Answer:
Van't Hoff factor is 1.72 ≅ 2
Step-by-step explanation:
Let's apply the colligative property of boiling point elevation:
ΔT = Kb . m . i
ΔT = Boiling T° of solution - T° boiling of pure solvent
103.45 °C - 100°C = 0.512 °C/m . 3.90 m . i
3.45 °C / 0.512 m/°C . 3.90 m = i
1.72 = i ≅ 2