Which is the set of amphiprotic species?

Options

A. `H_(3)O^(+),HPO_(4)^(2-),HCO_(3)^(-)`
B. `H_(2)O,HPO_(3)^(2-),H_(2)PO_(2)^(-)`
C. `H_(2)PO_(4)^(-),H_(2)PO_(3)^(-),H_(2)O`
D. All of these

Answer

To determine which set contains only amphiprotic species, we need to understand the definition of amphiprotic species. Amphiprotic species are those that can both donate and accept protons (H⁺ ions), meaning they can act as both acids and bases.

### Step-by-Step Solution:

1. **Identify the Sets**: We need to analyze the given sets of species to determine which ones are amphiprotic.

2. **Examine the First Set**:
- **Set 1**: H₃O⁺, HPO₄²⁻, HCO₃⁻
- **H₃O⁺ (Hydronium ion)**:
- Can donate H⁺ to form water (H₂O) → acts as an acid.
- Cannot accept H⁺ → does not act as a base.
- **Conclusion**: H₃O⁺ is not amphiprotic.
- Since one species is not amphiprotic, this entire set cannot be amphiprotic.

3. **Examine the Second Set**:
- **Set 2**: H₂O, HPO₃²⁻, H₂PO₂⁻
- **H₂O (Water)**:
- Can donate H⁺ to form OH⁻ → acts as an acid.
- Can accept H⁺ to form H₃O⁺ → acts as a base.
- **Conclusion**: H₂O is amphiprotic.
- **HPO₃²⁻**:
- Can accept H⁺ to form H₂PO₃⁻ → acts as a base.
- Cannot donate H⁺ → does not act as an acid.
- **Conclusion**: HPO₃²⁻ is not amphiprotic.
- Since one species is not amphiprotic, this entire set cannot be amphiprotic.

4. **Examine the Third Set**:
- **Set 3**: H₂PO₄⁻, H₂PO₃⁻, H₂O
- **H₂PO₄⁻**:
- Can donate H⁺ to form HPO₄²⁻ → acts as an acid.
- Can accept H⁺ to form H₃PO₄ → acts as a base.
- **Conclusion**: H₂PO₄⁻ is amphiprotic.
- **H₂PO₃⁻**:
- Can donate H⁺ to form HPO₃²⁻ → acts as an acid.
- Can accept H⁺ to form H₃PO₃ → acts as a base.
- **Conclusion**: H₂PO₃⁻ is amphiprotic.
- **H₂O**:
- As previously established, H₂O is amphiprotic.
- **Conclusion**: All three species in this set (H₂PO₄⁻, H₂PO₃⁻, H₂O) are amphiprotic.

5. **Final Conclusion**: The correct set of amphiprotic species is **Set 3**: H₂PO₄⁻, H₂PO₃⁻, H₂O.