Discussion

Answer: A

The incorrect statement is (A): the two compounds do not show equal quadrupole splitting.

Quadrupole splitting measures the electric field gradient at the iron nucleus, and in both compounds the I = 3/2 excited state splits into two levels, so each gives a doublet. FeCl₃.6H₂O contains high-spin Fe(III), d⁵, whose half-filled t_2g³e_g² shell is spherical, so the valence electrons add no field gradient and only the lattice (ligand) contribution acts: the splitting is small. FeCl₂.4H₂O contains high-spin Fe(II), d⁶, whose extra electron sits in a non-spherical d orbital and adds a large valence contribution, so its splitting is much larger. The splittings are therefore unequal, which makes (B) true, and (D) states exactly this valence versus lattice difference.

Statement (C) is true in substance: both salts are high-spin, and the pair is one Fe(III) and one Fe(II) complex. As printed, 'respectively' pairs Fe(II) with the first formula, FeCl₃.6H₂O, which is the wrong way round; the question evidently means only the pair of oxidation states, so (A), false on any reading, is the answer. The splitting values themselves are not quoted here; the argument rests on the d⁵ versus d⁶ electronic structure.