Example 2.1

In the viscinity of the triple point, the vapour pressure of liquid ammonia (in atmosphere) is represented by

This is the equation of liquid vapour boundary curve in a p-T diagram. Similarly, the vapour pressure of solid ammonia is given by
(a) What is the temperature and pressure at the triple point?
(b) What are the latent heat of sublimation and vaporization?
(c) What is the latent heat of fusion at the triple point?

Solution

At the triple point, the saturated solid line & saturated liquid lines meet.

Again,
Clausius-Clayperon equation rettuces to

Lsub=latent heat of sublimation

The vapour pressure of solid ammonia is given by

The vapour pressure of liquid ammonia is given by,