WAEC Chemistry 2024 Paper

Concept:Gases that are less dense than air are collected by downward displacement of air.Explanation:Downward displacement of air is used for gases that are lighter than air.Hydrogen ($\mathrm{H}_2$) has a very low density and rises upward, so it can be collected in an inverted container.Chlorine ($\mathrm{Cl}_2$), hydrogen chloride ($\mathrm{HCl}$), and sulphur(IV) oxide ($\mathrm{SO}_2$) are all denser than air.Heavier gases are collected by upward displacement of air, not downward displacement.Therefore, among the options, only hydrogen is suitable for downward displacement of air.Answer:B. Hydrogen