WAEC Chemistry 2016 Paper

Concept:Boiling point increases with the strength of intermolecular hydrogen bonding.Explanation:The given compounds all show hydrogen bonding. Their boiling points depend on how strongly their molecules attract one another. Ammonia ($\mathrm{NH}_3$) boils at $-33.34^\circ\mathrm{C}$. Hydrogen fluoride ($\mathrm{HF}$) boils at $19.5^\circ\mathrm{C}$. Water ($\mathrm{H}_2\mathrm{O}$) boils at $100^\circ\mathrm{C}$. Arranging these from the lowest to the highest boiling point gives: $\mathrm{NH}_3 < \mathrm{HF} < \mathrm{H}_2\mathrm{O}$.Answer:D. $\mathrm{NH}_3 < \mathrm{HF} < \mathrm{H}_2\mathrm{O}$