Question

For a given reaction $t_{1/2}=\frac{1}{Ka}$The order of reaction

• A. $1$
• B. $0$
• C. $3$
• D. $2$

Answer 1

Answer: (D)

$t_{1/2}=\frac{1}{Ka}$ for second order reactions
$t_{1/2}=\frac{1}{K\left(a\right)}\Rightarrow t_{1/2}\propto \frac{1}{{\left[a\right]}^1}$
$\Rightarrow t_{1/2}\propto {\left[a\right]}^{-1}$
Also $t_{1/2}\propto {\left[a\right]}^{1-n}$
${\left[a\right]}^{n-1}={\left[a\right]}^{-1}\Rightarrow 1-n=-1=n=2$