A colourless inorganic compound (A) imparts a green colour to the flame. Its solution gives a white — Qualitative and Quantitative Analysis Chemistry Question
Question
A colourless inorganic compound (A) imparts a green colour to the flame. Its solution gives a white ppt. (B) with H2SO4. When heated with K2Cr2O7 and conc. H2SO4, a brown red vapour/gas (C) is formed. The gas/vapour when passed through aqueous NaOH solution, it turns into a yellow solution (D) which forms yellow precipitate (E) with CH3COOH and (CH3COO)2Pb. With reference to above information, answer the following questions.
💡 Solution & Explanation
Step 1: The reaction of bismuth(III) ions with iodide ions (I-) initially forms a dark brown/black precipitate of bismuth(III) iodide (BiI3). Step 2: The black BiI3 precipitate reacts with excess iodide ions to form a highly stable, soluble tetraiodobismuthate(III) complex anion: BiI3 + I- -> [BiI4]-. Step 3: The [BiI4]- complex solution exhibits a characteristic orange/yellow-orange color. This confirms the presence of Bi3+, matching option (b).