Which is the role of HNO₃ in the nitrating mixture used for nitration of benzene?

In Amines, the nitrogen atom bonds with alkyl or aryl groups replacing hydrogen, whereas in amides, the nitrogen atom bonds directly with the carbonyl group (-CO-).

Kjeldahl's method is not applicable to compounds containing nitrogen in nitro and azo groups and nitrogen present in the ring.

$C{H}_{3}C{H}_{2}N{O}_2\stackrel{573K}{\to }C{H}_2=C{H}_2+HN{O}_2$

Correct order of basic strength in aqueous medium is

${\left(C{H}_3\right)}_{2}NH>C{H}_{3}N{H}_2>{\left(C{H}_3\right)}_{3}N>N{H}_3$

Kindly consider the following figure