For reaction $a A \rightarrow x P$, when $[A]=2.2 \mathrm{mM}$, the rate was found to be $2.4 \mathrm{mM}…
For reaction $a A \rightarrow x P$, when $[A]=2.2 \mathrm{mM}$, the rate was found to be $2.4 \mathrm{mM} \mathrm{s}^{-1}$. On reducing concentration of $A$ to half, the rate changes to $0.6 \mathrm{mM} \mathrm{s}^{-1}$. The order of reaction with respect to $A$ is
1.5
2.0
2.5
3.0
Solution
$a A \rightarrow x P$
Rate of reaction $=[A]^a$
Order of reaction $=a$
$[A]_1=2.2 \mathrm{mM}, r_1=2.4 \mathrm{mM} \mathrm{s}^{-1}$
$[A]_2=\frac{2.2}{2} \mathrm{mM}, r_2=0.6$ or $\frac{2.4}{4} \mathrm{mM} \mathrm{s}^{-1}$
On reducing the concentration of $A$ to half, the rate of reaction is decreased by four times.
$\therefore$ Rate of reaction $\propto[A]^2$
$\Rightarrow$ Order of reaction $=2$