Shift in equilibrium

Definition

A shift in equilibrium refers to a change in the balance between reactants and products in a chemical reaction at equilibrium, often due to external changes in conditions such as concentration, temperature, or pressure. This dynamic process allows a reaction to respond to disturbances and re-establish a new equilibrium state, illustrating the principle of Le Chatelier's principle.

5 Must Know Facts For Your Next Test

1. A shift in equilibrium can occur with changes in concentration; adding more reactant will favor the formation of products.
2. Temperature changes can cause shifts; for endothermic reactions, increasing temperature shifts equilibrium to the right, while for exothermic reactions it shifts to the left.
3. Changes in pressure affect gaseous equilibria; increasing pressure shifts equilibrium towards the side with fewer moles of gas.
4. Catalysts do not cause a shift in equilibrium; they only speed up the rate at which equilibrium is reached.
5. The concept of shifts in equilibrium helps explain many biological and industrial processes, such as enzyme activity and chemical manufacturing.

Review Questions

• How does Le Chatelier's Principle explain the behavior of a system at equilibrium when subjected to changes in concentration?
  • Le Chatelier's Principle states that if an equilibrium system is disturbed by a change in concentration, the system will adjust to minimize that disturbance. For instance, if more reactant is added, the equilibrium will shift toward producing more products to counterbalance this increase. This dynamic adjustment demonstrates how chemical systems strive to maintain balance while responding to external changes.
• Describe how temperature affects the position of equilibrium in an exothermic reaction compared to an endothermic reaction.
  • In an exothermic reaction, heat is released as products are formed. When temperature increases, according to Le Chatelier's Principle, the system will shift toward the left to absorb some of that heat, favoring reactants. Conversely, for endothermic reactions that absorb heat, increasing temperature shifts the equilibrium to the right, favoring product formation as the system seeks to utilize the added heat. Understanding these shifts is crucial for controlling reaction conditions.
• Evaluate how changes in pressure influence chemical equilibria involving gaseous reactions and provide an example.
  • Changes in pressure have significant effects on equilibria involving gases due to the relationship between pressure and volume. According to Le Chatelier's Principle, increasing pressure will shift the equilibrium toward the side with fewer moles of gas. For example, in the reaction $$N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)$$, increasing pressure favors the production of ammonia ($$NH_3$$), as it has fewer moles of gas on its side compared to the reactants. This understanding helps optimize conditions for industrial ammonia synthesis.

Related terms

Le Chatelier's Principle: A principle stating that if a system at equilibrium is disturbed by a change in concentration, temperature, or pressure, the system will adjust to counteract that disturbance and restore a new equilibrium.

Equilibrium Constant (K): A numerical value that expresses the ratio of concentrations of products to reactants at equilibrium for a given reaction, allowing predictions about the position of equilibrium.

Dynamic Equilibrium: A state of balance in which the rates of the forward and reverse reactions are equal, resulting in constant concentrations of reactants and products over time.