An example of micelle is:

Options

A. Sodium stearate
B. Gold sol.
C. Solution of NaCl
D. Ruby glass.

Answer

To determine an example of a micelle, we need to understand what micelles are and the characteristics of the options provided.

### Step-by-Step Solution:

1. **Understanding Micelles**:
- Micelles are formed by the aggregation of surfactant molecules in a solution when the concentration exceeds a certain threshold known as the Critical Micelle Concentration (CMC).
- They consist of a hydrophilic (water-attracting) head and a hydrophobic (water-repelling) tail. In aqueous solutions, the hydrophobic tails aggregate to minimize their exposure to water, while the hydrophilic heads remain in contact with the water.

2. **Identifying Associated Colloids**:
- Micelles are a type of associated colloid. They typically form from surfactants, which are compounds that lower the surface tension between two substances, such as oil and water.

3. **Evaluating the Options**:
- **Sodium Stearate**: This is a surfactant and is known to form micelles in solution. It has a long hydrocarbon chain (the hydrophobic tail) and a carboxylate group (the hydrophilic head).
- **Gold Salt**: This is not a surfactant and does not form micelles. It is a colloidal solution of gold particles.
- **Solution of NaCl**: Sodium chloride (NaCl) is an ionic compound that dissociates into Na+ and Cl- ions in solution, but it does not form micelles.
- **Ruby Glass**: This is a type of glass that contains gold or other metal oxides, but it is not a colloid and does not form micelles.

4. **Conclusion**:
- Among the options provided, **Sodium Stearate** is the only compound that fits the definition of a micelle as it can form micelles in solution due to its surfactant properties.

### Final Answer:
An example of micelle is **Sodium Stearate**.