which of the following is a lyophobic colloid ?

Options

A. Gelatin
B. sulphur
C. starch
D. Gum arabic

Answer

To determine which of the following is a lyophobic colloid, we first need to understand the definitions and characteristics of lyophobic and lyophilic colloids.

### Step-by-Step Solution:

1. **Definition of Lyophobic Colloids**:
- Lyophobic colloids are colloidal systems that do not have a strong affinity for the solvent. The term "lyo" means solvent and "phobic" means fearing or repelling. Thus, lyophobic colloids are solvent-repelling.

2. **Characteristics of Lyophobic Colloids**:
- They are thermodynamically unstable.
- They tend to precipitate out of the solution, and this precipitation is an irreversible process.
- There is very little or no attraction between the colloidal particles and the liquid medium.

3. **Examples of Lyophobic Colloids**:
- Common examples of lyophobic colloids include substances like sulfur and certain metal sols.
- In contrast, lyophilic colloids (solvent-loving) include substances like gelatin, starch, and gum arabic.

4. **Identifying the Lyophobic Colloid**:
- From the given options (gelatin, sulfur, starch, gum arabic), we need to identify which one is a lyophobic colloid.
- Gelatin, starch, and gum arabic are examples of lyophilic colloids, while sulfur is a lyophobic colloid.

5. **Conclusion**:
- Therefore, the answer to the question "which of the following is a lyophobic colloid?" is **sulfur**.