Question

(a) Name two metals which are found in free state in nature.
(b) What chemical process is used for extracting a metal from its oxide ore? Name one metal which is extracted by this method.
​(c) Describe the extraction of zinc metal from its sulphide ore as well as its carbonate ore. Write equations of all the reactions involved.

Answer 1

(a) Metals in the bottom of the reactivity series are found in the free state. For eg. gold, platinum, silver, etc.

(b) Metal can be extracted from its oxide ore by electrolytic reduction. Aluminium metal can be extracted by electrolytic reduction of molten aluminium oxide.

$2{\mathrm{Al}}_2{\mathrm{O}}_3\left(\mathrm{l}\right)\to 4\mathrm{Al}\left(\mathrm{l}\right)+3{\mathrm{O}}_2\left(\mathrm{g}\right)$

(c) Zinc is extracted from its carbonate ore by calcination process in which carbonate ore is heated strongly in the absence of air to convert it into zinc oxide.

$\underset{\mathrm{zinc}\mathrm{carbonate}\mathrm{ore}}{{\mathrm{ZnCO}}_3\left(\mathrm{s}\right)}\stackrel{\mathrm{calcination}}{\to }\mathrm{ZnO}\left(\mathrm{s}\right)+{\mathrm{CO}}_2\left(\mathrm{g}\right)$

Zinc sulphide is extracted from its sulphide ore by roasting process in which sulphide ore is heated strongly in the presence of air to convert it into zinc oxide.

$\underset{\mathrm{zinc}\mathrm{sulphide}}{2\mathrm{ZnS}\left(\mathrm{s}\right)}+3{\mathrm{O}}_2\left(\mathrm{g}\right)\stackrel{\mathrm{roasting}}{\to }2\mathrm{ZnO}\left(\mathrm{s}\right)+2{\mathrm{SO}}_2\left(\mathrm{g}\right)$