Question

A first-order reaction is $20$% complete in $10minutes$. Calculate the rate constant of the reaction (II) time taken for the reaction to go to $75$% completion.

Answer 1

It's a 1st Order Reaction

$k=\frac{2.303}{t}log\frac{100}{100-x}$

Here $x=20$%

$k=\frac{2.303}{10}log\frac{100}{100-20}$

$k=2.2\times {10}^{-2}{min}^{-1}$

In the 2nd Question,

$2.2\times {10}^{-2}=\frac{2.303}{t}log\frac{100}{25}$

$t=63min$