Main ore of lead is gaalena.This is mined and separated from other minerals by froth flotation.There are two methods of extracting the lead.
(i)First method involves the roasting of ore followed by
reduction with coke or CO.
(ii)Second method involves the partial roasting of ore followed by
self reduction.
In self reduction process, the species which bring about the
reduction is :

Options

A. `O_2`
B. `S^(2-)`
C. `O^(2-)`
D. `H_2S`

Explanation

To solve the question regarding the self-reduction process of lead extraction from galena (PbS), we will follow these steps:

### Step-by-Step Solution:

1. **Identify the Ore and Its Composition**:
- The main ore of lead is galena, which is primarily composed of lead sulfide (PbS).

2. **Understand the Extraction Methods**:
- There are two methods mentioned for extracting lead from galena:
- **First Method**: Roasting of the ore followed by reduction with coke (C) or carbon monoxide (CO).
- **Second Method**: Partial roasting of the ore followed by self-reduction.

3. **Analyze the Self-Reduction Process**:
- In the self-reduction process, the lead sulfide (PbS) is partially roasted, which means it is oxidized to lead oxide (PbO) and sulfur dioxide (SO2).
- The reaction can be represented as:
\[ 2 \text{PbS} + 3 \text{O}_2 \rightarrow 2 \text{PbO} + 2 \text{SO}_2 \]

4. **Identify the Species Involved in Self-Reduction**:
- After partial roasting, some PbS remains along with the PbO formed.
- The self-reduction occurs when PbO reacts with the remaining PbS:
\[ \text{PbO} + \text{PbS} \rightarrow \text{Pb} + \text{SO}_2 \]
- In this reaction, PbS acts as a reducing agent because it provides electrons to reduce PbO to lead (Pb).

5. **Determine the Reducing Agent**:
- The species that brings about the reduction in this process is the sulfide ion (S^2-), which is present in PbS.
- Therefore, the reducing agent in the self-reduction process is the sulfide ion (S^2-).

### Final Answer:
The species which brings about the reduction in the self-reduction process is **S^2- (sulfide ion)**.

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