Sebanyak 6 gram urea (Mr=60) dilarutkan dalam 250 gram air suhu larutan saat mulai membeku (kf air=1,86 c/m)

m
= (gr/mr) x (1000/gr pelarut)
= (6/60) x (1000/250)
= 0,1 x 4
= 0,4 mol

ΔTf
= Kf x m
= 1,86 x 0,4
= 0,744°C

ΔTf = Tf air - Tf larutan
0,744 = 0 - Tf larutan
Tf Larutan = - 0,744°C