Collidal solutios of gold prepared by different methods are of different colours because of

Options

A. Different diameters of colloidal gold particles
B. Variable valency of gold
C. Different concentrations of gold particles
D. Impurites produced by different methods

Answer

To solve the question regarding why colloidal solutions of gold prepared by different methods exhibit different colors, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Colloidal Solutions**:
- Colloidal solutions consist of small particles dispersed throughout a medium. In the case of gold colloids, these particles are tiny gold nanoparticles.

2. **Tyndall Effect**:
- Colloids exhibit a phenomenon known as the Tyndall effect, where light is scattered by the colloidal particles. This scattering is responsible for the visibility of the colloidal solution.

3. **Dependence on Particle Size**:
- The color observed in a colloidal solution is influenced by the size (diameter) of the colloidal particles. Different sizes of particles will scatter light differently.

4. **Scattering of Light**:
- The scattering of light by the colloidal particles depends on their size relative to the wavelength of light. Smaller particles scatter shorter wavelengths (blue light) more effectively, while larger particles scatter longer wavelengths (red light) more effectively.

5. **Different Methods of Preparation**:
- Different methods of preparing colloidal gold can lead to variations in the size of the gold nanoparticles. For example, chemical reduction methods, electrochemical methods, or physical methods can yield particles of different sizes.

6. **Conclusion**:
- Since the color of the colloidal gold solution is a result of the scattering of light by the particles, and since the size of these particles varies with the method of preparation, the different colors observed in colloidal solutions of gold are due to the different diameters of the gold particles.

### Final Answer:
The different colors of colloidal solutions of gold prepared by different methods are due to the different diameters of the gold particles.