What type of phase diagram should I draw if more than one pure component present?

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Feb 18, 2016

If there are only 2 components, draw the phase diagram of binary solutions. A 2D plot requires some variables to be held constant.

Explanation:

Recall the Phase Rule:

#F = C - P + 2#

#F#: the number of degree of freedom (number of independent intensive variables that are needed to specify a state)

#C#: the number of components (#C = 2# for binary systems)

#P#: the number of phases

If the binary system (#C = 2#) is in a single phase (#P = 1#), then #F = 3#, i.e. 3 variables; pressure, temperature and the mole fraction of either component, are needed to describe the system.

In order to plot a 2D phase diagram, either #p# or #T# needs to be fixed, so only the other two variables are shown by the vertical and the horizontal axes.

Two types of phase diagrams are commonly used: the pressure–composition phase diagrams and the temperature–composition phase diagrams.

Below is a pressure-composition phase diagram of an ideal solution with 2 components, A and B.

www.chemguide.co.uk

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