The compound `Ba_(2)Cu_(3)O_(7)`, which shows super conductivity, has copper in oxidation state ......... Assume that the rare earth element yttrium is in its usual +3 oxidation state.

Explanation

To determine the oxidation state of copper in the compound \( Ba_2Cu_3O_7 \), we can follow these steps:

### Step 1: Identify the oxidation states of known elements
- Yttrium (Y) is in its usual +3 oxidation state.
- Barium (Ba) is an alkaline earth metal (Group 2) and has an oxidation state of +2.
- Oxygen (O) typically has an oxidation state of -2.

### Step 2: Write the equation based on the oxidation states
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