What is meant by self-reduction process?

Explanation

### Step-by-Step Text Solution

1. **Definition of Self-Reduction**: Self-reduction is a process in which a metal reduces itself from a higher oxidation state to a lower oxidation state, ultimately forming the crude metal.

2. **Example of Copper**: A common example of self-reduction can be observed in the extraction of copper from its sulfide ore, specifically copper(I) sulfide (Cu₂S).

3. **Initial Reaction**: In the process of extracting copper, the copper sulfide is partially converted into copper oxide (Cu₂O) in a reaction that releases sulfur dioxide (SO₂). This occurs in a process called roasting.

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