Question

How many triple points are in the phase diagram below:

Answer 1

Answer: There are 3 triple points in the given phase diagram.

Explanation: Triple point is defined as the point at which the temperature and pressure of the 3 phases are in equilibrium with each other.

In the given phase diagram, there are three points which is satisfying this definition.

Point A: At this point The monoclinic form and rhombic form have the same vapor pressure. Hence,

$Rhombic(s) \rightleftharpoons Monoclinic(s) \rightleftharpoons Vapor(g)$

Point B: At this point, the monoclinic form starts to melt. Hence,

$Rhombic(s) \rightleftharpoons Liquid(l) \rightleftharpoons Vapor(g)$

Point C: At this point, the rhombic form, monolinic form and liquid is in equilibrium. Hence,

$Rhombic(s) \rightleftharpoons Monoclinic(s) \rightleftharpoons Liquid(l)$

Hence, this system has 3 triple points.