The rate constant of a zero order reaction is $2.0 \times$ $10^{-2} \mathrm{~mol} \mathrm{~L}^{-1}…
The rate constant of a zero order reaction is $2.0 \times$ $10^{-2} \mathrm{~mol} \mathrm{~L}^{-1} \mathrm{~s}^{-1}$. If the concentration of the reactant after 25 seconds is $0.5 \mathrm{M}$. What is the initial concentration?
$0.5 \mathrm{M}$
$1.25 \mathrm{M}$
$12.5 \mathrm{M}$
$1.0 \mathrm{M}$
Solution
For a zero order reaction
$
\begin{aligned}
& \text { Rate constant }=\mathrm{k}=\frac{a-x}{t} \\
& 2 \times 10^{-2}=\frac{a-0.5}{25} \\
& a-0.5=0.5 \\
& a=1.0 \mathrm{M}
\end{aligned}
$