This temperature dependence of collision
frequency is almost negligible in comparison with the exponential
temperature dependence of the e-Ea/RT
term, which gives the fraction of the colliding molecules with energy
greater than Ea.
The collision theory tells us how the experimental
constant should vary with temperature: There should be a straight-line
relationship between the logarithm of k and the reciprocal
temperature, 1/T, with a negative slope proportional to the
activation energy, Ea
If we measure k at several temperatures
and plot ln k against 1/T, we obtain an Arrhenius
plot (fig 11 opposite). (This kind of plot is named
after the Swedish chemist who first developed the theory. )
This is the most direct means of obtaining
the activation energy of a reaction, and is convincing evidence
for the entire picture of activation-energy barriers.
In order that the reverse reaction occurs,
the same energy level for the reaction intermediates must be achieved
by the collision of product
molecules. If product molecules are more stable than reactants
negative), then the energy of activation will be greater for the
reverse reaction than the forward.