The Notion of Activity in Chemistry

1st  part: The Activity in Classical Thermodynamics.- Thermodynamic systems.- Gibbs and Helmhotz energies.- Escaping tendency and molar Gibbs energy.- Partial molar properties.- Chemical potential or partial molar Gibbs energy.- An overview of the notion of activity.- The concept of fugacity.- Ideal solutions.- Definitions of the activity.- Activity of a gaz.- Activities of non- electrolytes in solutions.- Activities of electrolytes: definitions.- Determination of the activity of non-electrolytes.- Determination of the activity of electrolytes.- Debye and Hückel 's relations.- Excess Gibbs energies and activities.- Chemical  equilibrium  constants : activities and  Gibbs energies of reactions.- Derivation of thermodynamic equilibrium constants- pH and its measure.- General principles of calculations of ionic species concentrations in solutions involving  activities .- 2nd  part: The Activity in Statistical Thermodynamics.- Statistical thermodynamics in brief.- Concept of ensembles and postulates.- The canonical ensemble: notion of distribution.- Thermodynamic quantities in the framework of the canonical ensemble.- Other ensembles .- Systems of molecules and subsystems  independent  distinguishable and      "indistinguishable".- Perfect gases.- Classical statistical mechanics- Notion of configuration -  Classical canonical partition function.- The configurational  partition function - Molecular distribution functions.- The radial distribution function.- Radial distribution function and  thermodynamic quantities- calculations of the internal energy and of the pressure of a system.- Radial distribution function and calculation of the isothermal compressibility coefficient of a system.- The chemical potential and the radial distribution function: General formal introduction of the activity and  of the  activity coefficient.- Imperfect gases - The virial coefficients in terms of interaction

Jean-Louis Burgot is a retired Professor of analytical chemistry in Rennes, France.