BRONSTED LOWRY ACIDS AND BASES

Options

A. `H_(2)`
B. `HCO_(3)^(-)`
C. `NH_(3)`
D. `NH_(2)^(-)`

Explanation

### Step-by-Step Solution:

1. **Understanding Bronsted-Lowry Theory**:
- According to the Bronsted-Lowry theory, an acid is defined as a substance that donates protons (H⁺ ions), while a base is defined as a substance that accepts protons.

2. **Analyzing the Options**:
- We will evaluate each option to determine whether it acts as a Bronsted-Lowry acid, a Bronsted-Lowry base, or neither.

3. **Option 1: H₂**:
- H₂ (hydrogen gas) does not have the ability to donate or accept protons. Therefore, it is neither an acid nor a base.
- **Conclusion**: This option is incorrect.

4. **Option 2: HCO₃⁻ (bicarbonate ion)**:
- HCO₃⁻ can act as a Bronsted-Lowry acid by donating a proton to form CO₃²⁻ (carbonate ion).
- It can also act as a Bronsted-Lowry base by accepting a proton to form H₂CO₃ (carbonic acid).
- **Conclusion**: Since HCO₃⁻ can both donate and accept protons, it is amphoteric and acts as both a Bronsted acid and a Bronsted base. This option is correct.

5. **Option 3: NH₃ (ammonia)**:
- NH₃ can accept a proton to form NH₄⁺ (ammonium ion). Thus, it acts solely as a Bronsted-Lowry base.
- **Conclusion**: This option is incorrect as it does not act as an acid.

6. **Option 4: NH₂⁻ (amide ion)**:
- NH₂⁻ can accept a proton to form NH₃. It acts as a Bronsted-Lowry base.
- **Conclusion**: This option is also incorrect as it does not act as an acid.

7. **Final Conclusion**:
- The only correct option that can act as both a Bronsted-Lowry acid and base is HCO₃⁻.

### Final Answer:
- The correct answer is **Option 2: HCO₃⁻**.