Question

In balancing the half-reaction :
$CN ^{-} \longrightarrow CNO ^{-}$(skeletal) the number of electrons that must be added is :

• A. $0$
• B. $1$ on the right
• C. $1$ on the left
• D. $2$ on the right

Answer 1

Answer: (D)

$CN^{-} \rightarrow CNO^{-}$
Oxidation number of nitrogen in $CN^{-}4+x=-1$ and in $CNO^{-}4+x-2=-1$
$x=-5,x=-3$
$CN^{-}$ is thus oxidised by losing two electrons.