Question

A complex is represented as $CoCl_{3}.xH_{2}O$ . Its $\text{0} \text{.1} \, \text{m}$ solution in aqueous medium shows $\Delta T_{f}= \, 0.558 \, K$ . $K_{f}$ for water is $1.86 \, kg \, m o l^{- 1} \, K$ and assuming $\text{100\%}$ ionisation of the complex having coordination number $\text{6}$ . The formula of the complex is

• A. $\left[C o \left(H_{2} O\right)_{4} C l\right]Cl_{2}$
• B. $\left[C o \left(H_{2} O\right)_{4} C l_{2}\right]Cl$
• C. $\left[C o \left(H_{2} O\right)_{6}\right]Cl_{3}$
• D. $\left[C o \left(H_{2} O\right)_{5} C l\right]Cl_{2}$

Answer 1

Answer: (D)

$\Delta T_{f}=i\times K_{f}\times m$

$0.558=i\times 1.86\times 0.1\Rightarrow i=3$

So, the total no of ions produce by complex per mole should be $3$

$\left[C o \left(H_{2} O\right)_{5} C l\right]Cl_{2} \rightarrow \left(\left[C o \left(H_{2} O\right)_{5} C l\right]\right)^{2 +}+2Cl^{-}$