Which of the following precipitate is soluble in excess of NH3 solution ? — Qualitative and Quantitative Analysis Chemistry Question

💡 Solution & Explanation

Step 1: Solubility of precipitates in ammonia depends on their ability to form stable, soluble ammine coordination complexes. Step 2: Nickel(II) hydroxide, Ni(OH)2, reacts with excess ammonia to form the highly stable, soluble hexaamminenickel(II) complex: Ni(OH)2 + 6 NH3 ---> [Ni(NH3)6]^2+ + 2 OH^-, yielding a characteristic deep blue solution. Step 3: In contrast, Pb(OH)2, Fe(OH)2, and highly stable Ag2S do not dissolve in excess ammonia. Hence, option (c) is correct.