Question

which of the following aqueous liquids will have the lowestfreezing point?

0.5 m Ca(NO3)2
pure water
0.5 m Li3PO4
0.5 m C12H22O11(sucrose)
0.5 m NiSO4

Answer 1

     Depression in freezing point dependson the colligative property i.e it depends on the number of ions ofthe salt.

      So for the given salts

         0.5 mLi₃PO₄ gives four ions ondissociation ( 3 Li⁺ + PO₄^-3 ) = i

             Δ T_f = i Kf xmolality of the solution

        

Answer 2

Li3PO4 --> 3 Li+ + PO4^3- 1 0 0 1- a 3a a total no of moles after dissociation, i= 1+3a which is highest for Li3PO4 now delta Tf= i* Kf*m m and Kf for same solvent is same delta Tf is greatest for high value of i which is Li3PO4