Question

Alculate the freezing point of solution when 1.9 g of mgcl2 (m = 95 g mol1) was dissolved in 50 g of water, assuming mgcl2 undergoes complete ionization. (kf for water = 1.86 k kg mol1)

Answer 1

DelTf = i Kf molality

molality =1.9/95 x1000/50

molality = 0.02 x20 =0.4

DelTf =3x1.86x 0.4 =2.23. ( i =3 mg2+ 2cl-)

Freezing point of solution = -2.23 Celsius