Which of the following specific metal cations possesses the unique analytical property of forming a — Qualitative and Quantitative Analysis Chemistry Question

💡 Solution & Explanation

Lead ($Pb^{2+}$) belongs to both Group I and Group II. Its chloride ($PbCl_2$) has a relatively high $K_{sp}$ for a precipitate, meaning it partially precipitates in Group I with dilute $HCl$. The remaining $Pb^{2+}$ ions pass into Group II, where they precipitate completely as the extremely insoluble black sulphide ($PbS$) with $H_2S$.