Principle of maximum work

Whilst this principle is undoubtedly applicable to the great majority of chemical actions under ordinary conditions, it is subject to numerous exceptions, and cannot therefore be taken (as its authors originally intended) as a secure basis for theoretical reasoning on the connection between thermal effect and chemical affinity.

As the principle was abandoned even by its authors, it is now only of historical importance, although for many years it exerted considerable influence on thermochemical research.

Historically, the "free energy" is a more advanced and accurate replacement for the thermochemistry term “affinity” used by chemists of olden days to describe the “force” that caused chemical reactions.

Chemists called the ‘force’ that caused chemical reactions affinity, but it lacked a clear definition.

[2] During the entire 18th century, the dominant view in regard to heat and light was that put forward by Isaac Newton, called the “Newtonian hypothesis”, which stated that light and heat are forms of matter attracted or repelled by other forms of matter, with forces analogous to gravitation or to chemical affinity.

With the development of the first two laws of thermodynamics in the 1850s and 60s, heats of reaction and the work associated with these processes were given a more accurate mathematical basis.

(If it were an irreversible heat source, the entropy increase would be larger than δQ/T) Define: We may now make the following statements Eliminating

gives the following equation: When the primary system is reversible, the equality will hold and the amount of work delivered will be a maximum.