Among the following an acidic salt is

Options

A. `NaH_(2)PO_(2)`
B. `NaH_(2)PO_(3)`
C. `Na_(2)HPO_(3)`
D. `Na_(3)PO_(4)`

Answer

To determine which of the given salts is an acidic salt, we need to analyze each option based on the definition of acidic salts and their formation from acids.

### Step-by-Step Solution:

1. **Understanding Acidic Salts**:
- Acidic salts are formed from the partial neutralization of diprotic or polyprotic acids. They contain one or more replaceable hydrogen ions (H⁺) that can still contribute to acidity in a solution.

2. **Analyzing the Options**:
- We have four salts to consider: NaH2PO2, NaH2PO3, Na2HPO3, and Na3PO4.

3. **Examining NaH2PO2**:
- This salt is derived from the acid NaH3PO2 (hypophosphorous acid).
- The structure of NaH3PO2 shows that it has only one acidic hydrogen (H), which means when it forms NaH2PO2, it loses that hydrogen.
- Therefore, NaH2PO2 does not have any acidic hydrogen left and is not an acidic salt.

4. **Examining NaH2PO3**:
- This salt is derived from NaH3PO3 (phosphorous acid).
- The structure of NaH3PO3 indicates that it has two acidic hydrogens.
- When one hydrogen is replaced by sodium, NaH2PO3 still retains one acidic hydrogen.
- Thus, NaH2PO3 is an acidic salt.

5. **Examining Na2HPO3**:
- This salt is formed from NaH3PO3 as well, but here, two hydrogens are replaced by sodium ions.
- Since both acidic hydrogens are removed, Na2HPO3 does not retain any acidic hydrogen and is not an acidic salt.

6. **Examining Na3PO4**:
- This salt is derived from H3PO4 (phosphoric acid).
- All three acidic hydrogens are replaced by sodium ions in Na3PO4.
- As a result, there are no acidic hydrogens left, making Na3PO4 not an acidic salt.

7. **Conclusion**:
- Among the given options, only NaH2PO3 retains an acidic hydrogen and is therefore classified as an acidic salt.

### Final Answer:
The acidic salt among the given options is **NaH2PO3**.

---