Three crystalline solids, P, Q, and R, are each maintained at 30∘C in identical closed containers. The measured equilibrium vapour pressures are shown.
Solid
Vapour pressure (torr)
P
120
Q
2.0
R
0.03
Assume each solid is pure and thermally stable at 30∘C.
(a) Rank the three solids from lowest to highest normal boiling point. Justify your ranking with reference to the data provided.
(b) For each solid, propose the most likely type of crystalline solid (ionic, covalent network, molecular, or metallic). Support each choice with two distinct pieces of evidence grounded in the data or periodic trends.
(c) Predict which solid has the greatest lattice (or cohesive) energy and explain how your prediction is consistent with the observed vapour pressures.