This threshold energy, Ea is called the energy of activation. It can be thought of as a barrier that the reaction must surmount before it can go to completion (see fig 10 opposite). From the usual random distribution of energy
among molecules, the fraction of molecules that have enough kinetic energy
to collide with energy Ea
or greater is
This fraction increases with temperature. At
absolute zero, it has the value: As the temperature approaches infinity, the
fraction of molecules capable of reacting approaches unity, no matter
how large the activation energy, Ea,
might be: At any finite temperature, the larger the activation
energy, the smaller the fraction of molecules that have enough energy
to surmount this barrier and react. The simple collision theory of chemical
reaction states that the rate
constant can be represented by |