Which of the following change represents a disproportionation reaction (s) :

Options

A. `Cl_2 + 2OH^- to CIO^(-) + Cl^(-) + H_2O`
B. `Cu_2O + 2H^+ to Cu + Cu^(2+) + H_2O`
C. `2HCuCl_2 overset("Dilution with")(rarr) Cu + Cu^(2+) + 4Cl^(-) + 2H^(+)`
D. All of these

Answer

To determine which of the following changes represents a disproportionation reaction, we need to understand the definition of a disproportionation reaction. A disproportionation reaction is a specific type of redox reaction where a single species is simultaneously oxidized and reduced, resulting in two different products.

Let's analyze the provided reactions step by step:

1. **Identify the reactions**: We are given several reactions to analyze. We need to check the oxidation states of the elements involved in each reaction.

2. **Analyze the first reaction**:
- **Reaction**: Cl₂ + 2H⁻ → Cl⁻ + Cl⁻ + H₂O
- **Oxidation states**: Cl in Cl₂ is 0, in Cl⁻ is -1. Here, Cl is reduced (0 to -1) and oxidized (0 to +1 in H₂O).
- **Conclusion**: This is a disproportionation reaction.

3. **Analyze the second reaction**:
- **Reaction**: Cu₂O + 2S²⁺ → Cu + Cu²⁺ + S₂O
- **Oxidation states**: Cu in Cu₂O is +1, in Cu is 0, and in Cu²⁺ is +2. Here, Cu is reduced (from +1 to 0) and oxidized (from +1 to +2).
- **Conclusion**: This is also a disproportionation reaction.

4. **Analyze the third reaction**:
- **Reaction**: 2CuCl₂ → Cu + Cu²⁺ + 4Cl⁻ + 2H⁺
- **Oxidation states**: Cu in CuCl₂ is +2, in Cu is 0, and in Cu²⁺ is +2. Here, Cu is reduced (from +2 to 0) and oxidized (from +2 to +2).
- **Conclusion**: This is a disproportionation reaction as well.

5. **Final conclusion**: All the reactions provided represent disproportionation reactions.

Thus, the correct answer is that all the reactions are disproportionation reactions.

### Summary of Steps:
1. Understand the definition of disproportionation reactions.
2. Analyze the oxidation states in each reaction.
3. Determine if the species is both oxidized and reduced in the reaction.
4. Conclude which reactions are disproportionation reactions.