In a chemical equilibrium, what can happen if the system is subjected to a change?

In a chemical equilibrium, when a system is subjected to a change, such as alterations in concentration, temperature, or pressure, the system responds by shifting the equilibrium position to counteract that change. This behavior is articulated by Le Chatelier's principle, which states that if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium moves to counteract the change and re-establish balance.

For example, if the concentration of a reactant is increased, the system will shift towards producing more products to reduce the effect of the added reactant. Similarly, if the temperature is raised in an exothermic reaction, the equilibrium will shift toward the reactants to absorb some of the excess heat. This self-adjustment reflects the system's tendency to maintain stability despite external changes.

In contrast, the other options describe scenarios that do not align with the principles governing chemical equilibrium. For instance, the equilibrium cannot remain completely unchanged in response to external factors, nor does it completely halt the reaction. Additionally, while concentration changes may lead to a decrease in the concentration of products, this is a result of the system adjusting rather than a direct consequence of the change itself. Thus, the correct understanding of how equilibrium systems operate under perturbations is captured by the