Blister copper is

Options

A. pure copper
B. ore of copper
C. alloy of copper
D. impure copper

Answer

**Step-by-Step Text Solution:**

1. **Definition of Blister Copper:**
Blister copper is an impure form of copper that is produced during the extraction process of copper from its ores.

2. **Extraction Process Overview:**
The extraction of copper involves several steps, including roasting, smelting, and refining. The focus here is on the smelting process that occurs in a Bessemer converter.

3. **Roasting of Sulphide Ore:**
Initially, the copper sulphide ore is roasted. This process converts the sulphide ore into copper oxide while releasing sulfur dioxide (SO2) gas. The chemical reaction can be represented as:
\[ 2Cu_2S + 3O_2 \rightarrow 2Cu_2O + 2SO_2 \]

4. **Smelting Process:**
After roasting, the copper oxide is then smelted in a Bessemer converter. During this process, the copper oxide reacts with oxygen (O2) to produce copper and iron oxide (FeO). The reaction can be represented as:
\[ 2Cu_2O + O_2 \rightarrow 4Cu + 2FeO \]

5. **Formation of Slag:**
Silicon dioxide (SiO2) is added to the mixture to react with the iron oxide (FeO) produced during smelting. This forms a slag (FeSiO3) that is removed from the system. The slag is a waste product that contains impurities.

6. **Formation of Blister Copper:**
As the reaction proceeds, copper begins to deposit in the converter. The presence of dissolved sulfur in the copper forms bubbles as the temperature decreases. These bubbles are visible on the surface of the copper and give it a blistered appearance. This is why it is called blister copper.

7. **Conclusion:**
Blister copper is thus characterized by the presence of these gas bubbles (mostly sulfur) trapped within the copper, making it an impure form of copper.