WAEC Chemistry 2021 Paper

Concept:Chlorine gas is a strong oxidising agent, so it must be removed by a reducing agent that can destroy its harmful nature.Acidified $\mathrm{FeSO_4}$ contains $\mathrm{Fe^{2+}}$ ions, which readily donate electrons to chlorine.Explanation:Humid air provides moisture, allowing chlorine gas to dissolve and participate in chemical reactions.Sprinkling acidified $\mathrm{FeSO_4}$ solution brings $\mathrm{Fe^{2+}}$ ions into contact with the dissolved chlorine.The $\mathrm{Fe^{2+}}$ ions are oxidised to $\mathrm{Fe^{3+}}$, while chlorine is reduced to safe chloride ions.The balanced ionic reaction is:$$2\mathrm{Fe^{2+}} + \mathrm{Cl_2} \rightarrow 2\mathrm{Fe^{3+}} + 2\mathrm{Cl^-}$$This converts toxic chlorine into harmless chloride, so the polluted air is restored.Options like $\mathrm{MnO_2}$, acidified $\mathrm{KMnO_4}$, and saturated $\mathrm{NaCl}$ are oxidising agents or unreactive mixtures, so they cannot deactivate chlorine effectively.Answer:C. acidified $\mathrm{FeSO_4}$