Chapter 13 we were concerned with the question: Will a given reaction
ever take place spontaneously, even if one waits forever? The answer
was that any reaction that leads to a lower free energy will
occur spontaneously. Any reaction that requires an increase
in free energy will not; it will be spontaneous in the reverse direction
instead. Now we come to a more difficult but very practical question
in this and the following chapter: Granted that a given reaction
is spontaneous, how far will it go, and will it take place within
a reasonable time? What factors determine the rates of chemical
chemical reactions appear to go essentially to completion, ending
with products and an undetectable or negligable amount of reactants.
Some but not all of these reactions also are very fast (e.g., explosions).
Other reactions stop short of completion and remain a mixture of
reactants and products after all visible chemical change is over.
Still other reactions do not appear to take place at all within
a reasonable time, even though their calculated free energy change
is quite negative.