Which of the following are redox reactions?

Options

A. `Zn+2HClrarrZnCl_(2)+H_(2)`
B. `Al(OH)_(3)+3HClrarrAlCl_(3)+3H_(2)O`
C. `Ag^(o+)+I^(-)rarrAgl`
D. Disproportionation of `Cu^(o+)` in aqueous solution.

Explanation

To determine which of the given reactions are redox reactions, we need to analyze each reaction and identify the changes in oxidation states of the elements involved. A redox reaction involves both oxidation (loss of electrons) and reduction (gain of electrons).

### Step-by-Step Solution:

1. **Identify the Reactions**:
- Reaction A: \( \text{Zn} + 2 \text{HCl} \rightarrow \text{ZnCl}_2 + \text{H}_2 \)
- Reaction B: \( \text{Al(OH)}_3 + 3 \text{HCl} \rightarrow \text{AlCl}_3 + 3 \text{H}_2\text{O} \)
- Reaction C: \( \text{Ag}^+ + \text{I}^- \rightarrow \text{AgI} \)
- Reaction D: \( 2 \text{Cu}^+ \rightarrow \text{Cu}^{2+} + \text{Cu} \)

2. **Analyze Reaction A**:
- Zinc (Zn) is oxidized from 0 to +2 (loses electrons).
- Hydrogen ions (from HCl) are reduced from +1 to 0 (gains electrons).
- **Conclusion**: This is a redox reaction.

3. **Analyze Reaction B**:
- Aluminum (Al) in Al(OH)₃ has an oxidation state of +3 and remains +3 in AlCl₃.
- There is no change in oxidation states.
- **Conclusion**: This is not a redox reaction (only a neutralization reaction).

4. **Analyze Reaction C**:
- Silver (Ag) goes from +1 to 0, and Iodide (I) goes from -1 to 0.
- Both ions are involved in a combination reaction but do not show a change in oxidation states.
- **Conclusion**: This is not a redox reaction.

5. **Analyze Reaction D**:
- Copper (Cu) in Cu⁺ is oxidized to Cu²⁺ (loses electrons).
- The other Cu remains in its elemental form (0 oxidation state).
- **Conclusion**: This is a redox reaction (disproportionation reaction).

6. **Final Conclusion**:
- The reactions that are redox reactions are **A** and **D**.

### Summary:
- **Redox Reactions**: A and D
- **Not Redox Reactions**: B and C