[UPSC CSE 2019] Thermodynamics (Q51, 15M)

What is Gibbs phase rule? Find the values of degrees of freedom when

(i) only the liquid \mathrm{CO_2} is in equilibrium with the gaseous \mathrm{CO_2}.

(ii) water is in the vapour-liquid saturation region.

(iii) water is in a single-phase region.

(iv) water is at the triple point.