Question

What is the oxidation number of $Fe$ in $K_4\left[Fe\right(CN{)}_6]$?

Answer 1

Let the oxidation number of $Fe$ be $x$.
We know that, Ox. no. of $K$$=+1$
Ox. no. of $(CN{)}^{-}=-1$
So, $4(Ox.no.K)+Ox.no.Fe+6(Ox.no.C{N}^{-})=0$
$4(+1)+x+6(-1)=0$
or $+4+x-6=0$
or $x=+6-4=+2$
The oxidation number of iron in $K_{4}Fe(CN{)}_6$ is $+2$.