Time Dependence of Chemical Reaction Rates

The rate of chemical reaction (r) is the most fundamental concept in chemical kinetics. Yet the dependence of r on time i.e. the change of reaction rate as the reaction proceeds is not explicitly discussed in chemical education literature. We derived appropriate equations and discuss explicitly how r changes with time. The derivation of r(t) expressions is given for reactions with simple kinetic forms r=kcn and for some reactions with more complex kinetic forms (e.g. autocatalytic or consecutive reactions). Our approach demonstrates clearly that while the reaction rate and concentration are both functions of time they are represented by different mathematical functions and sometimes show distinctly different temporal behavior.