What is the effect of adding more reactant on the equilibrium of a chemical reaction?

When more reactant is added to a chemical reaction at equilibrium, the system responds according to Le Chatelier's principle, which states that if an external change is applied to a system at equilibrium, the system will adjust to counteract that change and restore a new equilibrium.

Adding more reactant increases its concentration, which disturbs the balance of the reaction. To counteract this change, the equilibrium will shift toward the products, or to the right, in order to consume the excess reactant. This results in the production of more products until a new equilibrium is established.

This principle highlights the dynamic nature of chemical equilibria, where changes in concentration, temperature, or pressure can lead to shifts in the position of equilibrium to favor either the reactants or the products. Thus, in this case, the addition of more reactant effectively drives the reaction forward, increasing the concentration of products relative to reactants until the system reaches a new state of balance.