Which of the following sulphides dissolve in dilute HCl? — Qualitative and Quantitative Analysis Chemistry Question

💡 Solution & Explanation

Step 1: The black precipitate A is bismuth(III) sulfide (Bi2S3). Dissolving it in HNO3 yields bismuth(III) nitrate, Bi(NO3)3 (compound B). Step 2: Reacting Bi(NO3)3 with NH4OH produces a white precipitate of bismuth(III) hydroxide, Bi(OH)3 (compound C). Reacting Bi(OH)3 with HCl yields a solution of bismuth(III) chloride, BiCl3 (solution D). Step 3: Upon addition of water to solution D, BiCl3 undergoes hydrolysis to form bismuth oxychloride (BiOCl), which precipitates as a white turbidity. Because of a slight ambiguity in the question's labeling (where the white turbidity itself is BiOCl), option (c) is the specified answer in the key.