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

The remaining fraction is $\boxed{0.120\approx 12.0\%}$. Using the tabulated $300\mathrm{K}$ value rather than replacing it by the fitted value, the constant ozone concentration makes nitrogen dioxide loss a pseudo-first-order reaction:Integrating with initial concentration $[\mathrm{N}{\mathrm{O}}_2{]}_0$ and $t=8(3600)=28800\mathrm{s}$ givesThis uses the nitrate-radical quasi-steady-state approximation over the interval, constant temperature and ozone concentration, and no extra nitrogen dioxide sources or sinks. The stated $\mathrm{c}{\mathrm{m}}^3$ and $\mathrm{mol}\mathrm{c}{\mathrm{m}}^{-3}$ units cancel directly; no factor of $1000$ is needed.