Chemical-engineering thermodynamics: definitions and fundamental laws

In contrast to energy thermodynamics, the term "chemical thermodynamics" should be understood as the branch of the broad field of thermodynamics devoted to the study of the properties of matter, and in particular its energetic properties and phase equilibria.

In this article, we present the basic concepts, definitions, and fundamental relationships in chemical thermodynamics, and more specifically:

• the vocabulary of the field, with an emphasis on the concept of thermodynamic states;

• the mathematical relationships and methods used to express the derivatives of thermodynamic variables, define partial molar quantities and relate them to total molar quantities, and relate the various properties of matter to one another;

• the postulates of thermodynamics, from the zeroth law to the third law; particular attention is given to the definition of entropy and its physical interpretation;

• the concept of thermodynamic equilibrium, along with a discussion of the criteria for local mechanical and thermal instabilities.

This article has been designed to provide readers with all the foundational concepts necessary for thermodynamic analyses of processes in the chemical industry or energy production.