Chemical Thermodynamics

Each list begins with basic conceptual vocabulary you need to know for MCAT questions and proceeds to advanced terms that might appear in context in MCAT passages. The terms are links to Wikipedia articles.
Equilibrium constant
The equilibrium constant is the reaction quotient describing the state in which the chemical activities or concentrations of the reactants and products have no net change over time.
Spontaneous process
A spontaneous process is a chemical reaction in which a system releases free energy and moves to a lower, more thermodynamically stable, energy state.
Chemical thermodynamics
Chemical thermodynamics is the mathematical study of the interrelation of heat and work with chemical reactions or with a physical change of state within the confines of the laws of thermodynamics.
Thermodynamic free energy
The term thermodynamic free energy is a measure of the amount of work that can be extracted from a system.
Endergonic reaction
An endergonic reaction (also called an unfavorable reaction or a nonspontaneous reaction) is a chemical reaction in which the standard change in free energy is positive.
Exergonic reaction
An exergonic reaction is a chemical reaction where the variation of Gibbs free energy is negative.
Le Chatelier's principle
Le Chatelier's principle states that if a chemical system at equilibrium experiences a change in concentration, temperature, volume, or total pressure, the equilibrium will shift in order to partially counter-act the imposed change.
Gibbs free energy
The Gibbs free energy is a thermodynamic potential which measures the useful or process-initiating work obtainable from an isothermal, isobaric thermodynamic system.
Dynamic equilibrium
A dynamic equilibrium occurs when two reversible processes proceed at the same rate.
Reaction quotient
The reaction quotient is a quantitative measure of the extent of reaction, the relative proportion of products and reactants present in the reaction mixture at some instant of time.
Entropy of mixing
The entropy of mixing is the change in the entropy when two different chemical substances or components are mixed.
Activity in chemistry is a measure of how different molecules in a non-ideal gas or solution interact with each other, extending the idea of concentration to more complex systems.
Activity coefficient
An activity coefficient is a factor used in thermodynamics to account for deviations from ideal behaviour in a mixture of chemical substances.
Thermodynamic potential
Thermodynamic potentials are parameters associated with a thermodynamic system and have the dimensions of energy which describe the capacity for spontaneous change in a thermodynamic system when it is subjected to certain constraints.
Chemical potential
The chemical potential of a thermodynamic system is the amount by which the energy of the system would change if an additional particle were introduced, with the entropy and volume held fixed.
Fugacity is a measure of chemical potential in the form of 'adjusted pressure' directly related to the tendency of a substance to prefer one phase over another.
Thermodynamic limit
The thermodynamic limit is reached as the number of particles in a system approaches infinity and the thermodynamic behavior of a system is asymptotically approximated by the results of statistical mechanics.
Helmholtz free energy
The Helmholtz free energy is a thermodynamic potential which measures the useful work obtainable from a closed thermodynamic system at a constant temperature.
Gibbs paradox
The Gibbs paradox, also known as mixing paradox, involves the discontinuous nature of the entropy of mixing.
Gibbs' phase rule
The Gibbs' phase rule relates the number of phases present in equilibrium, the number of degrees of freedom, pressure and composition of the phases present, and the number of chemical components required to describe the system.
Non-equilibrium thermodynamics
Non-equilibrium thermodynamics is a branch of thermodynamics concerned with studying time-dependent thermodynamic systems, irreversible transformations and open systems.
Dissipative system
A dissipative system is a thermodynamically open system which is operating far from thermodynamic equilibrium in an environment with which it exchanges energy, matter and/or entropy.
Debye-Hückel equation
The Debye-Hückel limiting law provides a method for obtaining activity coefficients for solutions that contain ionic solutes.
Van't Hoff equation
The Van't Hoff equation in chemical thermodynamics relates the change in temperature to the change in the equilibrium constant given the enthalpy change.
Gibbs-Duhem equation
The Gibbs-Duhem equation in thermodynamics describes the relationship between changes in chemical potential for components in a thermodynamical system, showing that in thermodynamics intensive properties are not independent but related.

The Integrated MCAT Course is a trademark of Wisebridge Learning Systems. Unless otherwise specified, the works of the Integrated Course are published under a Creative Commons Attribution NonCommercial ShareAlike License. MCAT is a registered trademark of the Association of American Medical Colleges, which does not endorse the Integrated MCAT Course. The Integrated MCAT Course offers our customers no guarantees regarding eventual performance on the MCAT.