Equilibrium

Definition

Equilibrium is the state in which the rates of forward and reverse processes in a reaction are equal, resulting in no net change in the concentrations of reactants and products over time. This balance means that while individual molecules are still reacting, the overall composition of the system remains constant. Equilibrium can be influenced by various factors, including temperature, pressure, and concentration, playing a crucial role in understanding both steady-state conditions and entropy changes in chemical reactions.

5 Must Know Facts For Your Next Test

1. At equilibrium, the concentrations of reactants and products do not change over time, even though molecular reactions continue to occur.
2. The position of equilibrium can shift in response to changes in concentration, temperature, or pressure, as described by Le Chatelier's Principle.
3. Equilibrium constants ($$K$$) quantitatively describe the ratio of product concentrations to reactant concentrations at equilibrium for a reversible reaction.
4. In reactions involving gases, increasing pressure shifts equilibrium towards the side with fewer moles of gas, while decreasing pressure favors the side with more moles.
5. Entropy changes in chemical reactions can help predict how equilibrium will be affected; reactions that lead to increased disorder typically favor product formation.

Review Questions

• How does Le Chatelier's Principle relate to shifts in equilibrium when external conditions are altered?
  • Le Chatelier's Principle states that when a system at equilibrium experiences a change in concentration, temperature, or pressure, the system will adjust itself to counteract that change. For instance, if the concentration of a reactant is increased, the system will shift toward producing more products to restore balance. This principle helps predict how an equilibrium will respond under different conditions, making it essential for understanding dynamic systems.
• Explain how entropy changes are associated with equilibrium in chemical reactions and their significance.
  • Entropy changes are crucial for understanding how chemical reactions reach equilibrium. When a reaction proceeds towards products that have higher entropy, it often indicates greater disorder or randomness in the system. As reactions move toward this higher entropy state, they may favor product formation at equilibrium. Thus, analyzing entropy changes allows for predictions about reaction spontaneity and shifts in equilibrium position.
• Evaluate the importance of Gibbs Free Energy in determining the position of equilibrium and predicting reaction spontaneity.
  • Gibbs Free Energy is vital for determining whether a reaction will proceed spontaneously toward products or maintain its equilibrium position. At equilibrium, Gibbs Free Energy reaches its minimum value under constant temperature and pressure. If the change in Gibbs Free Energy ($$ ext{Δ}G$$) is negative, the reaction is spontaneous toward products; if positive, it favors reactants. Understanding this relationship provides insights into how various factors impact equilibrium and helps predict the direction of chemical processes.

Related terms

Dynamic Equilibrium:

A state where the forward and reverse reactions occur at the same rate, keeping concentrations of reactants and products constant while allowing ongoing reactions.

Le Chatelier's Principle:

A principle stating that if a dynamic equilibrium is disturbed by changing conditions, the system will adjust to counteract that change and restore a new equilibrium.

Gibbs Free Energy:

A thermodynamic potential that indicates the spontaneity of a process; a system at equilibrium has a Gibbs Free Energy minimum under constant temperature and pressure.