Blister copper is

Options

A. 1. impure copper
B. 2. obtained in self-reduction process during bessemerisation
C. 3. both are correct
D. 4. none is correct

Explanation

**Step-by-Step Solution:**

1. **Understanding Blister Copper:**
Blister copper is a term used to describe a specific form of copper that is produced during the extraction process from copper sulfide ores. It is characterized by the presence of gas bubbles or "blisters" on its surface.

2. **Extraction Process:**
The extraction of copper from copper sulfide ore involves a process called partial roasting. In this process, copper sulfide (Cu₂S) is partially oxidized in the presence of oxygen.

**Reaction:**
\[ 2Cu_2S + 3O_2 \rightarrow 2Cu_2O + 2SO_2 \]

3. **Auto-Reduction:**
The copper(I) oxide (Cu₂O) produced from the partial roasting undergoes a further reaction known as auto-reduction. This occurs in the presence of excess copper(I) sulfide (Cu₂S).

**Reaction:**
\[ Cu_2O + Cu_2S \rightarrow 4Cu + SO_2 \]

4. **Formation of Blister Copper:**
The result of these reactions is the formation of blister copper, which is approximately 97-98% pure copper. The remaining 1-3% consists mainly of sulfur that gets trapped in the form of bubbles (blisters) within the copper.

5. **Purity of Blister Copper:**
Blister copper is not completely pure due to the presence of sulfur impurities. Therefore, it is essential to further refine blister copper to obtain pure copper.

6. **Conclusion:**
Based on the above information, blister copper can be defined as impure copper that contains trapped sulfur, produced during the extraction of copper from copper sulfide ores through partial roasting and auto-reduction.

**Final Answer:**
Blister copper is impure copper that contains trapped sulfur.

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