Identify the cation in each of the following cases:
(a) Ammonium hydroxide solution when added to Solution B gives a white precipitate which does not dissolve in excess of ammonium hydroxide solution.
(b) Sodium hydroxide solution when added to Solution C gives a white precipitate which is insoluble in excess of sodium hydroxide solution.
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(a) Pb2+
Reason — When ammonium hydroxide solution is added to lead nitrate, it forms a chalky white precipitate of lead hydroxide [Pb(OH)2] which is insoluble in excess of ammonium hydroxide.
Pb(NO3)2 + 2NH4OH ⟶ 2NH4NO3 + Pb(OH)2
(b) Ca2+
Reason — When sodium hydroxide solution is added to calcium nitrate, a white precipitate of calcium hydroxide is obtained which is insoluble in excess of sodium hydroxide solution.
Ca(NO3)2 + 2NaOH ⟶ Ca(OH)2 ↓ + 2NaNO3