Question

The compound(s) that is(are) removed as slag during the extraction of copper is 
(A) CaO 
(B) FeO 
(C) Al₂O₃ 
(D) ZnO 
(E) NiO 
Choose the correct answer from the options given below :

• A. (C), (D) only
• B. (A), (B), (E) only
• C. (A), (B) only
• D. (B) only

Answer 1

The Correct Option is D

During the extraction of copper from its ores, the main process involved is smelting, where the ore is extracted by heating it in the presence of a reducing agent, typically carbon or carbon monoxide. One of the by-products formed during this process is slag, which consists primarily of a mixture of metal oxides and silicates.

In the extraction of copper, iron is frequently found in the form of iron oxide (FeO). The following reactions typically occur:

1. Iron oxide reacts with the silica (SiO₂) present in the furnace to form a slag, which is removed from the crucible. The reaction is as follows: FeO + SiO_{2} \rightarrow FeSiO_{3}.
2. This slag, iron silicate (FeSiO₃), can be easily separated from the molten copper due to its lighter density in comparison to the copper.

Now, let's examine the options:

• (A) CaO: Calcium oxide is typically used as a flux and not formed as a slag in copper extraction.
• (B) FeO: Iron oxide reacts with silica to produce the slag (FeSiO₃), which is the compound actually removed during the copper extraction process. Thus, FeO is a key component of the slag.
• (C) Al₂O₃: This is unlikely to be part of the slag in typical copper smelting processes.
• (D) ZnO: Zinc oxide is not commonly found as a slag during copper extraction.
• (E) NiO: Nickel oxide is not typically involved in slag formation in the context of copper extraction as described above.

Therefore, the correct answer is (B) only because FeO (iron oxide) is indeed the compound frequently reacted to form slag during the copper extraction process.