Initial conc. $A_{0}=0.1\, M$
Conc. After $5 \min A_{t}=0.001\, M$ $t =5\, min$.
For first order reaction
$K =\frac{2.303}{t} \log \left(\frac{A_{0}}{A_{t}}\right)$
$=\frac{2.303}{5} \log \left(\frac{0.1}{0.001}\right)$
$K =0.9212 \,\min ^{-1}$
(આપેલ છે: $\left. R =8.314\, J\, mol ^{-1} K ^{-1}\right)$