In the reaction$2\mathrm{NO}+{\mathrm{O}}_2\to 2{\mathrm{NO}}_2$, if the rate of disappearance of ${\mathrm{O}}_2$ is $16 \mathrm{gm} \min$, then the rate of appearance of ${\mathrm{NO}}_2$ is

$$\begin{gathered} \begin{array}{rl} & 2\mathrm{NO}+{\mathrm{O}}_2\to 2{\mathrm{NO}}_2\\ =& -\frac{1\mathrm{d}\left[\mathrm{NO}\right]}{\mathrm{dt}}=\frac{-\mathrm{d}\left[{\mathrm{O}}_2\right]}{\mathrm{dt}}=\frac{1}{2}\frac{\mathrm{d}\left[{\mathrm{NO}}_2\right]}{\mathrm{dt}}\\ =& \frac{-\mathrm{d}\left[{\mathrm{O}}_2\right]}{\mathrm{dt}}=16{\mathrm{gmin}}^{-1}=\frac{16}{16}{\mathrm{molmin}}^{-1}=1\mathrm{mol}/\min \\ =& \frac{\mathrm{d}\left[{\mathrm{NO}}_2\right]}{\mathrm{dt}}=2\times \frac{-\mathrm{d}\left[{\mathrm{O}}_2\right]}{\mathrm{dt}}=2\times 1=2\mathrm{mol}/\min \end{array} \\ \text{No. of moles}=\frac{\text{weight}}{\text{mol.wt}} \\ 2\times \mathrm{Mol}\text{. wt of }{\mathrm{NO}}_2=\text{ wt } \\ 2\times 46=\mathrm{wt}\Rightarrow \text{ Weight of }{\mathrm{NO}}_2=92\mathrm{g} \\ \text{ Rate of appearance of }{\mathrm{NO}}_2=92\mathrm{gm}.{\min }^{-1}\approx 90\mathrm{gm}.{\min }^{-1} \end{gathered}$$

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