Question

In a first order reaction, the concentration of the reactant decreases from 800 mol $d{m}^{-3}$ to 50 mol $d{m}^{-3}$ in $2\times {10}^{4}s.$ The rate constant of the reaction in $\left(s^{-1}\right)$ is
(IIT-JEE, 2003)

• A. $2\times {10}^4$
• B. $3.45\times {10}^{-5}$
• C. $1.386\times {10}^{-4}$
• D. $2\times {10}^{-4}$

Answer 1

The correct option is C $1.386\times {10}^{-4}$

$k=\frac{2.303}{t}log\frac{[A{]}_0}{[A{]}_1}=log\frac{800}{50}=1.386\times {10}^4{s}^{-1}$