Page 25 - Chemical equilibria Volume 4

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Physico-Chemical

Transformations and Equilibria

A physico-chemical transformation of a system is the modification of the
nature of its components under the influence of external stresses.

1.1. Characteristic parameters of physico-chemical transformations

A component is characterized by its chemical nature and by the phase to
which it belongs. We can distinguish two types of physico-chemical
transformations:
– physical transformations where there is no alteration of the chemical
nature of the species but there is a modification of their phases;
– chemical transformations or reactions, where there is a modification of
the chemical nature of the species present, and where that modification may
or may not be accompanied by a phase change.

1.1.1. Balance equation of a transformation

Generally, a transformation is represented by its balance equation, which
specifies the initial components, present before the transformation, and the
end components. Symbolically, such a balance equation is written in the
form:

0 = ∑ ν i A i [1R.1]
i

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