What chemical kinetics studies
Chemical kinetics explains how fast reactions occur and which molecular steps control their rates. For a reactant A, an average disappearance rate over a time interval is −Δ[A]/Δt; for a product P, an average formation rate is +Δ[P]/Δt. A negative sign before a reactant change makes the reported reaction rate positive. Instantaneous or initial rate is obtained from the slope of a concentration-time curve at a chosen point. Common units are mol L−1 s−1.
For aA + bB → pP, stoichiometrically normalized rate is −(1/a)d[A]/dt = −(1/b)d[B]/dt = (1/p)d[P]/dt. This allows changes of different species to describe one reaction rate.