In the extraction of copper when molten copper is cooled slowly, blister copper is obtained due to evolution of the following gas

Options

A. Water vapour
B. Sulphur dioxide
C. Carbon dioxide
D. Carbon monoxide

Answer

To answer the question regarding the evolution of gas during the extraction of copper that leads to the formation of blister copper, we can follow these steps:

### Step 1: Understand the Process of Copper Extraction
Copper is extracted from its ores through various methods, including smelting. During smelting, copper ores are heated in the presence of a reducing agent, which helps in separating copper from its ore.

**Hint:** Research the basic steps involved in the extraction of copper from its ores.

### Step 2: Identify the Form of Copper Obtained
When molten copper is cooled slowly, it solidifies and can form a structure known as "blister copper." This form of copper contains small gas bubbles or "blisters" on its surface.

**Hint:** Look into the characteristics of blister copper and how it differs from pure copper.

### Step 3: Determine the Gas Involved
The gas that is evolved during the cooling of molten copper is primarily **sulfur dioxide (SO₂)**. This gas is produced from the oxidation of sulfur present in the copper ores during the smelting process.

**Hint:** Investigate the chemical reactions that occur during the smelting of copper ores, particularly focusing on sulfur compounds.

### Step 4: Conclusion
Thus, the evolution of sulfur dioxide gas during the cooling of molten copper leads to the formation of blister copper.

**Final Answer:** The gas evolved during the extraction of copper that results in blister copper is sulfur dioxide (SO₂).