Question

Use of electrolysis is not done in ______.
A.Production of ${\text{Na}}$
B.Production of water
C.Purification of metal
D.Production of ${\text{KOH}}$

Answer 1

To solve this question you must recall the processes of production of various elements. Electrolysis is generally used in case of producing highly reactive metals, mostly of s-block.

Complete step by step answer:
The production of sodium metal is achieved through the Castner process. In this process, sodium is obtained by the electrolysis of sodium hydroxide at temperature higher than ${300^{\text{o}}}$ Celsius under which sodium hydroxide would solidify. Above this temperature, molten sodium produced at the cathode starts to dissolve in the melt.
The production of water does not involve electrolysis. Water is produced at the large scale by the reaction of hydrogen gas and oxygen gas under controlled circumstances.
The production of potassium hydroxide involves electrolysis of potassium carbonate in aqueous medium. Potassium hydroxide is obtained in the electrolytic mixture and hydrogen gas is released at the cathode. Carbon dioxide gas and oxygen gas are evolved at the anode.
Electrolysis is commonly used for the purification and extraction of metals from their ores. This process is known as electrolytic refining.

Thus, the correct option is B.

Note:
Electrolytic refining is a very common method for the purification of metals. In this process, a block of impure metal is taken as the anode and a thin sheet of pure metal becomes the cathode. Both the electrodes are dipped in an electrolytic cell which contains the aqueous solution of a metal salt. When electric current of a specific voltage is passed through the circuit, the impure metal dissolves in the solution and then pure metal deposits at the cathode. The impurities settle down below the anode and pure metal is obtained at the cathode.