Question

What are the units of the rate of reaction?

Answer 1

Rate of reaction:

• “The rate of a reaction can be defined as the change in concentration of a reactant or product in unit time”.
• Consider a reaction, $\mathrm{R}\to \mathrm{P}$. Thus, the rate of reaction can be represented as:

$$\begin{gathered} \mathrm{Rate}\mathrm{of}\mathrm{disappearance}\mathrm{of}\mathrm{R}=\frac{\mathrm{Decrease}\mathrm{in}\mathrm{concentration}\mathrm{of}\mathrm{R}}{\mathrm{Time}\mathrm{taken}}=\frac{\left[\mathrm{R}\right]}{\mathrm{t}} \\ \mathrm{Rate}\mathrm{of}\mathrm{appearance}\mathrm{of}\mathrm{P}=\frac{\mathrm{Increase}\mathrm{in}\mathrm{concentration}\mathrm{of}\mathrm{P}}{\mathrm{Time}\mathrm{taken}}=\frac{\left[\mathrm{P}\right]}{\mathrm{t}} \end{gathered}$$

Units of reaction:

• As the concentration is in $\mathrm{mol}{\mathrm{L}}^{-1}$ and time is in $\mathrm{s}$ ,then the units will be $\mathrm{mol}{\mathrm{L}}^{-1}{\mathrm{s}}^{-1}$.
• Thus, the unit of the reaction is $\mathrm{mol}{\mathrm{L}}^{-1}{\mathrm{s}}^{-1}$.