Chemistry - Chemical Kinetics Question with Solution | TestHub

For a zero order reaction, the concentration of reactant at time $t$ is given by the integrated rate law:

$[A{]}_t=[A{]}_0-kt$

Substituting $[A{]}_0=100{\text{ mol dm}}^{-3}$, $k=1{\text{ mol dm}}^{-3}{\text{ s}}^{-1}$, and $t=90\text{ s}$:

$[A{]}_t=100-(1\times 90)=10{\text{ mol dm}}^{-3}$

The percentage of unreacted reactant is:

$\frac{[A{]}_t}{[A{]}_0}\times 100=\frac{10}{100}\times 100=10\%$

Answer: $10\%$