Question

In an experiment, 16.8 g of k2so4 was dissolved in 1.00 kg of water to make a solution. the freezing point of the solution was measured to be −0.405°c . calculate the van't hoff factor (i) for this solution. the freezing point of pure water is 0°c (exactly) at 1 atm pressure and the molal freezing-point depression constant for water is 1.86°c/m.

Answer 1

Answer is: Van't Hoff factor (i) for this solution is 2,26.
Change in freezing point from pure solvent to solution: ΔT =i · Kf · m.
Kf - molal freezing-point depression constant for water is 1,86°C/m.
m -  molality, moles of solute per kilogram of solvent.
n(K₂SO₄) = 16,8 g ÷ 174,25 g/mol
n(K₂SO₄) = 0,096 mol.
m(K₂SO₄) = 0,096 mol/kg.
ΔT = 0,405°C.
i = 0,405 ÷ (1,86 · 0,096)
i = 2,26.