WAEC Chemistry 2021 Paper

Concept:Double displacement of two soluble salts can form an insoluble lead salt as a precipitate.Explanation:Adding copper(II) sulfate solution to lead(II) nitrate solution causes the cations and anions to exchange.The balanced equation for the reaction is:$\mathrm{CuSO_4(aq) + Pb(NO_3)_2(aq) \rightarrow PbSO_4(s) + Cu(NO_3)_2(aq)}$Here, $\mathrm{PbSO_4}$ is sparingly soluble in water and appears as a white precipitate.The other product, $\mathrm{Cu(NO_3)_2}$, dissolves completely and gives a blue colour to the solution due to $\mathrm{Cu^{2+}}$ ions.As a result, the change is clearly visible and the solution is not colourless.The precipitate is white, not blue, so option B is incorrect.Thus, the only correct statement is that a white precipitate is formed.Answer:D. a white precipitate would be formed