Which of the following is not soluble in hot and conc. HNO3? — Qualitative and Quantitative Analysis Chemistry Question

💡 Solution & Explanation

Step 1: Sulfides of Group II and Group IV cations have varying solubilities in nitric acid. Step 2: PbS, NiS, and CuS dissolve in hot concentrated HNO3 by being oxidized to their soluble nitrates along with the formation of sulfur. However, mercuric sulfide (HgS) is extremely insoluble (Ksp ~ 10^-52) and does not dissolve in concentrated HNO3 alone. Step 3: It requires aqua-regia (mixture of HCl and HNO3) to dissolve HgS through a combination of oxidation and complexation. Hence, HgS is not soluble in hot and conc. HNO3, matching option (d).