Question

A generic reaction of aA———> products, gives a straight line plot of ln[A] versus time with a slope of -7.71x10^-3 Ms^-1. Assuming that the initial concentration of A is 0.135M, calculate the time in second,t, required for 25.6% of the original sample to react.

Answer 1

The given generic reaction is a First Order reaction.

Slope = -k = $-7.71\times 10^{-3}$

Hence, k = $7.71\times 10^{-3}$

Initial concentration = a = 0.135M

We know in the first order reaction,

$t = \dfrac{2.303}{k}log\dfrac{a}{a-x}$

$t= \dfrac{2.303}{7.71\times 10^{-3}}log\dfrac{0.135}{0.135 - \dfrac{25.6}{100}\times 0.135}$

Hence, $t = 38.35$ s