Question

Calculate the oxidation number of $Mn$ in the product formed on strongly heating $M{n}_2{O}_7$.

(write absolute value of an answer)

Answer 1

When $2M{n}_2{O}_7$ is strongly heated, $Mn{O}_2$ is formed. The reaction is given below:
$2M{n}_2{O}_7\stackrel{\Delta }{\to }4Mn{O}_2+3O_2$.
Let $x$ be the oxidation number of $Mn$ in $Mn{O}_2$.
Hence, $x+2(-2)=0$ (equated to zero for a neutral compound)
or, $x=4$.
Hence, the oxidation number of $Mn$ in $Mn{O}_2$ is $+4$.