WAEC Chemistry 2016 Paper

Concept:Concentrated tetraoxosulphate(VI) acid, $\mathrm{H}_2\mathrm{SO}_4$, acts as a dehydrating agent and converts alkanols into alkenes.Explanation:When an alkanol is heated with concentrated $\mathrm{H}_2\mathrm{SO}_4$, dehydration occurs.A molecule of water is removed from the alkanol.This elimination reaction forms a carbon-carbon double bond, producing an alkene.A general example is:$$\mathrm{R{-}CH_2{-}CH_2OH} \xrightarrow{\text{conc. }\mathrm{H}_2\mathrm{SO}_4} \mathrm{R{-}CH{=}CH_2} + \mathrm{H}_2\mathrm{O}$$For ethanol, the reaction is:$$\mathrm{C}_2\mathrm{H}_5\mathrm{OH} \xrightarrow{\text{conc. }\mathrm{H}_2\mathrm{SO}_4} \mathrm{C}_2\mathrm{H}_4 + \mathrm{H}_2\mathrm{O}$$Since compound X gives an alkene under these conditions, X must belong to the alkanol family.Alkanes, alkanoates, and alkynes do not undergo this dehydration to form alkenes easily.Answer:B. Alkanol