A complex is represented as CoCl₃. xH₂O. Its 0.1 m solution in aqueous medium shows $∆$ Tf = 0.558 K.. K_f for water is 1.86 kg mol^-1 K and assuming 100% ionisation of the complex having coordination number 6. The formula of the complex is

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$[Co {(H_{2} O)}_{6}] {Cl}_{3}$

$[Co {(H_{2} O)}_{4} {Cl}_{2}] Cl$

$[Co {(H_{2} O)}_{4} Cl] {Cl}_{2}$

$[Co {(H_{2} O)}_{5} Cl] {Cl}_{2}$

answer is D.

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Detailed Solution

$\begin{array}{l} {ΔT}_{f} = i \times K_{f} \times m \\ 0 .558 = i \times 1 .86 \times 0 .1 \Rightarrow i = 3 \end{array}$
So, the total no of ions produce by complex per mole should be 3,and also should have coordination number as 6
$[Co {(H_{2} O)}_{5} Cl] {Cl}_{2} \to [Co {(H_{2} O)}_{5} {Cl}^{2 +} + 2 {Cl}^{-}$