Question

What is the freezing point of a 1.40 m aqueous solution of a nonvolatile un-ionized solute? (the freezing point depression constant for water is 1.86°c kg solvent/mol solute.)?

Answer 1

Depression is freezing point is a colligative property. It is mathematically expressed as ΔTf = Kf X m

where Kf = freezing point depression constant = 1.86°c kg /mol (for water)
m = molality of solution = 1.40 m

∴ ΔTf = Kf X m  = 1.86 X 1.40 = 2.604 oC

Now, for water freezing point = 0 oC

∴Freezing point of solution = -2.604 oC