Solutions Question 376
Question: 0.5 m solution of a complex of iron and cyanide ions has the depression of f.pt. to be 3.72 K ( $ K_{f} $ For water $ =1.86Kmola{l^{-1}} $ ). The formula of the complex is:
Options:
A) $ K_4[Fe{{(CN)}_6}] $
B) $ K_2[Fe{{(CN)}_4}] $
C) $ K_3[Fe{{(CN)}_6}] $
D) $ Fe{{( CN )}_4} $
Show Answer
Answer:
Correct Answer: C
Solution:
$ \Delta T_{f}(normal)=K_{f}m=1.86\times 0.5=0.93{}^\circ $ Assuming 100% ionization, i = n = No. of ions per molecule $ =\frac{Observed,\Delta T_{f}}{Normal,\Delta T_{f}}=\frac{3.72}{0.93}=4 $
$ K_3[Fe{{(CN)}_6}]\xrightarrow{{}}3{K^{+}}+{{[Fe{{(CN)}_6}]}^{3-}} $ No. of ions = 4
