Explain how the colour of `K_2Cr_2O_7` solution depends on pH of the solution.

Explanation

To explain how the color of \( K_2Cr_2O_7 \) (potassium dichromate) solution depends on the pH of the solution, we need to understand the behavior of dichromate ions (\( Cr_2O_7^{2-} \)) and chromate ions (\( CrO_4^{2-} \)) in different pH environments.

### Step-by-Step Solution:

1. **Identify the Species**:
- Potassium dichromate contains the dichromate ion \( Cr_2O_7^{2-} \). In acidic solutions, this ion is predominant.

2. **Color in Acidic Medium**:
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