Assuming equal concentrations, rank these aqueous solutions by their freezing point: low to high

Question

NH4Cl, Sn(ClO3)4, Na2SO4, and AlBr3.

Answer 1

delta T = i*Kf*m
f.p. = 0 C - delta T.

So m and Kf are constant; the only variable is i = van't Hoff factor.
i = 2 for NH4Cl
i = 5 for Sn(ClO3)4
i = 3 for Na2SO4
i = 4 for AlBr3.