Question

Which one of the following reactions does not occur during extraction of copper?

• A. $CaO + SiO _2 \rightarrow CaSiO _3$
• B. $2 Cu _2 S +3 O _2 \rightarrow 2 Cu _2 O +2 SO _2$
• C. $FeO + SiO _2 \rightarrow FeSiO _3$
• D. $2 FeS +3 O _2 \rightarrow 2 FeO +2 SO _2$

Answer 1

The Correct Option is A

To determine which reaction does not occur during the extraction of copper, we need to understand the typical processes and reactions involved in copper extraction.

During the extraction of copper from its ores, especially using the pyrometallurgical method, the following key processes occur:

1. Roasting: This involves heating the ore in the presence of oxygen. For copper ores like copper sulfides, this results in reactions such as:
   • \(2 \text{Cu}_2 \text{S} + 3 \text{O}_2 \rightarrow 2 \text{Cu}_2 \text{O} + 2 \text{SO}_2\)
2. Fluxing: This step involves adding substances that help in removing impurities. In many smelting processes, silica \(\text{(SiO}_2\text{)}\) is often used to remove iron oxide \(FeO)\) by forming a slag:
   • \(\text{FeO} + \text{SiO}_2 \rightarrow \text{FeSiO}_3\)
3. Converting: Here, additional reactions occur to purify the metal further. Iron present is oxidized and removed:
   • \(2 \text{FeS} + 3 \text{O}_2 \rightarrow 2 \text{FeO} + 2 \text{SO}_2\)

Now let's evaluate each of the provided reactions:

• \(\text{CaO} + \text{SiO}_2 \rightarrow \text{CaSiO}_3\): This reaction involves lime (CaO) and silica (SiO₂) forming slag (CaSiO₃). However, this specific reaction is more typical in processes like steelmaking, not copper extraction, as lime is not typically a flux used in copper smelting.
• \(2 \text{Cu}_2 \text{S} + 3 \text{O}_2 \rightarrow 2 \text{Cu}_2 \text{O} + 2 \text{SO}_2\): This is a typical roasting reaction occurring during copper extraction.
• \(\text{FeO} + \text{SiO}_2 \rightarrow \text{FeSiO}_3\): This is a common slag formation reaction in copper smelting to remove iron impurities.
• \(2 \text{FeS} + 3 \text{O}_2 \rightarrow 2 \text{FeO} + 2 \text{SO}_2\): This reaction involves oxidation of iron sulfides, typical in many extraction processes including copper.

Hence, the reaction that does not typically occur during the extraction of copper is:
\(\text{CaO} + \text{SiO}_2 \rightarrow \text{CaSiO}_3\). This reaction is not a part of the copper extraction process as it uses lime instead of silica.