Which of the following hydroxides is not readily soluble in water?

Among the given options, calcium hydroxide (Ca(OH)\(_2\)) is not readily soluble in water. When an ionic compound dissolves in water, its constituent ions separate and become surrounded by water molecules in a process called hydration. The solubility of a compound depends on the strength of the attractive forces between the ions in the compound and the water molecules. Calcium hydroxide is an ionic compound composed of calcium ions (Ca\(^{2+}\)) and hydroxide ions (OH\(^-\)). When calcium hydroxide dissolves in water, it undergoes a dissociation reaction, releasing calcium ions and hydroxide ions into the solution: Ca(OH)2 (s) → Ca\(^{2+}\) (aq) + 2OH\(^-\) (aq) However, calcium hydroxide is only slightly soluble in water. This means that it only dissolves to a limited extent in water and forms a suspension or a precipitate. On the other hand, NH\(_4\)OH, NaOH, and KOH are all readily soluble in water, which means they dissolve easily in water and form clear, homogeneous solutions. In summary, calcium hydroxide is not readily soluble in water, while NH\(_4\)OH, NaOH, and KOH are readily soluble in water.