JEE Main levelSingle correct optionDifficulty 2 of 3qa137
Match the anion (List I) with the observation on warming its salt with concentrated HX2SOX4 (List II).
List I: P ClX−, Q IX−, R CX2OX4X2−, S NOX3X− (with copper turnings added).
List II: 1 violet vapours, 2 brown fumes and a blue solution, 3 colourless gas giving white fumes with ammonia, 4 gas mixture whose residue after COX2 removal burns with a blue flame.
AP-3, Q-1, R-4, S-2
BP-1, Q-3, R-4, S-2
CP-3, Q-1, R-2, S-4
DP-3, Q-4, R-1, S-2
Answer: A
Chloride gives HCl (white fumes with NHX3), iodide gives violet IX2 vapour, oxalate gives CO and COX2 (the CO burns blue), and nitrate with copper gives brown NOX2 and blue CuX2+. The matching is P-3, Q-1, R-4, S-2.