One
possible mechanism would be the collision of two N0 molecules to form
the unstable but perfectly legitimate N202
molecule, followed either by its decomposition to N0 again or its
collision with 02 to form N02:
This mechanism is shown in fig 5 opposite.
If we assume that the buildup and breakdown of N202
are very fast reactions in comparison with the collision of N202
and 02, and that the first two reactions
are in equilibrium,
then we can describe the association and dissociation reactions involving
constants k1 and k2
in terms of an equilibrium
constant:
k1[NO]2
= k2[N2O2]
The slower collision of N202
with 02 is called the rate-determining
step, since the overall reaction rate depends on how fast
the slowest step occurs. If the reaction takes place by collision
of N202 and
02, then the rate of production of N02
will be proportional to the concentrations of these two molecules: