A pale green solution gives a deep blue precipitate with K3[Fe(CN)6] but no red coloration with KSCN before oxidation. The ion present is

JEE Main levelSingle correct optionDifficulty 2 of 3qc134

A pale green solution gives a deep blue precipitate with $K X_{3} [Fe (CN) X_{6}]$ but no red coloration with $KSCN$ before oxidation. The ion present is

Fe X^{2 +}

gives Turnbull's blue,

Fe X_{3} [Fe (CN) X_{6}] X_{2}

, with ferricyanide, and

Fe X^{2 +}

does not give the blood-red colour with thiocyanate.

Fe X^{3 +}

would give red with

KSCN

and only a brown-green colour with ferricyanide.

Co X^{2 +}

and

Cu X^{2 +}

do not give a deep blue precipitate here.