Solidified Cu obtained from the reverberatory furnace has blistered appearance. This is due to

Options

A. Evolution of `CO_2` gas
B. Evolution of `SO_2` gas
C. Due to evaporation of volatile materials
D. Evolution of `NO_2`

Answer

### Step-by-Step Solution:

1. **Understanding the Process**: The question pertains to the solidification of copper obtained from a reverberatory furnace. In this process, copper oxide (Cu2O) reacts with copper sulfide (Cu2S).

2. **Identifying the Reaction**: The chemical reaction that occurs in the reverberatory furnace can be represented as:
\[ \text{Cu}_2\text{S} + \text{Cu}_2\text{O} \rightarrow 4\text{Cu} + \text{SO}_2 \]
Here, copper sulfide and copper oxide react to produce copper and sulfur dioxide (SO2).

3. **Analyzing the Byproduct**: During the reaction, sulfur dioxide (SO2) is released as a gas. This gas forms bubbles in the molten copper as it solidifies.

4. **Formation of Blisters**: The blistered appearance of solidified copper is due to the trapped sulfur dioxide gas that forms bubbles in the solid copper. As the copper solidifies, these bubbles create a blistered texture.

5. **Conclusion**: Therefore, the blistered appearance of solidified copper obtained from the reverberatory furnace is due to the evolution of sulfur dioxide gas during the reaction.

### Final Answer:
The solidified copper obtained from the reverberatory furnace has a blistered appearance due to the evolution of sulfur dioxide (SO2) gas during the reduction process.

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