The extraction of `Au` by leaching with `NaCN` both oxidation and reduction. Justify giving equations.

Explanation

To explain the extraction of gold (Au) by leaching with sodium cyanide (NaCN) and to justify that both oxidation and reduction occur, we can break down the process into two main steps, each accompanied by relevant chemical equations.

### Step-by-Step Solution:

**Step 1: Oxidation of Gold**
- In the first step, gold (Au) is oxidized when it reacts with sodium cyanide (NaCN). The gold metal, which has an oxidation state of 0, reacts with cyanide ions (CN⁻) to form a complex ion, [Au(CN)₂]⁻.
- The chemical equation for this reaction can be written as:

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