Which of the following cannot be hydrolysed?

Options

A. A salt of weak acid and strong base
B. A salt of strong acid and weak base
C. A salt of weak acid and weakk base
D. A salt of strong acid and strong base

Answer

To determine which of the following salts cannot be hydrolyzed, we need to analyze each option based on the properties of the acids and bases that form them:

1. **Salt of Weak Acid and Strong Base**: This type of salt can undergo hydrolysis. For example, sodium acetate (from acetic acid and sodium hydroxide) will hydrolyze to produce hydroxide ions, making the solution basic.

2. **Salt of Strong Acid and Weak Base**: This type of salt can also undergo hydrolysis. For instance, ammonium chloride (from hydrochloric acid and ammonium hydroxide) will produce hydrogen ions, making the solution acidic.

3. **Salt of Weak Acid and Weak Base**: This salt can hydrolyze as well, but the extent of hydrolysis will depend on the relative strengths of the weak acid and weak base. For example, ammonium acetate can hydrolyze, but the solution may be neutral depending on the concentrations.

4. **Salt of Strong Acid and Strong Base**: This type of salt cannot be hydrolyzed. For example, sodium chloride (from hydrochloric acid and sodium hydroxide) is formed, and it remains neutral in solution because neither the sodium ion nor the chloride ion reacts with water.

### Conclusion:
The salt that cannot be hydrolyzed is the **salt of strong acid and strong base**. Therefore, the correct answer is option 4.

### Step-by-step Solution:
1. **Identify the types of salts**: List the types of salts provided in the question.
2. **Analyze each salt**:
- Weak Acid + Strong Base: Hydrolyzes to produce a basic solution.
- Strong Acid + Weak Base: Hydrolyzes to produce an acidic solution.
- Weak Acid + Weak Base: Can hydrolyze, but the effect depends on the strengths of the acid and base.
- Strong Acid + Strong Base: Does not hydrolyze; remains neutral.
3. **Determine which salt cannot be hydrolyzed**: Based on the analysis, identify that the salt of strong acid and strong base does not undergo hydrolysis.
4. **Conclude the answer**: State that the correct answer is the salt of strong acid and strong base.