Question

substance normal boiling point hf 293 k f₂ 85 k 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:

Dispersion forces are weak and depend on the size of the electron - cloud. $F_2$ has only dispersion forces between its non - polar molecules. HF, in addition to weak dispersion forces, has strong hydrogen bonding due to the highly electronegative fluorine atom bonded to hydrogen. This hydrogen bonding significantly increases the boiling point of HF compared to $F_2$. Option A is about solubility, not boiling point. Option B, mass is not the main factor here. Option C is wrong as HF is covalent and does not have strong ionic interactions in the liquid state.

Answer:

D. Liquid $F_2$ has weak dispersion force attractions between its molecules, whereas liquid HF has both weak dispersion force attractions and hydrogen bonding interactions between its molecules.