If additional reagent A is added to the system at equilibrium, the instantaneous concentration of A is too large; Q is too small and A and B are consumed to produce more C.
If additional product C is added to the system at equilibrium, the instantaneous concentration of C is too large; Q is too large and C reverts back to form A and B.
Le Chatelier's Principle requires that the system undergo reaction in a manner to change the concentrations and pressure so that the disturbance is removed. |