Question

Which one of the following is the main process for extraction nickel in the pure form?
(A) Vapor phase refining
(B) Zone refining
(C) Electrolysis
(D) Solvent extraction

Answer 1

Hint: The process of purifying an impure metal is known as refining. There are many methods of refining metals such as distillation, poling, electrolysis, zone refining, vapor phase refining, etc. After refining, the final product obtained is chemically identical to the original one, but it is purer.

Complete answer: The main process used for the extraction of nickel in its pure form uses vapor phase refining. It is the process of refining a metal by converting the metal into its volatile compound and then decomposing it to get a pure metal. To use this method, the metal should form a volatile compound and also the volatile compound should be easily decomposed. Elements like nickel, titanium and zirconium are refined with this method. To make a volatile complex of the element nickel, it is heated in a steam of carbon monoxide gas. The volatile state of nickel is nickel tetracarbonyl. It is further decomposed to give pure nickel metal.
$Ni + 4CO\xrightarrow{{330 - 350K}}Ni{(CO)_4}$
$Ni{(CO)_4}\xrightarrow{{450 - 470K}}Ni + 4CO$
Therefore, option A is the correct answer.

Note:
In vapor phase refining, by heating the impure metal with a chemical reagent at low temperature, a volatile compound is formed. The volatile compound is decomposed further by heating to give a pure metal, for example, Mond’s process which is used for the extraction of nickel and Van-Arkel method that is used for preparing pure titanium are based on the principle of vapor phase refining.