Question

Extraction of copper by smelting uses silica as an additive to remove:
A. \[C{u_2}O\]
B. \[FeS\]
C. \[FeO\]
D. \[C{u_2}S\]

Answer 1

Hint: Smelting is a metallurgical process of extracting copper from its ore Chalcopyrite. In this reaction silica is used to remove oxide impurities and form \[FeSi{O_3}\] as a product.

Complete step by step answer:
Copper extraction refers to the methods or process used to obtain copper from its ores. The extraction of copper consists of a series of physical and electrochemical processes. Various methods have been evolved with the country depending on the ore source, local environment regulations and other factors. Oxidised copper ores can be treated by hydrometallurgical extraction.

The most common ore used in the extraction of copper is Chalcopyrite ( \[CuFe{O_2}\] ) also known as Copper pyrites and other sulphides. The concentration of ore is required and it is done by Froth Floatation method.

Smelting is a metallurgical technique to extract base metals from their ores with the help of heat and a chemical reducing agent. Smelting is used for metals like silver, iron, copper and other base metals. In copper smelting, concentrate ore is strongly heated with silica or silicon dioxide, calcium carbonate ( \[CaC{O_3}\] ) and air in a furnace. The major steps in extraction of copper are as given below:
1. Copper in Chalcopyrite is reduced to copper sulphide
2. Calcium carbonate is added as a flux to create the slag
3. Iron in Chalcopyrite is removed as iron silicate slag
4. Most of the sulphur in Chalcopyrite turns into Sulphur dioxide

The reaction is as given below:
\[2CuFe{S_2} + 2Si{O_2} + 4{O_2} \to C{u_2}S + 2FeSi{O_3} + 3S{O_2}\]
In this reaction, \[FeSi{O_3}\] slag is formed from \[FeO\] which is called gangue and \[Si{O_2}\] which is flux. Here, \[FeO\] is the basic impurity in the ore. The slag formation reaction is as given below.
\[FeO + Si{O_2} \to FeSi{O_3}\]
Therefore, in this reaction we use silica to remove \[FeO\] or gangue.

Therefore, the correct answer is option C. \[FeO\]

The copper extracted from this process is mixed with the slag and is called Matte Copper due to its texture appearance.

Note:
The gauge here is \[FeO\] is called iron oxide or ferrous oxide and is the basic impurity in the copper ore. Smelting process removes this impurity using silica additives. \[\]