CBSE Class 12 · Coordination CompoundsShort Answer

(a) Write the formula of the coordination compound iron(III) hexacyanidoferrate(II).
(b) What type of isomerism is exhibited by the complex [Co(NH

_{3}

)

_{5}

Cl]SO

_{4}

?
(c) Write the hybridisation and the number of unpaired electrons in the complex [CoF

_{6}

]

^{3 -}

. (Atomic number of Co = 27)

Answer: (a) Fe₄[Fe(CN)₆]₃ (Prussian blue). (b) Ionisation isomerism (with [Co(NH₃)₅(SO₄)]Cl). (c) sp³d²; 4 unpaired electrons.

Solution

(a) Fe

^{3 +}

cations with [Fe(CN)

_{6}

]

^{4 -}

anions — balance 4 × (+3) = 3 × (−4):

F e_{4} [Fe (CN)_{6}]_{3} (Prussian blue)

(b) \textbf{Ionisation isomerism} — the SO

_{4}^{2 -}

counter-ion can exchange with the coordinated Cl

^{-}

: [Co(NH

_{3}

)

_{5}

Cl]SO

_{4}

and [Co(NH

_{3}

)

_{5}

(SO

_{4}

)]Cl give different ions in solution.
(c) Co

^{3 +}

= 3d

^{6}

with weak-field F

^{-}

: no pairing — hybridisation \textbf{sp

^{3}

^{2}

} (outer-orbital), \textbf{4 unpaired electrons}.

CBSE Class 12 Board · Subjective