Stress on Equilibrium

Definition

Stress on equilibrium refers to any change imposed on a chemical system at equilibrium that disrupts its balance, causing the system to respond in a way that re-establishes a new equilibrium. This concept is crucial as it explains how changes in concentration, temperature, or pressure can affect the direction of the reaction and ultimately the concentrations of reactants and products.

5 Must Know Facts For Your Next Test

1. When a stress such as an increase in concentration of reactants is applied, the system shifts in the direction that consumes some of those reactants, producing more products.
2. Changes in temperature can shift the position of equilibrium depending on whether the reaction is exothermic or endothermic; adding heat to an exothermic reaction will favor the reactants.
3. Increasing pressure on gaseous reactions will shift the equilibrium toward the side with fewer moles of gas to alleviate the stress.
4. Removing a product from a reaction at equilibrium will cause the system to produce more of that product until a new equilibrium is reached.
5. The adjustments made by a system under stress are not instantaneous; they occur gradually as the reaction approaches a new state of balance.

Review Questions

• How does adding reactants affect a chemical system at equilibrium?
  • Adding reactants to a chemical system at equilibrium increases their concentration, creating a stress on the system. According to Le Chatelier's Principle, the system will respond by shifting the equilibrium position to the right, favoring the formation of products to counteract this increase in reactants. This shift continues until a new equilibrium is established with altered concentrations of both reactants and products.
• Evaluate how changes in temperature can impact an exothermic reaction at equilibrium and provide an example.
  • In an exothermic reaction, heat is released as a product. If the temperature is increased, this creates stress on the system, and according to Le Chatelier's Principle, the equilibrium will shift to favor the endothermic direction, which absorbs heat. For example, consider the reaction $$A + B \rightleftharpoons C + heat$$; raising the temperature would shift the equilibrium left, producing more A and B while decreasing C.
• Synthesize an argument discussing how understanding stresses on equilibrium can be beneficial in industrial processes.
  • Understanding stresses on equilibrium allows chemists and engineers to optimize industrial reactions by manipulating conditions to maximize yield. For example, in ammonia synthesis (Haber process), increasing pressure favors product formation due to fewer moles of gas on the product side. Additionally, controlling temperature can enhance efficiency, as managing these stresses effectively can lead to reduced costs and increased production rates. Thus, this knowledge is critical for improving sustainability and profitability in chemical manufacturing.

Related terms

Dynamic Equilibrium: A state in which the rate of the forward reaction equals the rate of the reverse reaction, resulting in constant concentrations of reactants and products.

Le Chatelier's Principle: A principle stating that if an external change is applied to a system at equilibrium, the system will adjust itself to counteract that change and restore a new equilibrium.

Equilibrium Constant (K): A numerical value that expresses the ratio of the concentrations of products to reactants at equilibrium for a given reaction at a specific temperature.