Question

the electron cloud of hf is smaller than that of f₂, however, hf has a much higher boiling point than f₂ has. which of the following explains how the dispersion - force model of intermolecular attraction does not account for the unusually high boiling point of hf?
a f₂ is soluble in water, whereas hf is insoluble in water.
b the f₂ molecule has a greater mass than the hf molecule has.
c liquid f₂ has weak dispersion force attractions between its molecules, whereas liquid hf has strong ionic interactions between h⁺ and f⁻ ions.
d liquid f₂ has weak dispersion force attractions between its molecules, whereas liquid hf has both weak dispersion force attractions and hydrogen bonding interactions between its molecules.

Explanation:

• Option A: Solubility in water is not related to boiling point.
• Option B: Mass of molecules is related to dispersion forces. But HF has hydrogen bonding which is stronger.
• Option C: HF is a covalent compound, not ionic.
• Option D: HF has hydrogen bonding (strong intermolecular force) in addition to weak dispersion forces. F₂ only has weak dispersion forces. Stronger intermolecular forces lead to higher boiling point.

Answer:

D. Liquid F₂ has weak dispersion force attractions between its molecules, whereas liquid HF has both weak dispersion force attractions and hydrogen bonding interactions between its molecules.