Question

In a first order reaction, the initial conc. of the reactant was $M/10.$ After 8 minutes 20 seconds the conc. becomes $M/100.$
What is the rate constant?

• A. $5\times {10}^{-3}secon{d}^{-1}$
• B. $2.303\times {10}^{-5}secon{d}^{-1}$
• C. $2.303\times {10}^{-4}secon{d}^{-1}$
• D. $4.606\times {10}^{-3}secon{d}^{-1}$

Answer 1

The correct option is D $4.606\times {10}^{-3}secon{d}^{-1}$

As we know,

$K=\frac{2.303}{t}log\left[\frac{a_0}{a}\right]$

$K=\frac{2.303}{500}\log \left(\frac{\frac{1}{10}}{\frac{1}{100}}\right)$

$=\frac{2.303}{500}log\left(10\right)=4.606\times {10}^{-3}se{c}^{-1}$