The addition of silica during the extraction of copper from its sulphide ore :-

Options

A. converts copper sulphide into copper silicate
B. converts iron oxide into iron silicate
C. reduces copper sulphide into metallic copper
D. reduces the melting point of the reaction mixture

Answer

**Step-by-Step Solution:**

1. **Understanding the Process:**
The extraction of copper from its sulfide ore involves roasting the ore to convert it into oxides. The primary sulfide ore of copper is chalcopyrite (CuFeS₂), which is roasted in the presence of oxygen.

2. **Roasting Reaction:**
During roasting, the copper sulfide (Cu₂S) reacts with oxygen (O₂) to form copper(I) oxide (Cu₂O) and sulfur dioxide (SO₂). The iron sulfide (FeS) also reacts with oxygen to form iron(II) oxide (FeO) and sulfur dioxide (SO₂).
- For copper:
\[ 2 \text{Cu}_2\text{S} + 3 \text{O}_2 \rightarrow 4 \text{Cu}_2\text{O} + 2 \text{SO}_2 \]
- For iron:
\[ 2 \text{FeS} + 3 \text{O}_2 \rightarrow 2 \text{FeO} + 2 \text{SO}_2 \]

3. **Role of Silica (SiO₂):**
After roasting, silica (SiO₂) is added to the mixture in the reverberatory furnace. The primary role of silica is to react with the iron(II) oxide (FeO) formed during roasting.

4. **Formation of Slag:**
The reaction between silica and iron(II) oxide produces iron silicate (FeSiO₃), which is known as slag. This slag is less dense and can be easily removed from the furnace.
\[ \text{FeO} + \text{SiO}_2 \rightarrow \text{FeSiO}_3 \text{ (slag)} \]

5. **Final Product:**
The remaining copper is then in the form of copper matte (Cu₂S + FeS), which can be further processed to obtain pure copper.

6. **Conclusion:**
The addition of silica during the extraction of copper from its sulfide ore primarily serves to remove impurities, specifically iron oxide, by forming slag.

**Final Answer:**
The correct answer is: To remove impurities of iron oxide.

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