WAEC Chemistry 2015 Paper

Concept:An amphoteric oxide reacts with both acids and bases to form salt and water.Common examples are $\mathrm{BeO}$, $\mathrm{Al_2O_3}$, $\mathrm{ZnO}$, $\mathrm{SnO}$, and $\mathrm{PbO}$.Explanation:In option A, $\mathrm{BeO}$ is amphoteric, but $\mathrm{MgO}$ is basic.In option B, both $\mathrm{Na_2O}$ and $\mathrm{K_2O}$ are strongly basic oxides.In option C, $\mathrm{B_2O_3}$ is acidic, while $\mathrm{Al_2O_3}$ is amphoteric.In option D, $\mathrm{SiO_2}$ is acidic, while $\mathrm{PbO}$ is amphoteric.Thus, no listed pair contains two elements that both form amphoteric oxides.Answer:None of the given options.