Classify Na{{H}_{2}}P{{O}_{2}} and NaHS{{O}_{4}} salts as acid salt or normal salt.

To classify the salts Na₂HPO₂ and NaHSO₄ as either acid salts or normal salts, let’s first understand what these terms mean:

1. **Acid Salt**: An acid salt is a salt that still contains replaceable hydrogen ions (H⁺) in its structure. These salts are derived from a diprotic or polyprotic acid where not all of the hydrogen ions have been replaced by a metal ion.

2. **Normal Salt**: A normal salt is formed when all the replaceable hydrogen ions in the acid have been replaced by metal ions, resulting in no remaining hydrogen ions in the salt.

Now, let’s analyze each salt:

1. **Na₂HPO₂**:
- Sodium hypophosphite (Na₂HPO₂) is derived from hypophosphorous acid (H₃PO₂).
- Hypophosphorous acid is a monoprotic acid (one acidic hydrogen ion). When it loses one hydrogen ion, it forms the hypophosphite ion (HPO₂²⁻).
- Sodium hypophosphite (Na₂HPO₂) has one replaceable hydrogen ion (HPO₂²⁻), meaning it is an acid salt because it can still donate a hydrogen ion.

2. **NaHSO₄**:
- Sodium bisulfate (NaHSO₄) is derived from sulfuric acid (H₂SO₄).
- Sulfuric acid is a diprotic acid (two acidic hydrogen ions). When it loses one hydrogen ion, it forms the hydrogen sulfate ion (HSO₄⁻).
- Sodium bisulfate (NaHSO₄) still has one replaceable hydrogen ion (HSO₄⁻), making it an acid salt because it retains one hydrogen ion that can be replaced.

**Summary**:
- **Na₂HPO₂** (Sodium hypophosphite) is an **acid salt**.
- **NaHSO₄** (Sodium bisulfate) is also an **acid salt**.