Question

describe a method for refining Nickel.

Answer 1

Nickel is heated in a stream of carbon monoxide forming a volatile complex, nickel tetracarbonyl.
$Ni+4CO\stackrel{330-350K}{\to }Ni(CO{)}_4$
NIckel tetracarbony is strongly heated to decompose, Thus, Pure nickel metal is obtained,
$\underset{tetracarbonyl}{\underset{Nickel}{Ni(CO{)}_4}}\stackrel{450-140K}{\to }\underset{Puremetal}{Ni}+\underset{monoxide}{\underset{Carbon}{4CO}}$
This is called Mond's process of Nickel is refined.