Question

The difference in oxidation state of chlorine$\left(Cl\right)$ in $HCl{O}_4$​ and $HCl{O}_3$​ respectively is:
(give magnitude only)

Answer 1

Let the oxidation state of chlorine be $x$ an $y$ in $HCl{O}_4$​ and $HCl{O}_3$​.
The oxidation number of $H$ and $O$ atoms in both $HCl{O}_4$​ and $HCl{O}_3$​ are $+1$ and $-2$ respectively.

$HCl{O}_4:$​
Let the oxidation number of $Clisx$
$+1+x\times (-8)=0x=8-1x=+7$

$HCl{O}_3:$
Let the oxidation number of $Clisy$
$+1+y\times (-6)=0y=6-1y=+5.$
Difference : $x-y=7-5=2$