WAEC Chemistry 2020 Paper

Concept:The solubility of hydroxides in water depends on the metal cation present.Explanation:Hydroxides of group 1 metals such as $\mathrm{NaOH}$ and $\mathrm{KOH}$ are highly soluble in water.Ammonium hydroxide, $\mathrm{NH_4OH}$, is also readily soluble and forms a weak base.In contrast, calcium hydroxide, $\mathrm{Ca(OH)_2}$, is only sparingly soluble in water.Therefore, among the given options, $\mathrm{Ca(OH)_2}$ is the hydroxide that is not readily soluble.Answer:B. $\mathrm{Ca(OH)}_2$