The blue precipitate formed by the action of K4[Fe(CN)6] on Fe3+ and by that of K3[Fe(CN)6] on Fe2+ — Qualitative and Quantitative Analysis Chemistry Question

💡 Solution & Explanation

Step 1: Bromide and iodide ions can be selectively oxidized to free bromine (Br2) and iodine (I2) by a stronger oxidizing halogen like chlorine. Step 2: Adding chlorine water in the presence of an organic solvent (such as CHCl3 or CCl4) oxidizes Br- and I- to Br2 (orange/brown in organic layer) and I2 (violet/purple in organic layer) respectively. Step 3: This 'layer test' using chlorine water allows clear identification based on the color of the organic phase, corresponding to option (a).