The reaction of K 3 [Fe(CN) 6 ] with freshly prepared FeSO 4 solution produces a dark…

The reaction of K₃[Fe(CN)₆] with freshly prepared FeSO₄ solution produces a dark blue precipitate called Turnbull’s blue. Reaction of K₄ [Fe(CN)₆] with the FeSO₄ solution in complete absence of air produces a white precipitate X, which turns blue in air. Mixing the FeSO₄ solution with NaNO₃, followed by a slow addition of concentrated H₂SO₄ through the side of the test tube produces a brown ring.
In the scheme given below, X and Y, respectively, are (2023)
Metal halide \(\xrightarrow{\text { aq. } \mathrm{NaOH}}\) White precipitate (P) + Filtrate (Q)
P \(\xrightarrow[\text { heat }]{\text { aq. } \mathrm{H}_{2} \mathrm{SO}_{4} \mathrm{PbO}_{2} \text { (excess) }}\) X (a coloured species in solution)
Q \(\xrightarrow[\text { warm }]{\mathrm{MnO}(\mathrm{OH})_{2} \text { Conc. } \mathrm{H}_{2} \mathrm{SO}_{4}}\) Y (gives blue-coloration with KI-starch paper)