Explain the relationship between forward and reverse
reactions at equilibrium and predict how changing the
amount of a reactant or product (creating a stress) will
affect that relationship.
For example (select one from each underlined section)
If the amount of (reactant or product) increases, the rate of the (forward or
reverse) reaction will increase or decrease) to reach a new equilibrium.
If the amount of (reactant or product) decreases, the rate of the (forward or
reverse) reaction will increase or decrease) to reach a new equilibrium.

If a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium shifts to counteract the change to reestablish equilibrium. If a chemical reaction is at equilibrium and experiences a change in pressure, temperature, or concentration of products or reactants, the equilibrium shifts in the opposite direction to offset the change. This page covers changes to the position of equilibrium due to such changes and discusses briefly why catalysts have no effect on the equilibrium position.

For example, if the system is changed in a way that increases the concentration of one of the reacting species, it must favor the reaction in which that species is consumed. In other words, if there is an increase in products, the reaction quotient, Qc, is increased, making it greater than the equilibrium constant, Kc.