Final answer:
Adding more reactants to a system in equilibrium will cause the system to shift, consuming the excess reactants to produce more products until a new equilibrium is established.
Step-by-step explanation:
When more reactants are added to a chemical reaction that had reached equilibrium, the system will respond to relieve the stress caused by the change in concentration. This response is in line with Le Chatelier's Principle, which predicts how a system at equilibrium will shift when it is subjected to a change.
If additional reactant is introduced, the reaction will consume some of this reactant to form more products, shifting the equilibrium to the right. Conversely, if a product is added, the system will shift to the left, consuming some of the product to form more reactants.
This process continues until a new equilibrium is established, with different concentrations of reactants and products compared to the original state.