(i) The end product of both the processes is oxide of metal.
(ii) Volatile impurities are removed from the ore and surface area for the further reaction increases.

Sulphide ores are generally roasted in reverberatory furnace in free supply of air below its melting point. Ore changes to oxide with larger surface area and volatile impurities are removed.
\(2ZnS+{ 3O }_{ 2 }\overset { \Delta }{ \longrightarrow } 2ZnO+{ 2SO }_{ 2 }\)
\(2PbS+{ 3O }_{ 2 }\overset { \Delta }{ \longrightarrow } pbO+{ 2SO }_{ 2 }\)

(i) Sulphide ores thermodynamically are more stable than CS₂ and hence cannot be converted by using coke as reducing agent.
(ii) Moreover CO₂ is more volatile and thermodynamically more stable than CS₂.
(iii) Thus \(\Delta G^{ 0 }\) of a metal sulphide is not compensated by the energy of reaction of metal sulphide, with coke. 
(iv) Hence, it is better to convert the sulphide ore to oxide form and then subject to smelting (i.e) carbon reduction method.

SiO₂ is used in the metallurgy of copper to remove FeO as FeSiO₃ (slag) (i.e) acidic flux is used to remove basic impurities.
\(FeO+{ SiO }_{ 2 }\longrightarrow { FeSiO }_{ 3 }\)

Distillation, liquation, electrolytic refining, zone refining, vapour phase method, van -Arkel method

Iron, Lead and Copper

Metal oxides to metal : Carbon, carbon monoxide, hydrogen, aluminum and metals like sodium.

(i) Conversion of ores into oxides.
(ii) Reduction of metal oxides.

Gravity separation, froth flotation, leaching, magnetic separation

The choice of method will depend on the nature of the ore, type of impurity and environmental factors

The preliminary step in metallurgical process is removal of the impurities. This removal process is known as concentration of ore.

Copper, Silver, Gold and Platinum

It is essential to design an eco friendly metallurgical process that would minimize waste, maximize energy efficiency. Such advances in metallurgy is vital for the economic and technical progress in the current era.

Metallurgy relates to the science and technology of metals. The various steps involved in the extraction of metals form their ores as well as refining of crude metals are collectively know as metallurgy.

Ellingham diagram for the formation of ZnO and CO₂ intersects around 1200 K. Above this temperature ZnO lies above Carbon which indicates Carbon is the better reducing agent CO is more effective reducing agent only below 983 K.