Question

Calculate the oxidation number of Iodine $\left(I\right)$ in $K{I}_3$ ?

• A. $+4$
• B. $+4$
• C. $-\frac{1}{4}$
• D. $-\frac{1}{3}$

Answer 1

The correct option is D $-\frac{1}{3}$

Let the oxidation number of $I$ is $x$ in$K{I}_3$.

$\Rightarrow 1+3\times \left(x\right)=0$
$x=-\frac{1}{3}$.

Alternative way :
$K{I}_3,isKI+I_2$
$\therefore$ $I$ has two oxidation no. -1 and 0 respectively.

However factualy speaking oxidation number of $I$ in $K{I}_3$ is an average of three values -1, 0, 0.

$\Rightarrow \text{Average}O.N.=\frac{-1+2\times \left(0\right)}{3}=-\frac{1}{3}.$