Discussion Forum

1)

 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:

Option A

Explanation:

 $+\triangle T_{f}= iK_{f}m$

  $\triangle T_{f}=0-(-0.0588^{0}C)=0.0558^{0}C$

  $\Rightarrow$       i(vant Hoff's factor )=  $\frac{0.0558}{1.86\times 0.01}=3$

 This indicates that complex upon ionisation  produces  three ions as:

  $[Co(NH_{3})_{5}Cl]Cl_{2}\rightarrow\left[ Co\left(NH_{3}\right)_{5}Cl\right]^{2+}(aq)+2Cl^{-}(aq)$

 Thus, only  me Cl is inside the coordination sphere.