JAMB Chemistry 2010 Paper

Concept:Organic compounds that form hydrogen bonds with water are very soluble.Explanation:Ethanoic acid, $\mathrm{CH}_{3}\mathrm{COOH}$, is a carboxylic acid with a polar hydroxyl group.This group forms strong hydrogen bonds with water molecules.As a result, ethanoic acid mixes completely with water in all proportions.The other compounds are hydrocarbons or esters with little or no polarity.Ethene, $\mathrm{C}_{2}\mathrm{H}_{4}$, and ethyne, $\mathrm{C}_{2}\mathrm{H}_{2}$, are non-polar gases and are almost insoluble in water.Ethyl ethanoate, $\mathrm{CH}_{3}\mathrm{COOC}_{2}\mathrm{H}_{5}$, is only slightly soluble because it is an ester.Therefore, ethanoic acid is the only option that is very soluble in water.Answer:$\mathrm{CH}_{3}\mathrm{COOH}$ (Option A)