Vant hoff

Hej :)

Jeg er gået i stå med den sidste opgave i kemi spm. ser således ud:

Consider an aqueous 1.00 mol kg-1 solution of Na3PO4, a compound with useful detergent properties. Calculate the boiling point of the solution assuming that:
(a) it does not ionise at all in solution

Svar : 

ΔT_(opl.)= ΔT_f + ?T_vand=1,86 K+373,15 K
 ΔT_(opl.)=375,01 K

(b) the van't Hoff factor for Na3PO4 reflects 100 % dissociation into its ions.

Svar

ΔT_(opl.)= ΔT_f + ?T_vand=7,44 K+373,15 K
 ΔT_(opl.)=380,59 K

The 1.00 mol kg-1 solution boils at 100.83 oC at 1.0 x 105 Pa.                               

(c) Calculate the van't Hoff factor for the solute in this solution.

Her er jeg lost.Skal jeg bruge formelen for osmotisk tryk?ALtså

π=C*R*T og isoler C som vant Hoff factor?