JEE Main · 2026 · 06 Apr 2026 · Shift 1 · Compounds Containing Nitrogen

Diazoaminobenzene, ${\mathrm{C}}_6{\mathrm{H}}_5-\mathrm{N}=\mathrm{N}-\mathrm{NH}-{\mathrm{C}}_6{\mathrm{H}}_5$, on warming with excess aniline and a trace of aniline hydrochloride rearranges: the terminal $-\mathrm{NH}-$ linkage breaks and the diazonium end couples at the para position of an aniline ring. The yellow product is $p$-aminoazobenzene, ${\mathrm{C}}_6{\mathrm{H}}_5-\mathrm{N}=\mathrm{N}-{\mathrm{C}}_6{\mathrm{H}}_4-\mathrm{N}{\mathrm{H}}_2$, of molecular formula ${\mathrm{C}}_{12}{\mathrm{H}}_{11}{\mathrm{N}}_3$.

Molar mass $=12(12)+11(1)+3(14)=144+11+42=197\mathrm{g}\mathrm{mo}{\mathrm{l}}^{-1}$.

Mass percentage of nitrogen $=\frac{3\times 14}{197}\times 100=\frac{42}{197}\times 100=21.3\%$.

The nitrogen content of the yellow product is $21\%$.