During reaction $r$: $2CH_3\cdot(g)$ $\longrightarrow$ $CH_3CH_3(g)$ in a given time, the methyl disappear with a rate of $-1.2\frac{mol}{s}$ in a container of $0.5\; dm^3$, What is the reaction rate?
$v_{CH_3\cdot}$ $=$ $-\frac{1.2}{0.5}\frac{mol}{L\cdot s}$ = $-2.4\frac{mol}{L\cdot s}$ $v_r=$ $-(-\frac{2.4}{2}\frac{mol}{L\cdot s})$ = $1.2\frac{mol}{L\cdot s}$
