Chemistry - Complete d-block Question with Solution | TestHub

Mercury(II) sulfide (HgS) is known for its extreme insolubility. While many metal sulfides react with hot and dilute nitric acid ($HN{O}_3$) to form soluble nitrates and sulfur, HgS is an exception. Its high lattice energy and strong covalent character contribute to its resistance to dissolution in common acids, including hot and dilute $HN{O}_3$. It typically requires aqua regia (a mixture of concentrated nitric acid and hydrochloric acid) to dissolve.

The final answer is $\boxed{A}$