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Unformatted text preview: es independently. The other variable is then determined
by the equilibrium condition.
When three phases are in equilibrium, as at the triple point, the number of
degrees of freedom drops to zero. Therefore, the triple point is a unique point for
the system. In some cases, as in the case of sulfur, multiple triple points are
present (see Fig. 6.1). Each of these are unique points with zero degree of
Determining the number of components in a system is not a trivial task. We
may make up a formula for this as follows:
c = n – e – o,
where c is the number of components, n is the number of chemical species present,
e is the number of equilibria between them, and o represents any other
relationships that may determine the relative amount of one species with respect to
another. See Section 6.1 to see applications of these ideas.
Examples: 6.1, 6.2, Problems: 6.1, 6.3, 6.4–6.6. 6.3. Binary systems involving vapor:
Liquid-vapor systems consisting of two components are commonly
represented in pressure-composition diagrams at fixed temperature, or
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