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

Options

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

Explanation

`DeltaT_(f)=iK_(f)m`
m is same for all solutions thus, `DeltaT_(f) prop i` (number of ions or molecules) when
`DeltaT_(f)=T_(f)-T_(i)`
`[Co(H_(2)O)_(6)]Cl_(3)implies` 4 iions `(i=4)`
`[Co(H_(2)O)_(5)Cl[Cl.H_(2)Oimplies` 3 ions `(i=3)`
`[Co(H_(2)O)_(4)Cl_(2)]Cl.2H_(2)Oimplies` 2 ions `(i=2)`
`[Co(H_(2)O)_(3)Cl_(3)].3H_(2)Oimplies` No ion (`i=1)`
Freezing point of solution increases, the value of i decreases.
So, highest freezing point will be of `[Co(H_(2)O)_(3)Cl_(3)].3H_(2)O` solution.