The position of an
equilibrium is affected by many things.
This means that the relative concentrations of reactant and
products can differ. Although the rate of the
forward reaction is the same as
the rate of the reverse reaction, you can
still start off with more ammonia.
However, equilibria are affected by
concentration.
Haber
Process an Example of Keq
If there is more ammonia,
the equilibrium will shift to
try and make things
equal again. This means the reverse
reaction will speed up a bit, until
the concentrations are where they want to be, and then it
will return to a constant
dynamic equilibrium - forward and reverse reactions being the same.