Question

In the extraction of nickel by Mond process, the metal is obtained by:

• A. Electrochemical reduction
• B. Thermal decomposition
• C. Chemical reduction by aluminium
• D. Reduction by carbon

Answer 1

Answer: (B)

Thermal decomposition

Mond process is a technique to extract and purify nickel. This process converts nickel oxides into pure nickel. This process makes use of the fact that carbon monoxide complexes with nickel readily and reversibly to give nickel carbonyl. Process contains these steps:
First impure nickel is reacted with excess carbon monoxide at ${60}^{o}C-{80}^{o}C$ to form the gas nickel carbonyl, leaving the impurities as solids.

180°C

$Impurenickel+CO\stackrel{{60}^{o}C-{80}^{o}C}{\to }Ni(CO{)}_4\stackrel{{180}^{o}C}{\to }Ni+4CO$

Then, the mixture of excess carbon monoxide and nickel carbonyl is heated to ${180}^{o}C$. On heating, nickel tetracarbonyl decomposes to give nickel. So, the metal is obtained by thermal decomposition.