WAEC Chemistry 2025 Paper

Concept:Double decomposition is a metathesis reaction in which two soluble salts exchange ions to form at least one insoluble salt, known as a precipitate.Explanation:Silver chloride, $\mathrm{AgCl}$, is insoluble in water. Thus, it can be prepared by double decomposition from two soluble salts: silver trioxonitrate (V), $\mathrm{AgNO}_3$, and sodium chloride, $\mathrm{NaCl}$.The reaction is:$$\mathrm{AgNO_3(aq)} + \mathrm{NaCl(aq)} \rightarrow \mathrm{AgCl(s)} + \mathrm{NaNO_3(aq)}$$Here, $\mathrm{Ag^+}$ and $\mathrm{Cl^-}$ combine to form the white precipitate $\mathrm{AgCl}$, while $\mathrm{Na^+}$ and $\mathrm{NO_3^-}$ stay dissolved.The other listed salts are soluble in water, so they are not typically prepared by this precipitation or double decomposition method.Answer:D. silver chloride.