If the freezing point of a 0.01 molal aqueous solution of a cobalt(III) chloride-ammonia complex (which behaves as a strong electrolyte) is $- {0.0558}^{\circ} C,$ the number of chloride(s) in the coordination sphere of the complex is:
$[K_{f}$ of water = 1.86 $K k g m o l^{- 1}$ ]

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Solution

The Vant Hoff factor is $i = \frac{Δ T_{f}}{k_{f} \times m} = \frac{0.0558}{1.86 \times 0.01} = 3$

Thus, the complex dissociates to give 3 ions.

Hence, the complex is $[C o (N H_{3})_{5} C l] C l_{2}$ with 1 chloride ion in the coordination sphere.

$[C o (N H_{3})_{5} C l] C l_{2} \to [C o (N H_{3})_{5} C l]^{2 +} + 2 C l^{-}$

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If the freezing point of a 0.01 molal aqueous solution of a cobalt chloride ammonia complex ( which behaves as a strong electrolyte ) is 0.0558 degree Celsius, the number of chloride in the coordination sphere of the complex is ? (kf of water = 1.86k kg/mole