Average Rate
The overall change in concentration divided by the total time interval over which it occurred.
Formula / equation
rate_avg = Δ[A] / Δt
Unit
mol/(L·s)
In depth
Average rate is easy to measure but conceals how the rate varies during the interval. Because most reactions decelerate as reactants are used up, the average over a long period is much smaller than the initial rate and is of limited use in determining a rate law.
Examples in the real world
A reaction consuming 0.20 mol/L over 100 s has an average rate of 2.0 × 10⁻³ mol/(L·s).