Page 129 - Chemical equilibria Volume 4

4

Determination of the Values

Associated with Reactions –

Equilibrium Calculations

The objective of this chapter is, by experimentation or computation, on
the basis of the values of the main properties, to determine the value of the
equilibrium constant of a reaction, or, which is the same thing by virtue of
relation [4.2], that of the standard molar Gibbs energy associated with the
reaction in question.

We shall then examine the use of those values to calculate complex
equilibria, enabling us to define domains of stability of the phases and the
compounds, domains of predominance of components, and to serve the
ultimate goal of a transformation within the system.
In this chapter, we only look at molecular reactions. Ionic equilibria will
be studied in Volume 6 of this Set of books.

4.1. Reminders of a few thermodynamic relations

In this section, we shall establish a certain number of thermodynamic
relations specific to the reactions, which will be useful to us in this chapter,
particularly, for calculating the values.

Remember that every time we attempt to determine an equilibrium
constant, we need to begin by choosing the constant in question (see section
3.1.2) and the reference states. Remember that as a reference, we can choose

Chemical Equilibria, First Edition. Michel Soustelle.
© ISTE Ltd 2015. Published by ISTE Ltd and John Wiley & Sons, Inc.