What should be the considerations during the extraction of metals by electrochemical method?

Explanation

During extraction of metals by electrochemical method, the following two points must be considered to that proper precautions can be taken :
(i) Reactivity of of metals. If the metals are quite reactive and are expected to react with water , i.e, Na, Ca, Al, etc. then the metals should be extracted by electrolysis of their purified molten ores rather than their aqueous solutions. For example, Al is extracted by electrolysis of molten alumina.
(ii) Suitability of electrodes. The electrodes selected should not react with the products of electrolysis. If at all they react, then the electrodes must be made up of a metarial which is quite cheap sincee their periodic replacement should not increase the cost of the process. For example, in the electrolysis of alumina, ` O _ 2 ` is liberated at the anode. If Fe or Al is made as the anode, it will be attacked by ` O _ 2 ` forming ` Fe_2 O _ 3 or Al _ 2 O _ 3`. As a result, the anode will be eaten away. Instead of Fe and Al, the anodes of carbon are preferred because carbon is much cheaper than Fe or Al. Thus, electrolysis of ` Al _ 2 O _ 3 ` is carried out in an electrolytic tank using carbon as anode.