Question

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

Answer 1

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.