In the standard qualitative analysis framework, gas is passed through a dilute solution to precipita — Qualitative and Quantitative Analysis Chemistry Question

💡 Solution & Explanation

Group II cations are those with sufficiently low $K_{sp}$ for their sulphides to precipitate in an acidic medium. The cations $Pb^{2+}$ (also in Group I but partially passes to II), $Cu^{2+}, As^{3+}, Sb^{3+}, Bi^{3+}, Sn^{2+},$ and $Cd^{2+}$ belong to Group II (Total = 7). The cations $Ni^{2+}$ and $Zn^{2+}$ belong to Group IV and require a basic medium ($NH_4OH$) to precipitate as sulphides.