When H2S is passed through a solution containing [Cu(CN)4]3- and [Cd(CN)4]2- ions, only cadmium prec — Qualitative and Quantitative Analysis Chemistry Question

💡 Solution & Explanation

Step 1: Cobalt(II) chloride hexahydrate (CoCl2.6H2O) exists as reddish-pink crystals. Step 2: Upon heating, it loses its water of crystallization to form anhydrous cobalt(II) chloride, which has a deep blue color: CoCl2.6H2O (pink) --Δ--> CoCl2 (blue) + 6H2O (vapour). Step 3: When water is added back to the blue anhydrous residue, it readily rehydrates to restore the pink hexahydrate, CoCl2.6H2O. This matches option (c).