Why is `Cu^(+)` ion not stable in aqueous solution ?
or
Why is `Cu^(+)` is not known in aqueous solution ?

Explanation

### Step-by-Step Solution

1. **Understanding the Copper Ion**:
- Copper can exist in multiple oxidation states, primarily +1 (Cu⁺) and +2 (Cu²⁺). The stability of these ions in aqueous solution varies.

2. **Disproportionation Reaction**:
- The term "disproportionation" refers to a reaction where a single species is simultaneously oxidized and reduced. In the case of Cu⁺, it can disproportionate into Cu²⁺ and Cu (metallic copper).
- The reaction can be represented as:
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