Skip to content

Chemistry · Ch 6 — Chemical Kinetics

Average rate of chemical reaction

6.2.1

Average rate of chemical reaction

The average rate of a reaction is obtained by dividing the change in concentration of a reactant or product by the time interval over which the change occurs:

Average rate=change in concentration of a specieschange in time=ΔcΔt\text{Average rate} = \frac{\text{change in concentration of a species}}{\text{change in time}} = \frac{\Delta c}{\Delta t}

Consider the reaction A⟶B\mathrm{A \longrightarrow B}, in which A is consumed and B is produced. Because [A] decreases with time, the change Δ[A]\Delta[\mathrm{A}] is negative, and a minus sign is attached to make the rate itself a positive quantity:

average rate of consumption of A=−Δ[A]Δt\text{average rate of consumption of A} = -\frac{\Delta[\mathrm{A}]}{\Delta t}

average rate of formation of B=+Δ[B]Δt\text{average rate of formation of B} = +\frac{\Delta[\mathrm{B}]}{\Delta t}

Therefore, average rate of reaction=−Δ[A]Δt=+Δ[B]Δt\text{Therefore, average rate of reaction} = -\frac{\Delta[\mathrm{A}]}{\Delta t} = +\frac{\Delta[\mathrm{B}]}{\Delta t} …

Start your 14-day free trial to unlock the full solution →
← Previous · 6.2Rate of reactionsNext · 6.2.2 →Instantaneous rate of reaction