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
Choose the most appropriate answer from the options given below:
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
Choose the most appropriate answer from the options given below:
- A.A and D only
- B.A and C only
- C.A only
- D.B and C only
Show answer and solution
Correct option: A
Solution
In depression of freezing point, adding a non-volatile solute lowers the vapour pressure of the solution compared to the pure solvent (Raoult's law), so statement A is correct. At the freezing point of the solution, it is the solvent molecules that begin to solidify (form pure solid solvent crystals), not the solute — this is exactly why the freezing point is depressed (equilibrium between solid solvent and solution). So statement D is also correct, making A and D the right combination.
[JEE Main 2023 · 24 Jan · Shift 1 · Paper-1(B.E./B. Tech.)]