Question

In a first order reaction the concentration of reactant decreases from 800 $mol/d{m}^3$ to $50mol/d{m}^3$ in $2\times {10}^{4}sec$. The rate constant of reaction in $se{c}^{-1}$ is:

• A. $2\times {10}^4$
• B. $3.415\times {10}^{-5}$
• C. $1.386\times {10}^{-4}$
• D. None of these

Answer 1

Answer: (C)

$1.386\times {10}^{-4}$

As we know,

$t=\frac{2.303}{k}log\left(\frac{N_0}{N}\right)$
$k=\frac{2.303}{2\times {10}^4}log\left(\frac{800}{50}\right)=1.386\times {10}^{-4}se{c}^{-1}$