In the depression of freezing point experiment
A. Vapour pressure of the solution is less than that of pure solvent
B. Vapour pressure of the solution is more than that of pure solvent
C. Only solute molecules solidify at the freezing point
D. Only solvent molecules solidify at the freezing point
A. Vapour pressure of the solution is less than that of pure solvent
B. Vapour pressure of the solution is more than that of pure solvent
C. Only solute molecules solidify at the freezing point
D. Only solvent molecules solidify at the freezing point
- (A)A and D only✓ Correct
- (B)B and C only
- (C)A and C only
- (D)A only
Answer: (A)
Solution
Adding a non-volatile solute lowers the vapour pressure of the solution below that of the pure solvent, so the solution's vapour pressure is less, not more. When the solution is cooled to its freezing point, the solvent alone crystallises while the solute stays dissolved. The correct statements are that the vapour pressure of the solution is lower than that of the pure solvent and that only solvent molecules solidify at the freezing point.
JEE Main · 2023 · 24 Jan 2023 · Shift 1 · Single correct option