Final answer:
When additional reactant is added to a system at equilibrium, the equilibrium will shift to the right. If a product is added, the equilibrium will shift to the left.
Step-by-step explanation:
When additional reactant is added to a system at equilibrium, the equilibrium will shift to the right, favoring the formation of products. This is because the system needs to reduce the stress caused by the increase in reactant concentration. On the other hand, if a product is added, the equilibrium will shift to the left, favoring the formation of reactants. This is done to reduce the stress caused by the increase in product concentration.
66