An ore on treatment with dilute hydrochloric acid gives a smell of rotten eggs. Which of the following processes can be used to obtain pure metal from the concentrated form of this ore?

Options

A. Roasting followed by reduction with carbon.
B. Calcination followed by electrolytic reduction.
C. Roasting followed by heating.
D. Both (A) and (C)

Explanation

To solve the question, we need to analyze the information provided and determine the correct processes to obtain pure metal from the concentrated form of the ore that gives off a smell of rotten eggs when treated with dilute hydrochloric acid.

### Step-by-Step Solution:

1. **Identify the Ore**:
- The question states that the ore gives off a smell of rotten eggs when treated with dilute hydrochloric acid. The smell of rotten eggs is characteristic of hydrogen sulfide (H₂S), which indicates that the ore is likely a sulfide ore (e.g., zinc sulfide, ZnS).

2. **Understanding the Treatment with Dilute Hydrochloric Acid**:
- When a sulfide ore reacts with dilute hydrochloric acid, it produces hydrogen sulfide gas. This reaction can be represented as:
\[ \text{ZnS} + 2 \text{HCl} \rightarrow \text{ZnCl}_2 + \text{H}_2\text{S} \]
- This confirms that the ore is a sulfide and we need to convert it into a more usable form for metal extraction.

3. **Concentration of the Ore**:
- The first step in extracting metal from sulfide ores is to convert the sulfide into an oxide. This is typically done by a process called roasting, where the ore is heated in the presence of oxygen:
\[ \text{2 ZnS} + \text{3 O}_2 \rightarrow \text{2 ZnO} + \text{2 SO}_2 \]
- This process converts zinc sulfide (ZnS) into zinc oxide (ZnO) and sulfur dioxide (SO₂).

4. **Reduction of the Oxide**:
- After obtaining the oxide, the next step is to reduce the zinc oxide to pure zinc metal. This can be done by heating zinc oxide with carbon:
\[ \text{ZnO} + \text{C} \rightarrow \text{Zn} + \text{CO} \]
- This reduction process allows us to obtain the pure metal.

5. **Evaluating the Options**:
- Based on the processes described:
- **Roasting followed by reduction with carbon** is a valid method (Option A).
- **Calcination followed by electrolytic reduction** is incorrect because calcination is performed in the absence of oxygen and does not apply here (Option B).
- **Roasting followed by heating** is also a valid method (Option C).
- Therefore, both Option A and Option C are correct processes.

6. **Conclusion**:
- The correct answer to the question is **Option 4: Both A and C**.