key term - Equilibrium

Definition

Equilibrium refers to the state in a chemical reaction where the rates of the forward and reverse reactions are equal, resulting in constant concentrations of reactants and products over time. This dynamic balance means that even though reactions are occurring, there is no net change in the concentrations of the substances involved. Understanding equilibrium is essential for grasping concepts such as Gibbs free energy and spontaneity of reactions, as it helps determine whether a reaction can occur under specific conditions.

5 Must Know Facts For Your Next Test

1. At equilibrium, the concentrations of reactants and products remain constant but not necessarily equal; it depends on the specific reaction.
2. Equilibrium can be affected by changes in temperature, pressure, and concentration, which can shift the position of the reaction to favor either reactants or products.
3. The equilibrium constant (K) quantifies the ratio of product concentrations to reactant concentrations at equilibrium, providing insight into how far a reaction goes towards completion.
4. In spontaneous reactions, Gibbs free energy decreases as the system moves towards equilibrium, indicating that products are favored over reactants.
5. Reactions can reach different equilibria depending on initial conditions; thus, knowing how to manipulate these conditions is crucial for controlling chemical processes.

Review Questions

• How does Le Chatelier's Principle help predict changes in a chemical system at equilibrium when external conditions are altered?
  • Le Chatelier's Principle states that if a system at equilibrium experiences a change in concentration, temperature, or pressure, it will shift in a direction that counteracts that change. For example, if the concentration of reactants is increased, the system will shift toward the products to re-establish equilibrium. This principle is vital for understanding how to manipulate reactions for desired outcomes by adjusting external conditions.
• Discuss the relationship between Gibbs free energy and equilibrium, specifically focusing on how Gibbs free energy indicates spontaneity.
  • Gibbs free energy is directly linked to equilibrium as it helps determine whether a reaction is spontaneous or not. A negative Gibbs free energy change indicates that a reaction can proceed spontaneously toward equilibrium. At equilibrium itself, Gibbs free energy reaches a minimum value because the system has balanced both forward and reverse reactions. Thus, understanding Gibbs free energy allows chemists to predict the favorability of reaching equilibrium.
• Evaluate how varying concentrations of reactants and products influence the position of equilibrium and overall reaction dynamics.
  • Varying concentrations of reactants or products significantly influence where equilibrium lies in a reaction. Increasing reactant concentration typically drives the reaction toward product formation, while increasing product concentration shifts it back toward reactants. This dynamic interplay means that by altering concentrations, chemists can control reaction rates and yields. Evaluating these changes allows for better predictions about the behavior of chemical systems under different scenarios.

Related terms

Le Chatelier's Principle:

A principle stating that if an external change is applied to a system at equilibrium, the system will adjust to counteract that change and re-establish equilibrium.

Gibbs Free Energy:

A thermodynamic potential that indicates the spontaneity of a process at constant temperature and pressure, where negative values imply spontaneous reactions toward equilibrium.

Reaction Quotient (Q): A ratio that compares the concentrations of products to reactants at any point in a reaction, helping to predict the direction a reaction will proceed to reach equilibrium.