JEE Advanced · 2015 · 24 May 2015 · Paper 1 · Solutions

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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 °C, the number of chloride(s) in the coordination sphere of the complex is

[K_{f}

of water

= 1.86 K kg mol^{- 1}]

Answer: 1

Solution

Using

Δ T_{f} = K_{f} \times i \times m

0.0558 = 1.86 \times i \times 0.01

i = 3

Since the complex is a strong electrolyte with i=3, it dissociates into 3 particles.

The complex must be

[Co (NH_{3})_{5} Cl] Cl_{2}

, which dissociates as:

[Co (NH_{3})_{5} Cl]^{2 +} + 2 Cl^{-}

(3 particles)

Number of chlorides in the coordination sphere = 1.

JEE Advanced · 2015 · 24 May 2015 · Paper 1 · Integer answer

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