Colloidal solution of gold prepared by different methods have different colours, because 

Options

A. variable valencies of gold
B. difference in the concentration of gold particles
C. impurities produced by different methods
D. difference in the diameter of colloidal gold particles

Answer

To solve the question regarding why colloidal solutions of gold prepared by different methods have different colors, we can break down the explanation into clear steps:

### Step-by-Step Solution:

1. **Understanding Colloidal Solutions**:
- A colloidal solution consists of tiny particles (the dispersed phase) suspended in a medium (the dispersion medium). In this case, we are dealing with gold particles suspended in a liquid.

2. **Factors Affecting Color**:
- The color of colloidal solutions is influenced by several factors, including the size of the particles in the dispersed phase.

3. **Particle Size and Color Relationship**:
- The size of the gold nanoparticles can vary depending on the method used to prepare the colloidal solution. Smaller particles tend to scatter light differently than larger particles.

4. **Light Scattering**:
- When light interacts with the colloidal particles, it can be scattered in various ways. The wavelength of light that is scattered depends on the size of the particles. Smaller particles scatter shorter wavelengths (blue light), while larger particles scatter longer wavelengths (red light).

5. **Conclusion**:
- Therefore, the different colors observed in colloidal solutions of gold prepared by different methods can be attributed to the difference in the diameter of the colloidal gold particles. This difference in size leads to variations in light scattering, resulting in different colors.

### Final Answer:
The colloidal solution of gold prepared by different methods has different colors because of the difference in the diameter of colloidal gold particles.

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