Question

Rank the following from lowest to highest freezing point (using the vant hoff factor) HNO3-, Ba(NO3)2, sucrose, and NH3(which is a weak electrolyte not a non electrolyte, says so in my textbook).

Answer 1

Freezing point is related to how many ions the compound will produce in solution, and the molality of the solution (It is not provided here), using Van't Hoff relationship for freezing point depression

Tf = Kf*m*i

let us take wach 1 mole

HNO3- = Kf x 1 x 2

Ba(NO3)2 = Kf x 1 x 3

sucrose =  Kf x 1 x 1

NH3 = Kf x 1 x 1

So, since a larger Tf means a greater depression (lower freezing point)

Lowest ====> Ba(NO3)2 < HNO3- < NH3 (Weak electrolyte) < Sucrose <==== Highest