represents a balance between opposing reactions. How sensitive is
this balance to changes in the conditions of a reaction? What outside
perturbations will change the equilibrium state? These are very
practical questions if, for example, one is trying to increase the
yield of a useful product in a reaction.
The easiest way to perturb a reaction and obtain more products is
to remove the products as fast as they are formed. This means that
the reaction is kept off-balance and that equilibrium is never achieved.
More and more reactants interact in a vain effort to maintain a
balance, as products are taken away. For example,
is quite soluble in water, whereas
only slightly soluble. Therefore washing the ammonia reaction mixture
with a spray of water dissolves and removes most of the ,
and leaves behind the unused
This sort of product removal does not change the actual conditions
of equilibrium; it only ensures that more
than would be the case if ,
to come to equilibrium without interference. The same trick of keeping
a reaction off-balance can be used if one of the products is a gas
that bubbles out of the reaction mixture, or a solid that precipitates.