Which of the following is not an acidic salt ?

Options

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

Answer

To determine which of the given salts is not an acidic salt, we need to analyze each option based on the definitions of acidic salts. An acidic salt is typically defined as a salt that contains one or more replaceable hydrogen ions (H⁺) or is formed from a strong acid and a weak base.

### Step-by-Step Solution:

1. **Understand the Definitions**:
- An acidic salt contains one or more replaceable hydrogen ions.
- It can also be formed from a strong acid and a weak base.

2. **Analyze Each Option**:
- **Option A: NaH2PO2**
- The anion is H2PO2⁻.
- Structure: P=O, OH, H, O⁻.
- There are no replaceable acidic hydrogens in this structure.
- Conclusion: NaH2PO2 is **not an acidic salt**; it is a basic salt.

- **Option B: NaH2PO3**
- The anion is H2PO3⁻.
- Structure: P=O, OH, O⁻, H.
- There is one replaceable acidic hydrogen (the one attached to the oxygen).
- Conclusion: NaH2PO3 is an **acidic salt**.

- **Option C: NaH2PO4**
- The anion is H2PO4⁻.
- Structure: P=O, OH, OH, O⁻.
- There are two replaceable acidic hydrogens in this structure.
- Conclusion: NaH2PO4 is an **acidic salt**.

- **Option D: Na2HPO4**
- The anion is HPO4²⁻.
- Structure: P=O, OH, O⁻, O⁻.
- There is one replaceable acidic hydrogen in this structure.
- Conclusion: Na2HPO4 is also an **acidic salt**.

3. **Final Conclusion**:
- The only salt that is not acidic is **NaH2PO2** (Option A).

### Summary:
The salt that is not an acidic salt among the options provided is **NaH2PO2**.