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: When NaOH is added to the mixture containing Al3+, Zn2+, and Cu2+, all of them initially form hydroxide precipitates. Step 2: Since Al(OH)3 and Zn(OH)2 are amphoteric, they dissolve in excess NaOH to form soluble aluminate ([Al(OH)4]-) and zincate ([Zn(OH)4]2-) complexes. Step 3: In contrast, Cu(OH)2 is a basic hydroxide and remains insoluble as a characteristic blue precipitate, allowing both the identification and separation of Cu2+ in one step, matching option (c).