Question

Why is partial roasting of sulfide ore done in the metallurgy of copper?
A. An Auto-reduction of CuO formed is carried out by remaining CuS in the reaction.
B.Cu is separated by partial reduction due to sedimentation.
C. Due to the difference in gravity CuO and CuS are separated.
D. Complete roasting cannot be done in one step hence partial roasting is done.

Answer 1

To answer this question the concepts in metallurgy should be known. In metallurgy, many processes are used to concentrate the ore of the materials. Roasting and calcination are the known process for the concentration of ore. mineral and ore are two natural materials. The main source of ore and mineral is the earth. Metals and their components are found in minerals. The ore is the mineral from which metals can be extracted conventionally and cheaply.

Complete step by step answer:
In the case of the ore, the percentage of metal is greater than other minerals. For example, the ore of aluminum is bauxite. From bauxite, aluminum can be extracted cheaply and profitably. But aluminum is also found in clay, but it is not possible to extract aluminum from clay cheaply and profitably. That is why bauxite is the ore of aluminum.
To extract metals from ore the steps are,
-Concentration of ore.
-Conversion of the concentrated ore into metallic oxide.
-Reduction of metallic oxides.
-Refining the impure metal.
-Roasting is a metallurgical process involving a gas-solid reaction in presence of air at high temperatures to purify the ore of the material.
-Calcination is another process of metallurgy to purify the metal at high temperatures in absence of air.
But during both processes, the ore is heated below the melting temperature of the metal.
In the case of roasting of sulfide ore done in metallurgy of copper. Due to partial roasting, the copper sulfide becomes copper oxide which further reacts with unreacted copper sulfide and gives auto reduction. The reaction is shown below.
$2C{u_2}S{\text{ }} + {\text{ }}3{O_2}\; \to {\text{ }}2C{u_2}O{\text{ }} + {\text{ }}S{O_2}$ , $2C{u_2}O{\text{ }} + {\text{ }}C{u_2}S\; \to {\text{ }}6Cu{\text{ }} + {\text{ }}S{O_2}$ .

So, the correct option is A.

Note:
There are so many processes to purify metals, among them some efficient processes are,
Electrolytic refining: By this process copper (Cu) metal gets purified.
Zone refining: By this process Zinc (Zn) metal gets purified.
Van Arkel method: By this process titanium(Ti) metal gets purified from iodine.
The Mond process: By this process nickel (Ni) metal gets purified.