As the size of gold particle increases the colour of solution varies as

Options

A. Purple blue `rarr` golden `rarr`red
B. Golden`rarr`red `rarr`purple`rarr` blue
C. Red `rarr`purple`rarr` blue`rarr` golden
D. blue `rarr` purple `rarr` golden `rarr` red

Answer

To solve the question regarding the variation of color in a gold colloidal solution as the size of gold particles increases, we can follow these steps:

### Step 1: Understand Colloidal Gold
Colloidal gold consists of tiny particles of gold suspended in a liquid. The size of these particles can affect the color of the solution due to a phenomenon known as surface plasmon resonance.

**Hint:** Consider how the size of particles can interact with light.

### Step 2: Observe Color Changes
As the size of gold particles increases, the color of the solution changes. The typical sequence of colors observed in colloidal gold solutions is:
- Small particles: Red
- Medium particles: Purple
- Larger particles: Blue
- Very large particles: Golden

**Hint:** Think about how different sizes might scatter light differently.

### Step 3: Identify the Color Sequence
Based on the information, we can summarize the color changes as follows:
- **Red**: Small particles (approximately 10-20 nm)
- **Purple**: Medium particles (approximately 20-50 nm)
- **Blue**: Larger particles (approximately 50-100 nm)
- **Golden**: Very large particles (greater than 100 nm)

**Hint:** Remember that the color changes are due to the interaction of light with the particles.

### Step 4: Conclusion
Thus, as the size of the gold particles increases, the color of the solution transitions from red to purple to blue and finally to golden.

**Final Answer:** The correct sequence of color changes as the size of gold particles increases is: Red → Purple → Blue → Golden.

### Summary of Solution Steps:
1. Understand the nature of colloidal gold.
2. Observe the color changes with increasing particle size.
3. Identify the sequence of colors.
4. Conclude the answer based on the observed sequence.