Question

Answer the following questions based on the P–T phase diagram of CO₂:

Describe qualitatively the changes in a given mass of solid CO₂ at 10 atm pressure and temperature –65 °C as it is heated up to room temperature at constant pressure.

Answer 1

The fusion and boiling points are given by the intersection point where this parallel line cuts the fusion and vaporisation curves.

Answer 2

When the solid CO₂ at – 65 °C is heated at 10 atm pressure, it is first converted into liquid. A further increase in its temperature brings it into the vapour phase. If a horizontal line at P = 10 atm is drawn parallel to the T-axis, then the points of intersection of line with the fusion and vaporization curve give the fusion and boiling points at 10 atm.