Which of the following is/are lyphobic colloids?

Options

A. gold sol
B. `As_(2)S_(3)` sol
C. `Fe(OH)_(3)` sol
D. Starch sol

Answer

To determine which of the given colloids are lyophobic, we first need to understand the definitions and characteristics of lyophilic and lyophobic colloids.

### Step-by-Step Solution:

1. **Understanding Colloids**:
- Colloids are mixtures where one substance is dispersed evenly throughout another. They can be classified into two main types: lyophilic and lyophobic colloids.

2. **Lyophilic Colloids**:
- Lyophilic colloids have a strong affinity for the solvent. They are stable and can easily be formed by mixing the solute with the solvent. Examples include starch, gelatin, glue, gum, rubber, and proteins.

3. **Lyophobic Colloids**:
- Lyophobic colloids have little to no affinity for the solvent. They are less stable and require special methods for their formation. Examples include colloids formed from metals (like gold and silver), metal hydroxides (like aluminum hydroxide and iron hydroxide), and metal sulfides (like arsenic sulfide).

4. **Identifying Lyophobic Colloids**:
- Given the examples, we need to identify which of the following are lyophobic:
- Gold sol (lyophobic)
- Arsenic sol (lyophobic)
- Iron hydroxide (lyophobic)
- Starch sol (lyophilic)

5. **Conclusion**:
- The lyophobic colloids from the options provided are:
- Gold sol
- Arsenic sol
- Iron hydroxide

- Starch sol is a lyophilic colloid and is therefore not included in the lyophobic category.

### Final Answer:
The lyophobic colloids from the options provided are:
- Gold sol
- Arsenic sol
- Iron hydroxide