WAEC Chemistry 2010 Paper

Concept:Basic oxides are typically metal oxides that react with acids to form salts and water.Explanation:$\mathrm{NO}_2$ is a non-metal oxide, so it is acidic in nature.$\mathrm{SO}_2$ is also a non-metal oxide and dissolves in water to form an acidic solution.$\mathrm{Al}_2\mathrm{O}_3$ is amphoteric because it can react with both acids and bases.$\mathrm{CaO}$ is a metal oxide.It reacts with water to give $\mathrm{Ca(OH)}_2$, which is a strong base.Hence, $\mathrm{CaO}$ is the basic oxide among the given options.Answer:D. $\mathrm{CaO}$