Depression in freezing point is directly proportional to van't Hoff factor i and i is directly proportional to number of ions furnished by a molecule. Higher the ions furnished, higher is the depression in freezing point and so lower is the freezing point
Compound i
Sucrose = 1 BaCl2=3 KCl=2 FeCl3=4
So, the order of freezing point is FeCl3<KCl<BaCl2<sucrose