When a reversible reaction occurs in apparatus which prevents the escape of reactants and products, equilibrium is reached when the forward and reverse reactions occur at exactly the same rate.
The effect of changing conditions on equilibrium
The relative amounts of all the reactants and products at equilibrium depend on the conditions of the reaction.
If a system is at equilibrium and a change is made to any of the conditions, then the system responds to counteract the change.
The effects of changing conditions on a system at equilibrium can be predicted using Le Chatelier’s Principle.