Which of the following are not amphiprotic in nature?

Options

A. `OH^(-)`
B. `H_(2)PO_(2)^(-)`
C. `HSO_(3)`
D. HF

Answer

To determine which of the given options are not amphiprotic in nature, we need to understand what amphiprotic substances are. Amphiprotic substances can both accept and donate protons (H⁺ ions). Let's analyze each option step by step.

### Step-by-Step Solution:

1. **Understanding Amphiprotic Nature**:
- An amphiprotic substance can act as both an acid (donating H⁺) and a base (accepting H⁺).

2. **Analyzing Option 1: OH⁻ (Hydroxide Ion)**:
- Hydroxide ion (OH⁻) can accept a proton to form water (H₂O).
- However, it cannot donate a proton because it does not have any acidic hydrogen.
- **Conclusion**: OH⁻ is not amphiprotic.

3. **Analyzing Option 2: H₂PO₄⁻ (Dihydrogen Phosphate Ion)**:
- The structure of H₂PO₄⁻ shows that it can accept a proton to form H₃PO₄ (phosphoric acid).
- However, it lacks an acidic hydrogen to donate, meaning it cannot act as a Bronsted acid.
- **Conclusion**: H₂PO₄⁻ is not amphiprotic.

4. **Analyzing Option 3: HSO₃⁻ (Hydrogen Sulfite Ion)**:
- The HSO₃⁻ ion can accept a proton to form H₂SO₃ (sulfurous acid) and can also donate a proton to form SO₃²⁻ (sulfite ion).
- **Conclusion**: HSO₃⁻ is amphiprotic.

5. **Analyzing Option 4: HF (Hydrofluoric Acid)**:
- HF can donate a proton to form F⁻ (fluoride ion).
- However, it cannot accept a proton to form H₂F⁺ because H₂F⁺ is unstable due to the high electronegativity of fluorine.
- **Conclusion**: HF is not amphiprotic.

### Final Answer:
The substances that are **not amphiprotic** are:
- Option 1: OH⁻
- Option 2: H₂PO₄⁻
- Option 4: HF