Past exam of the chemistry course of the year 1 of the natural sciences course of the University of Cambridge / 2025 / 5 / f / Solution

Adding the initiation step to the net forward trapping step cancels the nitrate-radical reaction intermediate:The net stoichiometry agrees with $-d[\mathrm{N}{\mathrm{O}}_2]/dt\simeq 2d[{\mathrm{N}}_2{\mathrm{O}}_5]/dt$ under the quasi-steady-state approximation.