Thermodynamic background
Start with the big picture
At constant temperature and pressure, equilibrium corresponds to a minimum in Gibbs free energy, with ΔG = 0; the sign of ΔG indicates the favored reaction direction away from equilibrium. The relationship ΔG = ΔG° + RT ln Q connects reaction conditions to the equilibrium constant, while activities provide a general way to express component contributions. Concentrations and partial pressures serve as ideal-system approximations, whereas fugacity and activity coefficients address non-ideal behavior. Enthalpy helps explain how K changes with temperature through the van’t Hoff relationship, and entropy contributes to the overall thermodynamic balance. Chemical potential and extent of reaction offer component-level and composition-based perspectives on equilibrium. Standard states, pressure effects, and the phase rule complete the broader framework.
What you'll learn
- Relate Gibbs free-energy change to reaction direction and equilibrium.
- Explain how ΔG°, Q, and K are connected.
- Distinguish activities from ideal concentration or pressure approximations.
- Describe how enthalpy and temperature influence the equilibrium constant.
- Identify the roles of chemical potential, standard states, and phase rule.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
