Chemistry - An unusual situation
An unusual situation
An unusual situation arises where the same number of particles occurs on
both sides of the equation describing an equilibrium system.
This system will respond as expected (along Le Chatelier lines) to the
addition or removal of a species or a change in temperature. However, a
change in pressure or volume has no effect on the position of equilibrium.
Consider the effect of an increase in pressure! By now the expected
response is that the position of equilibrium will move in the direction
that will reduce the total number of particles in the system, i.e. reduce
the pressure. Notice, however, that since there are the same number of
particles on both sides of the equation, there will be no change in the
total number of particles whether the system tries to shift to the left or
tries to shift to the right.
The overall effect is that gaseous equilibria in which there are the same
total numbers of particles on both sides of the equation are not disturbed
by a change in pressure or volume.
Another example of an imposed change that does not affect the
concentration fraction and hence does not alter the position of equilibrium
is the addition of an inert or non-reacting gas to an equilibrium system at
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