Test with Iodide Ions by Whatsapp Cikgu Kwee now! Test with Iodide Ions Iodide ions will form precipitate with lead(II) ions and copper(II) ions.However, in SPM you only need to know the reaction between lead(II) ions and iodide ions.The yellow precipitate formed will dissolve in hot water.Pb2+ + 2I– → PbI2KINa+–Ca2+–Mg2+–Al3+–Zn2+–Pb2+Yellow precipitate. Dissolve in hot waterFe2+–Fe3+A red brown solution formed.Cu2+White precipitate form in brown solutionNH4+– Whatsapp Cikgu Kwee now!