Question

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 – 0.05580C, the number of chloride(s) in the coordination sphere of the
complex is
[K???? of water = 1.86 K kg mol⁻¹]

Answer 1

Given:

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 – 0.05580C

To find:

The number of chloride(s) in the coordination sphere of the complex is

Solution:

From given, we have,

a 0.01 molal aqueous solution of a cobalt (III) chloride-ammonia complex(which behaves as a strong electrolyte) is – 0.05580C

Kf of water = 1.86 K kg mol⁻¹

Δ Tf = 0.0558 °C

m = 0.01

For a strong electrolyte i = n

where, n = number of ions

we use the formula,

Δ Tf = i Kf m

⇒ i = Δ Tf / Kf × m

⇒ i = 0.0558/(1.86 × 0.01)

∴ i = 3

⇒ i = n = 3

[Co(NH₃)₅Cl]Cl₂ with the number of chlorides 3 is the correct answer