Equilibrium (IB)

Reversible Reaction

A chemical reaction that can proceed in both forward and reverse directions.

Dynamic Equilibrium

A state in which the rates of the forward and reverse reactions are equal, resulting in no net change in concentrations.

Equilibrium Constant (Kₓ)

The ratio of the concentrations of products to reactants at equilibrium, constant at a given temperature.

Le Chatelier’s Principle

The principle stating that an equilibrium system will adjust to counter changes in concentration, temperature, or pressure.

Reaction Quotient (Q)

A measure of the relative concentrations of reactants and products at any point in a reaction.

Condition for Equilibrium

A closed system where reactants and products are contained, allowing reactions to operate without interference.

Single Arrow (→)

Indicates a non-reversible reaction that proceeds only in one direction.

Double Arrow (⇌)

Indicates a reversible reaction in a state of dynamic equilibrium.

Factors Affecting Equilibrium Position

Concentration, temperature, pressure, and the presence of catalysts.

Homogeneous Equilibrium

An equilibrium where all reactants and products are in the same phase.

Heterogeneous Equilibrium

An equilibrium where reactants and products are in different phases.

Phase Equilibrium

The state of balance between phases, such as liquid and gas, within a system.

Vapor Pressure

The pressure exerted by a gas in equilibrium with its liquid phase at a given temperature.

Catalyst

A substance that increases the rate of chemical reactions without being consumed, not affecting equilibrium position.

Exothermic Reaction

A reaction that releases heat, favoring products at lower temperatures.

Endothermic Reaction

A reaction that absorbs heat, favoring products at higher temperatures.

Effect of Temperature on Equilibrium

Changes in temperature can shift equilibrium positions and alter the value of Kc.

Effect of Pressure on Equilibrium

Changing pressure affects equilibrium in gaseous reactions based on the number of gas molecules.

Effects of Concentration Changes

Adding or removing reactants or products affects the equilibrium position but not Kc.

Equilibrium Law

At a given temperature, the expression for the equilibrium constant is determined by the stoichiometry of the balanced equation.

Kc Expression Example

For the reaction aA + bB ⇋ cC + dD, Kc = [C]^c [D]^d / [A]^a [B]^b.

Phase Changes at Equilibrium

At equilibrium, phase changes like evaporation and condensation occur at equal rates.

Impact of Doubling Coefficients

Doubling the coefficients in a reaction results in the new equilibrium constant being raised to the power of two.

Impact of Halving Coefficients

Halving the coefficients results in the equilibrium constant being the square root of the original Kc.

Direction Prediction Using Q

Comparing Q to Kc helps predict if the reaction will shift forward or backward to reach equilibrium.