What is the change in the oxidation state of nitrogen when $HNO_3$ is converted into $N_2O$?

Write the oxidation number of oxygen in $KO_{3}$ and $Na_{2}O_{2}$.

Match the following:

Compound	Oxidation number
$1$. $CrO_5$	$a$. $+6$
$2$. $H_2SO_4$	$b$. $+1$
$3$. $C_4OCl_2$	$c$. $-1$
$4$. $(CH_3)_2SO$	$d$. $+2$

In the following structure,the oxidation number of carbon is $H - N \rightrightarrows C$:

What is the oxidation number of carbon in methanal?

Calculate the oxidation number of sulfur,chromium,and nitrogen in $H_2SO_5$,$Cr_2O_7^{2-}$,and $NO_3^-$. Suggest the structures of these compounds and explain the fallacy in the direct calculation of the oxidation number for $H_2SO_5$.