For 1 molal aqueous solution of the following compounds, which one will show the highest freezing point ?

Options

A. `[Co(H_(2)O)_(5)Cl]Cl_(2).H_(2)O`
B. `[Co(H_(2)O)_(4)Cl_(2)]Cl.2H_(2)O`
C. `[Co(H_(2)O)_(3)Cl_(3)].3H_(2)O`
D. `[Co(H_(2)O)_(6)]Cl_(3)`

Answer

C

Explanation

The complex having minimum value of vant Hoff's factor will give minimum concentration and highest freezing point.
(a) `[Co(H_(2)O)_(5)Cl]Cl_(2).H_(2)O rarr [Co(H_(2)O)_(5)Cl]^(+2)+2Cl^(-) (i=3)`
(b) `[Co(H_(2)O)_(4)Cl_(2)]Cl.2H_(2) rarr [Co(H_(2)O)_(4)Cl_(2)]^(+)+Cl^(-) (i=2)`
(c ) `[Co(H_(2)O)_(3)Cl_(3)]3H_(2)O rarr` No dissociation (i=1)
(d) `[Co(H_(2)O)_(6)]Cl_(3)rarr[Co(H_(2)O)_(6)]^(+3)+3Cl^(-) (i=4)`