Chemistry - Redox Reactions Question with Solution | TestHub

In $\mathrm{N}{\mathrm{H}}_4\mathrm{N}{\mathrm{O}}_2$, nitrogen is present as -3 ($\mathrm{N}{\mathrm{H}}_4^{+}$) and +3 ($\mathrm{N}{\mathrm{O}}_2^{-}$); both go to 0 in ${\mathrm{N}}_2$, a change of oxidation state (redox). In (a), (c) and (d) no element changes oxidation state. Hence (b).