens replaced).
- **Option III: \( Na_3PO_3 \)** - Does not exist (cannot replace all three hydrogens).

5. **Conclusion**:
- The salts that exist from \( H_3PO_3 \) are \( NaH_2PO_3 \) and \( Na_2HPO_3 \). Therefore, the correct answers are:
- I and II.

### Final Answer:
The salts of \( H_3PO_3 \) that exist are:
- (I) \( NaH_2PO_3 \)
- (II) \( Na_2HPO_3 \)