Which one of the following statements is not correct?

Options

A. Lyophilic sols have higher viscosity than the medium
B. Much larger quantities of electrolytes are needed to cause precipitation of lyophilic sols
C. Lyophobic sols are reversible
D. The particles of lyophilic sols are highly hydrated

Answer

To determine which statement is not correct regarding lyophilic and lyophobic sols, let's analyze each statement step by step.

### Step 1: Understand Lyophilic and Lyophobic Sols
- **Lyophilic Sols**: These are colloidal systems where the dispersed phase has a strong affinity for the dispersion medium. They are stable and can easily be re-dispersed after precipitation.
- **Lyophobic Sols**: These are colloidal systems where the dispersed phase has little to no affinity for the dispersion medium. They are less stable and tend to precipitate easily.

### Step 2: Analyze Each Statement
1. **Statement 1**: "Lyophilic sols have higher viscosity than the medium."
- **Analysis**: This statement is correct. Lyophilic sols have a protective layer that increases their viscosity compared to the dispersion medium.

2. **Statement 2**: "Much larger quantities of electrolytes are needed to cause precipitation of lyophilic sol."
- **Analysis**: This statement is also correct. Lyophilic sols require a significant amount of electrolytes to overcome the protective layer and cause coagulation.

3. **Statement 3**: "Lyophobic sols are reversible."
- **Analysis**: This statement is incorrect. Lyophobic sols are generally irreversible. Once they precipitate, they cannot easily be re-dispersed without significant effort.

4. **Statement 4**: "The particles of lyophilic sols are highly hydrated."
- **Analysis**: This statement is correct. The strong affinity of lyophilic particles for the dispersion medium leads to a high degree of hydration.

### Conclusion
The statement that is not correct is **Statement 3**: "Lyophobic sols are reversible."