Which of the following is the strongest conjugate base ?

Options

A. `Cl^(-)`
B. `CH_(3)COO^(-)`
C. `SO_(4)^(2-)`
D. `NO_(2)^(-)`

Answer

To determine which of the given options is the strongest conjugate base, we need to analyze the acids associated with each conjugate base and identify the weakest acid. The weaker the acid, the stronger its conjugate base will be.

### Step-by-Step Solution:

1. **Identify the Conjugate Bases**:
The given options are:
- Cl⁻ (from HCl)
- CH₃COO⁻ (from CH₃COOH)
- H₂SO₄ (strong acid, not a conjugate base)
- SO₄²⁻ (from H₂SO₄)
- NO₂⁻ (from HNO₂)

2. **Determine the Corresponding Acids**:
- Cl⁻ is the conjugate base of HCl (strong acid).
- CH₃COO⁻ is the conjugate base of CH₃COOH (weak acid).
- H₂SO₄ is a strong acid (not considered here as a conjugate base).
- SO₄²⁻ is the conjugate base of H₂SO₄ (strong acid).
- NO₂⁻ is the conjugate base of HNO₂ (weak acid).

3. **Evaluate the Strength of the Acids**:
- HCl is a strong acid.
- CH₃COOH (acetic acid) is a weak acid.
- H₂SO₄ is a strong acid.
- HNO₂ is a weak acid but stronger than acetic acid.

4. **Identify the Weakest Acid**:
Among the acids, CH₃COOH is the weakest acid compared to HNO₂. Therefore, its conjugate base, CH₃COO⁻, will be the strongest conjugate base.

5. **Conclusion**:
The strongest conjugate base among the options provided is **CH₃COO⁻** (from acetic acid).

### Final Answer:
The strongest conjugate base is **CH₃COO⁻** (from acetic acid).