Give the steps involved in the extraction of metals of low and medium reactivity from their respective sulphide ores. 

Explanation

For metals, low in the reactivity series like mercury (Hg), the following steps are involved 
(i) Roasting (heating the ore strongly in the presence of excess of air) Metal sulphide is converted into metal oxide. 
`Oreoverset("Roastiong")to"Metal oxide (by heating in air)"`
`underset("ore")underset("Cinnabar")(2HgS)+underset("(from air)")underset("Oxygen")(3O_(2))overset("Roasting")tounderset("Mercury(II)oxide")(2Hg(l))+2SO_(2)`
(ii) Reduction Metal oxide is then reduced to metal by heating.
`"Metal oxide"underset("reduction")overset("Heat")to"Metal"`
`underset("Mercury (II) oxide")(2HgO(s))underset("reduction")overset("Heat")tounderset("Metal")underset("Mercury")(2Hg(l))+O_(2)(g)`
(iii) Refining of metal. For metals, medium in reactivity series like zinc (Zn), the following steps are involved
(i) Roasting (for sulphide ores) The sulphide ore is converted into metal oxide by heating the sulphide are strongly in the presence of air.
`underset("Zinc sulphide")(2ZnS(s))+underset("From air")(3O_(2)(g))overset(Delta)tounderset("Zinc oxide")(2ZnO(s))+underset("Sulphur dioxide")(2SO_(2)(g))`
(ii) Reduction Metal oxides are reduced to metals by using a suitable reducing agent. This can be done by either of two.
(a) Reduction by heating with carbon (smelting)
`underset("Zinc oxide")(ZnO(s))+underset("Coke")(C(s))overset(Delta)tounderset("Zinc")(Zn(s))+underset("Carbon monoxide")(CO(g))`
(b) Reduction by heating with aluminium
`underset("Iron(III)oxide")(Fe_(2)O_(3)(s))+underset("Aluminium")(2Al(s))overset(Delta)tounderset("Iron(melt)")(2Fe(l))+underset("Aluminium oxide")(Al_(2)O_(3)(s))`