Which of the following statement is true

Options

A. The conjugate base of a strong acid is a strong base
B. The conjugate base of a acid acid is a strong base
C. The conjugate base of a acid acid is a weak base
D. The base and its conjugate acid react to form a neutral solution

Explanation

To determine which statement is true regarding conjugate acids and bases, we need to analyze the properties of strong and weak acids and their conjugate bases.

### Step-by-Step Solution:

1. **Understanding Strong Acids and Their Conjugate Bases**:
- Strong acids completely dissociate in water. For example, hydrochloric acid (HCl) dissociates completely into H⁺ and Cl⁻ ions.
- The conjugate base of a strong acid is the species that remains after the acid donates a proton. In the case of HCl, the conjugate base is Cl⁻.

2. **Properties of Conjugate Bases**:
- The conjugate base of a strong acid is weak. This is because strong acids have a strong tendency to donate protons, and thus their conjugate bases have little tendency to accept protons.
- For example, Cl⁻ is a weak base and does not significantly react with water to form OH⁻ ions.

3. **Analyzing the Options**:
- **Option 1**: "The conjugate base of a strong acid is a strong base." This is false because we just established that the conjugate base of a strong acid is weak.
- **Option 2**: "The conjugate base of an acid is a strong base." This is ambiguous and does not specify whether the acid is strong or weak. However, it is generally incorrect because the conjugate base of a strong acid is weak.
- **Option 3**: "The conjugate base of a weak acid is a strong base." This is also false because the conjugate base of a weak acid is typically a weak base.
- **Option 4**: "The conjugate base of a weak acid is a weak base." This is true because the conjugate base of a weak acid does not have a strong tendency to accept protons.

4. **Conclusion**:
- The only true statement among the options provided is that the conjugate base of a weak acid is a weak base.

### Final Answer:
The true statement is: "The conjugate base of a weak acid is a weak base."