Chemical kinetics ia a way of measuring what are called reaction rates, or the speed of a reaction. There are a variety of factors that can affect the rate of reaction. The rate of a reaction is independent of the reaction's spontaneity. That is, just because a reaction is spontaneous (a negative free energy value) does not imply that the reaction is fast. For example, rusting is a spontaneous process. However, rusting is not a fast process. The variables that determine a reaction's spontaneity are very different than the variables that determine the rate of a reaction.