Question

Write the characteristics of first order reaction.

Answer 1

(i) When the concentration of the reactant is increased by 'n' times, the rate of reaction is also increased by n times. That is, if the concentration of the reactant is doubled, the rate is doubled.
(ii) The unit of rate constant of a first order reaction is $se{c}^{-1}$ or $tim{e}^{-1}$
$k_1=\frac{rate}{(a-x)}=\frac{mol.li{t}^{-1}se{c}^{-1}}{mol.li{t}^{-1}}=se{c}^{-1}$
(iii) The time required to complete a definite fraction of reaction is independent of the initial concentration, of the reactant if $t_{1/u}$ is the time of one ${}^{\prime }{u}^{\prime }$the fraction of reaction to take place then from equation.
$k_1=\frac{2.303}{t}log\frac{a}{a-x}$
$x=\frac{a}{u}$ and $t_{1/u}=\frac{2.303}{k_1}log\frac{a}{a-\frac{a}{u}}$
$t_{1/u}=\frac{2.303}{k_1}loh\frac{u}{(u-1)}$
since $k_1$-rate constant $t_{1/u}$ is independent of initial concentration 'a'.