Lyophobic colloids

Options

A. May be prepared by simply mixing metals with
dispersion medium
B. Are reversible solutions
C. Cannot be easily coagulated
D. Need stabilising agents for their preservation

Answer

### Step-by-Step Solution for the Question on Lyophobic Colloids

**Step 1: Understanding Lyophobic Colloids**
- Lyophobic colloids are colloidal systems where there is little to no affinity between the dispersed phase (the particles) and the dispersion medium (the liquid). This lack of affinity means that the particles do not easily mix or interact with the medium.

**Step 2: Characteristics of Lyophobic Colloids**
- These colloids are typically unstable and can be easily coagulated or precipitated. Coagulation can occur through the addition of small amounts of electrolytes, heating, or shaking.

**Step 3: Formation of Lyophobic Colloids**
- Lyophobic colloids cannot be formed simply by mixing the dispersed phase with the dispersion medium. Instead, they require specific methods for their preparation, such as chemical reactions or other specialized techniques.

**Step 4: Stability and Preservation**
- Due to their instability, lyophobic colloids require stabilizing agents to maintain their colloidal state. These stabilizers help to prevent the particles from aggregating and settling out of the dispersion.

**Step 5: Evaluating the Options**
- Now, let's evaluate the provided options:
1. **May be prepared by simply mixing metals with dispersion medium**: This is incorrect. Lyophobic colloids require special methods for preparation.
2. **Are reversible solutions**: This is incorrect. Lyophobic colloids are irreversible; once formed, they cannot be reverted back to their original state easily.
3. **Cannot be easily coagulated**: This is incorrect. They can be easily coagulated by adding electrolytes or through heating/shaking.
4. **Need stabilizing agents for their preservation**: This is correct. Lyophobic colloids are unstable and require stabilizers to maintain their colloidal state.

**Conclusion:**
- The correct answer is **D: Need stabilizing agents for their preservation**.