# For $rx^n$ $A\rightarrow B$,what is the time taken for which $[A_t]=1M$.Given :$K=2sec^{-1},[A_o]=10M$.

$\begin{array}{1 1}(a)\;1sec&(b)\;2.303sec\\(c)\;4.606sec&(d)\;\large\frac{2.303}{2}\normalsize sec\end{array}$

$t=\large\frac{1}{K}$$ln \large\frac{[A_0]}{[A_t]} for first order rx^n t=\large\frac{1}{2}$$ln \large\frac{10}{1}$
$\;\;=\large\frac{2.303}{2}$sec
Hence (d) is the correct answer.