Solutions of the same molality of a non-volatile non-electrolyte are prepared in four different solvents. In which solvent will the depression in freezing point be the largest?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Carbon tetrachloride
For a dilute solution, ΔTf = Kf m. When the molality m is the same, the depression is largest in the solvent with the largest Kf. Kf depends on the nature of the solvent:
Water: 1.86 K kg mol−1
Benzene: 5.12 K kg mol−1
Cyclohexane: 20.00 K kg mol−1
Carbon tetrachloride: 31.8 K kg mol−1, the largest of the four.
NCERT (2026-27 edition):
1.6.3 Depression of Freezing Point – “The proportionality constant, Kf, which depends on the nature of the solvent is known as Freezing Point Depression Constant or Molal Depression Constant or Cryoscopic Constant. The unit of Kf is K kg mol-1. Values of Kf for some common solvents are listed in Table 1.3.”
Table 1.3: Molal Boiling Point Elevation and Freezing Point Depression Constants for Some Solvents
