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Crystal Field Split in Octahedral Complexes

[FeCN6]4- and...

Question

$[F e (C N)_{6}]^{4 -}$ and $[F e (H_{2} O)_{6}]^{2 +}$ show different colours in dilute solutions because?

C N^{-}

is a strong filed ligand and

H_{2} O

is a weak filed ligand hence magnitude of CFSE is different

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both

C N^{-}

and

H_{2} O

absorb same wavelength of energy

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complexes of weak filed ligands are generally colourless

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the sizes of

C N^{-}

and

H_{2} O

are different hence their colours are also different.

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Solution

The correct option is A $C N^{-}$ is a strong filed ligand and $H_{2} O$ is a weak filed ligand hence magnitude of CFSE is different
$F e (C N)_{6}]^{4 -} \Rightarrow F e^{2 +} \Rightarrow [A r] 3 d^{6}$
Where $F e^{2 +} = C ¯ N \to$ Strong field ligand.
So, the energy gap is high.
$F e (H_{2} O)_{6}]^{2 +} \Rightarrow F e^{2 +} \Rightarrow [A r] 3 d^{6}$
Where $H_{2} O =$ Weak field ligand.
Energy gap is low.

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Similar questions

Q. Classify weak and strong ligands out of :
(a)

O H^{-}

(b)

F^{-}

(c)

I^{-}

(d)

N H_{3}

(e)

C H_{3} C O O^{-}

(f)

e n

(g)

C N^{-}

(h)

C l^{-}

(i)

H_{2} O

F^{-}, I^{-}, C l^{-}

and

H_{2} O

are weak ligands, other are strong lignads.
If true enter 1, else enter 0.

Q. Assertion :

[F e (H_{2} O)_{6}]^{3 +}

is strongly paramagnetic whereas

[F e (C N)_{6}]^{3 -}

is weakly paramagnetic. Reason:

H_{2} O

is a week field ligand and

C N^{-}

is a strong field ligand.

Q. Transition metal complexes containing,

C N^{-}

ligands are often yellow in colour, whereas those containing

H_{2} O

ligands are often green or blue. This is because

C N^{-}

is a strong ligand. Absorption takes place near

U V

(blue) and so, they appear yellow.
If true enter 1, else enter 0.

[F e (C N)_{6}]^{4 -}

and

[F e (H_{2} O)_{6}]^{2 +}

are of different colours in dilute solutions. Why?

Q. Assertion :

[F e (H_{2} O)_{6}]^{2 +}

s p^{3} d^{2}

hybridised and paramagnetic complex ion. Reason:

[F e (H_{2} O)_{6}]^{2 +}

has four unpaired electrons as

H_{2} O

is a weak field ligand.

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[Fe(CN)6]4− and [Fe(H2O)6]2+ show different colours in dilute solutions because?

The correct option is A CN− is a strong filed ligand and H2O is a weak filed ligand hence magnitude of CFSE is differentFe(CN)6]4−⇒Fe2+⇒[Ar]3d6Where Fe2+=C¯N→ Strong field ligand.So, the energy gap is high.Fe(H2O)6]2+⇒Fe2+⇒[Ar]3d6Where H2O= Weak field ligand.Energy gap is low.

$[F e (C N)_{6}]^{4 -}$ and $[F e (H_{2} O)_{6}]^{2 +}$ show different colours in dilute solutions because?