Question

The oxidation number of cobalt in $K[Co(CN{)}_4]$ is

• A. +1
• B. -1
• C. +3
• D. -3

Answer 1

Answer: (C)

Let O.S. of Co in the complex = $x$
O S. of K = + 1.O.S. of CN = -1
1 + $x$ + 4(-1) = 0
$x$ = 3