Solid KCl, when heated with solid K2Cr2O7 and concentrated H2SO4, gives red vapours (a) that turn NaOH solution yellow (b). The yellow solution, when acidified with acetic acid and treated with lead a

Question

Solid KCl, when heated with solid K2Cr2O7 and concentrated H2SO4, gives red vapours (a) that turn NaOH solution yellow (b). The yellow solution, when acidified with acetic acid and treated with lead acetate, gives a yellow precipitate (c). Which of the following is true with respect to a, b and c?

Prashant Kotian · Accepted Answer

Correct answer: D. 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).

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