JAMB Chemistry 2016 Paper

Concept:An alkali is a soluble base that releases hydroxide ions ($\mathrm{OH^-}$) in water.Explanation:$\mathrm{NaOH}$ is a soluble hydroxide and is a strong alkali.$\mathrm{Ca(OH)_2}$ is also a soluble hydroxide and therefore an alkali.$\mathrm{NH_3}$ dissolves in water to form an alkaline solution, so it behaves as an alkali.However, $\mathrm{Al(OH)_3}$ is insoluble and amphoteric.It can act as both a base and an acid when the need arises.Since it does not readily dissolve in water to release $\mathrm{OH^-}$ ions, it is not considered an alkali.Answer:D. $\mathrm{Al(OH)_3}$ is not an alkali.