Q55 of 65 Page 24

Give the reaction involved during extraction of zinc from its ore by

(a) roasting of zinc ore


(b) calcination of zinc ore


(a) 2ZnS (s) + 3O2→ 2ZnO+ 2SO2 (g)
(b) ZnCO3 (s) → ZnO (s) + CO2 (g)

Zinc is commonly extracted from its ore called zinc blende also known as zinc sulphide (ZnS). Firstly, froth flotation process removes gangue from sulphide ores. During roasting, the concentrated ore is finely ground and made to react with a stream of air. This converts zinc blende to zinc oxide (ZnO) which is more reactive. During calcination, the carbonate ore is heated strongly in the absence of air to convert it into metal oxide.


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