International Baccalaureate IB Chemistry
5.3.1 Dynamic equilibrium
A state of dynamic equilibrium is reached in a closed system when the rates of forward and backward reactions are equal. Describe the characteristics of a physical and chemical system at equilibrium.
5.3.2 Equilibrium constant expression
The equilibrium law describes how the equilibrium constant, $K$, can be determined from the stoichiometry of a reaction. Deduce the equilibrium constant expression from an equation for a homogeneous reaction.
5.3.3 Magnitude of K and temperature dependence
The magnitude of the equilibrium constant indicates the extent of a reaction at equilibrium and is temperature dependent. Determine the relationships between K values for reactions that are the reverse of each other at the same temperature.
5.3.4 Le Châtelier’s principle
Le Châtelier’s principle enables the prediction of the qualitative effects of changes in concentration, temperature and pressure to a system at equilibrium. Apply Le Châtelier’s principle to predict and explain responses to changes of systems at equilibrium.
5.3.5 Reaction quotient Q
The reaction quotient, Q, is calculated using the equilibrium expression with non‑equilibrium concentrations of reactants and products. Calculate Q from the concentrations of reactants and products at a particular time, and determine the direction in which the reaction will proceed to reach equilibrium.
5.3.6 Using the equilibrium law for calculations
Solve problems involving values of K and initial and equilibrium concentrations of the components of an equilibrium mixture.
5.3.7 Equilibrium constant and Gibbs energy
The equilibrium constant and Gibbs energy change, $ \Delta G $, can both be used to measure the position of an equilibrium reaction. Calculate $ \Delta G^\circ = -RT \ln K $.