Question

The rate of the first order reaction, $A⟶$ Products, is $7.5\times {10}^{-4}$ $mol$ $L^{-1}{s}^{-1}$, when the concentration of $A$ is $0.2$ $mol$ $L^{-1}$. The rate constant of the reaction is:

• A. $2.5\times {10}^{-5}{s}^{-1}$
• B. $8.0\times {10}^{-4}{s}^{-1}$
• C. $6.0\times {10}^{-4}{s}^{-1}$
• D. $3.75\times {10}^{-3}{s}^{-1}$

Answer 1

The correct option is D $3.75\times {10}^{-3}{s}^{-1}$

$\because r\left(t\right)=k\left[A\right]$
$\therefore k=\frac{r\left(t\right)}{\left[A\right]}$
$⟹k=\frac{7.4\times {10}^{-4}}{0.2}$
$⟹k=3.75\times {10}^{-3}{s}^{-1}$