depression of freezing point of a solvent

definition of freezing

the temperature at which the solid and liquid phases of the substances co exist/ have the same vapour pressure.

explanation

at the freezing point, there are two things in the vessel, the liquid solution and the solid solvent. the solution will freeze at the temperature at which the vapour pressure of both liquid solution and solid solvent will be equal. it means that solution will freeze at lower temperature than pure solvent.

curve ABC

for pure solvent. freezes at T1 corresponding to B where the vapour pressure of the solvent is p not

curve bc

is for solid solvent

curve dec

will meet bc at point e which is the fp of solution at t2 lower than t1 corresponding to vapour pressure p.