The evolution of a red-brown gas on heating a salt with K2Cr2O7 and concentrated H2SO4 can arise fro — Qualitative and Quantitative Analysis Chemistry Question

💡 Solution & Explanation

Step 1: A chloride salt that releases a gas with an alkali solution is an ammonium salt (A = NH4Cl). The released gas is ammonia (B = NH3). Step 2: Ammonia reacts with Nessler's reagent (alkaline potassium tetraiodomercurate, K2[HgI4]) to form a brown precipitate (C). Step 3: The chemical formula of this brown precipitate (Iodide of Millon's base) is HgO.Hg(NH2)I. Therefore, the set of compounds is NH4Cl, NH3, and HgO.Hg(NH2)I, matching option (d).