Question

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

• A. electrochemical reduction
• B. thermal decomposition
• C. chemical reduction by aluminium
• D. reduction by carbon

Answer 1

The correct option is B thermal decomposition

In Mond's process, nickel oxide is reacted with water gas, a mixture of $H_2$ and $CO$, at atmospheric pressure and a temperature of ${50}^{o}C$. The oxide is thus reduced to impure nickel. Reaction of this impure material with residual carbon monoxide gives the toxic and volatile compound, nickel tetracarbonyl, $Ni(CO{)}_4$. This compound decomposes on heating to about ${230}^{o}C$ to give pure nickel metal and $CO$, which can then be recycled.
Therefore thermal decomposition is the correct answer.