The cation which forms a white precipitate soluble in excess, in both sodium hydroxide and ammonia solution is ____________
Explanation
With sodium hydroxide \(\mathrm{Ca}^{2+}\) forms a dirty white precipitate which is insoluble in excess sodium hydroxide solution. If the white precipitate dissolves on addition of excess \(\mathrm{NaOH}\), it can be \(\mathrm{Zn}^{2+}, \mathrm{Pb}^{2+}\) or \(\mathrm{Al}^{3+}\). If a white gelatinous precipitate which is insoluble in excess ammonia solution is produced, it is either \(\mathrm{Pb}^{2+}\) or \(\mathrm{Al}^{\beta+}\). If the precipitate is soluble in excess ammonia solution, it is \(\mathrm{Zn}^{2+}\).
