Q. Consider the given plots of vapour pressure (VP) vs temperature (T/K). Which amongst the following options is correct graphical representation showing $\Delta T_f$, depression in the freezing point of a solvent in a solution?
A) [image:2025J24S1_Q69_opt_a.png]
B) [image:2025J24S1_Q69_opt_b.png]
C) [image:2025J24S1_Q69_opt_c.png]
D) [image:2025J24S1_Q69_opt_d.png]
Explanation
[Solution by Dr. Abubacker] The vapour pressure curve of the solution lies below that of the pure liquid solvent. The solid (frozen) solvent curve meets the solution curve at the new freezing point $T_f$, which is lower than $T_f^\circ$ (where the frozen solvent curve meets the pure liquid solvent curve). Option (1) shows this arrangement, with $\Delta T_f=T_f^\circ-T_f$. Answer (1).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.