• question_answer If a first-order reaction is completed to the extent of 60% and 20% in time intervals, ${{t}_{1}}$ and ${{t}_{2}},$ what is the ratio ${{t}_{1}}:{{t}_{2}}$ A) 6.32                              B) 5.58          C) 4.11        D) 8.33

${{t}_{1}}=\frac{2.303}{K}\log \left( \frac{100}{40} \right)$                                (i) ${{t}_{2}}=\frac{2.303}{K}\log \left( \frac{100}{80} \right)$                               .....(ii) From (i) and (ii), $\frac{{{t}_{1}}}{{{t}_{2}}}=4.11$