Chapter 12

Chemical Kinetics

Thermodynamics and the study of chemical equilibrium tell us whether the occurrence of a reaction
is favorable and to what extent the reaction goes toward completion. However, a lot of reactions
that, from a free energy perspective, are expected to favor products heavily are not seen to proceed
readily in our everyday experience. For example, graphite is the more thermodynamically stable
state of carbon under standard conditions compared to diamond, but we probably have better
things to worry about than our diamonds turning into pencils. Similarly, combustion reactions of
hydrocarbons (a constituent of the human body) are exothermic and also tend to be entropically
favored, but we probably shouldn’t count on our enemies spontaneously erupting into flames. The
reason behind these observations is that thermodynamics reveals only part of the story about
chemical reactions. The inherent tendency of a reaction to occur does not necessarily have anything
to do with how readily or quickly it does take place. Furthermore, thermodynamics does not give us
a microscopic picture of how exactly a reaction is proceeding: How do the individual molecules
interact with one another to lead to the end product? How many steps does the reaction have to go
through? All these issues are investigated within the realm of chemical kinetics—the study of the
rates of reactions, the effect of reaction conditions on these rates, and the mechanisms implied by
such observations.

Reaction    Rates

Changes in  Concentration   Over    Time

Collision   Theory, Transition  States, and Energy  Profiles

Reaction    Mechanisms

Factors Affecting   Reaction    Rate

Dynamic Equilibrium