Analytical ChemistryHard

Question

An aqueous solution of salt containing an acidic radical X- reacts with sodium hypochlorite in neutral medium. The gas evolved produces blue black colour spot on the starch paper. The anion X- is :

Options

A.CH3COO-
B.Br-
C.I-
D.NO2-

Solution

OCl- + 3I- + H2O →  I3- + 2OH- + Cl-.
I3- + starch →  blue -black spot on starch paper due to the formation of iodine-starch adsorption complex.

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