WAEC Chemistry 2019 Paper

Concept:The bleaching action of chlorine is based on a chemical change that destroys the colour of a substance.Explanation:Chlorine ($\mathrm{Cl}_2$) reacts with water to form hydrochloric acid ($\mathrm{HCl}$) and hypochlorous acid, also called oxochlorate(I) acid ($\mathrm{HOCl}$).The hypochlorous acid decomposes easily to release nascent oxygen.This nascent oxygen combines with the coloured material and oxidises it to a colourless compound.Thus, the coloured substance loses its colour because it has been oxidised.This is why the process is described as oxidation, not hydration, hydrolysis, or reduction.Answer:D. Oxidation