$A _{0} / A _{ t }$ at time $2\,min =?$
$K =\frac{2.303}{ t } \log \left[\frac{ A _{0}}{ A _{ t }}\right]$
$\frac{0 \cdot 693}{ t _{\frac{1}{2}}}=\frac{2 \cdot 303}{2} \log \left(\frac{ A _{0}}{ A _{ t }}\right)$
Or $\frac{2.303 \times 0.3010}{0.3010}=\frac{2.303}{2} \log \frac{ A _{0}}{ A _{ t }}$
$\log \frac{ A _{0}}{ A _{ t }}=2$
$\frac{ A _{0}}{ A _{ t }}=10^{2}=100$
( $\mathrm{R}=8.314 \mathrm{~J} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}, \log 4=0.6021$ આપેલ છે.)