JEE Main 2025 Apr 7 Shift 1, Chemistry Q25: Colour, Magnetism And Stability Of Co-ordination Compounds

JEE Main2025Apr 7, Shift 1Chemistry

The number of paramagnetic complex among [FeF $_{6}$ ] $^{3 -}$ , [Fe(CN) $_{6}$ ] $^{3 -}$ , [Mn(CN) $_{6}$ ] $^{3 -}$ , [Co(C $_{2}$ O $_{4}$ ) $_{3}$ ] $^{3 -}$ , [MnCl $_{6}$ ] $^{3 -}$ and [CoF $_{6}$ ] $^{3 -}$ , which involved d $^{2}$ sp $^{3}$ hybridization is ...................

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Solution

For each complex, identify the d-electron count of the metal ion, the field strength of the ligand (strong-field $\Rightarrow$ inner-orbital d $^{2}$ sp $^{3}$ ; weak-field $\Rightarrow$ outer-orbital sp $^{3}$ d $^{2}$ ), and then determine magnetic behaviour.

Complex	Metal config	Ligand field	Hybridisation	Magnetic nature
[FeF $_{6}$ ] $^{3 -}$	Fe $^{3 +}$ , d $^{5}$	weak (F $^{-}$ )	sp $^{3}$ d $^{2}$	paramagnetic
[Fe(CN) $_{6}$ ] $^{3 -}$	Fe $^{3 +}$ , d $^{5}$	strong (CN $^{-}$ )	d $^{2}$ sp $^{3}$	paramagnetic
[Mn(CN) $_{6}$ ] $^{3 -}$	Mn $^{3 +}$ , d $^{4}$	strong (CN $^{-}$ )	d $^{2}$ sp $^{3}$	paramagnetic
[Co(C $_{2}$ O $_{4}$ ) $_{3}$ ] $^{3 -}$	Co $^{3 +}$ , d $^{6}$	strong (ox)	d $^{2}$ sp $^{3}$	diamagnetic
[MnCl $_{6}$ ] $^{3 -}$	Mn $^{3 +}$ , d $^{4}$	weak (Cl $^{-}$ )	sp $^{3}$ d $^{2}$	paramagnetic
[CoF $_{6}$ ] $^{3 -}$	Co $^{3 +}$ , d $^{6}$	weak (F $^{-}$ )	sp $^{3}$ d $^{2}$	paramagnetic

The complexes that satisfy both conditions (paramagnetic AND d $^{2}$ sp $^{3}$ ) are [Fe(CN) $_{6}$ ] $^{3 -}$ and [Mn(CN) $_{6}$ ] $^{3 -}$ .

$∴$ Answer = 2.

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JEE Main 2025 Apr 7 Shift 1, Chemistry Q25: Colour, Magnetism And Stability Of Co-ordination Compounds

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