Question

Colourless complex ion in the following is

(a) [Cu(NH,)1* (b) [Zn(NHs)41*

(c) [Fe(H20)1* (d) [Fe(CN)

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Answer 1

Answer:

answer is option c .....

Answer 2

(b) $[Zn(NH_3)_4]^{2+}$ is colourless.

• Electronic configuration of $Zn$ is $3d^{10}4s^{2}$ within it's valence shell.

Since $NH_3$ is neutral ligand, $Zn$ exists as +2 oxidation state.

So, four ligands are there ,and d orbital is completely filled then it will undergoes $sp^{3}$ hybridization and tetrahedral geometry. As, it does not have any unpaired electron, $[Zn(NH_3)_4]^{2+}$ does not have any colour.

• Other ions have unpaired electrons in their valance shell, so they show colours.

(a) $[Cu(NH_3)_4]^{2+}$ shows dark blue colour.

(c) $[Fe(H_2O)_6]^{3+}$ has yellow colour.

(d) $[Fe(CN)_6]^{3-}$ is bright red.

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