The rate law for the reaction $2\mathrm{NO}\left(\mathrm{g}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right)\to {\mathrm{N}}_2\mathrm{O}\left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)$ is given $\mathrm{d}p\left({\mathrm{N}}_2\mathrm{O}\right)/\mathrm{d}t=k{\left(p_{\mathrm{NO}}\right)}^2\left(p_{{\mathrm{H}}_2}\right)$ If ${\left({\mathrm{p}}_{\mathrm{NO}}\right)}_0$ is very much larger than ${\left(p_{{\mathrm{H}}_2}\right)}_0,$ , then the reaction follows