Which of the following will give respective metal by self reduction ?

Options

A. Galena PbS
B. HgS
C. ZnS
D. Both (1) &(2)

Answer

To solve the question "Which of the following will give respective metal by self-reduction?", we need to analyze the given options and understand the concept of self-reduction (or auto-reduction).

### Step-by-Step Solution:

1. **Understand Self-Reduction**:
- Self-reduction refers to the process where certain metal ores can reduce themselves to their respective metals without the need for an external reducing agent. This typically occurs when the ore is heated in the presence of air.

2. **Identify the Ores**:
- The options given are:
1. Galena (PbS)
2. Mercury Sulfide (HgS)
3. Zinc Sulfide (ZnS)
4. Both 1 and 2

3. **Analyze Galena (PbS)**:
- When Galena (PbS) is heated in air, it reacts with oxygen to form Lead Oxide (PbO) and Sulfur Dioxide (SO2):
\[ 2 \text{PbS} + 3 \text{O}_2 \rightarrow 2 \text{PbO} + 2 \text{SO}_2 \]
- The Lead Oxide can then react with the remaining Lead Sulfide to yield Lead (Pb) and more Sulfur Dioxide:
\[ \text{PbS} + \text{PbO} \rightarrow 2 \text{Pb} + \text{SO}_2 \]
- Thus, Galena can give Lead by self-reduction.

4. **Analyze Mercury Sulfide (HgS)**:
- When Mercury Sulfide (HgS) is heated in air, it also reacts with oxygen to form Mercury Oxide (HgO) and Sulfur Dioxide:
\[ 2 \text{HgS} + 3 \text{O}_2 \rightarrow 2 \text{HgO} + 2 \text{SO}_2 \]
- The Mercury Oxide can then react with the remaining Mercury Sulfide to yield Mercury (Hg) and Sulfur Dioxide:
\[ \text{HgS} + \text{HgO} \rightarrow 2 \text{Hg} + \text{SO}_2 \]
- Therefore, Mercury Sulfide can also give Mercury by self-reduction.

5. **Analyze Zinc Sulfide (ZnS)**:
- Zinc Sulfide (ZnS) does not undergo self-reduction. It requires an external reducing agent for the reduction to Zinc (Zn).

6. **Conclusion**:
- Since both Galena (PbS) and Mercury Sulfide (HgS) can give their respective metals through self-reduction, the correct answer is:
- **Option 4: Both 1 and 2**.