Question

In the extraction of nickel by Mond process, the metal is obtained by:
A.Electrochemical reduction
B.Thermal decomposition
C.Chemical reduction by aluminum
D.Reduction by carbon

Answer 1

Mond process is a technique to extract and purify nickel. This process converts nickel oxides into pure nickel. The nickel oxide and impurities react with the hydrogen gas to form an impure solid nickel. Further, nickel reacts with carbon monoxide and forms nickel carbonyl.

Complete step by step answer:
Nickel is recovered through extractive metallurgy. It is extracted from its ores by conventional roasting and reduction processes that yield a metal of greater than $75\%$ purity.
Mond process is a technique to extract and purify nickel. Carbon monoxide complexes with nickel readily and reversibly to give nickel carbonyl. The steps are listed below:
Firstly, impure nickel is reacted with excess carbon monoxide at ${60^ \circ }C - {80^ \circ }C$to form nickel carbonyl gas. (Leaving the impurities as solids)
Impure nickel +$CO$ $\xrightarrow{{60 - {{80}^ \circ }c}}Ni{(CO)_4}\xrightarrow{{{{180}^ \circ }C}}Ni + 4CO$
After that the mixture of excess of carbon monoxide and nickel is heated to ${180^ \circ }C$.
On heating, Nickel tetracarbonyl decomposes to give nickel.
Therefore, the metal is obtained by thermal decomposition.

Hence, option B is correct.

Note:
Thermal decomposition is a chemical decomposition caused by heat. The reaction is generally endothermic as heat is required to break chemical bonds in the compound undergoing decomposition. A thermal decomposition may be a reversible or irreversible reaction. Decomposition of calcium carbonate to calcium oxide and carbon dioxide on heating is an important decomposition reaction used in various industries.