Question: Normal boiling point of water is 373 K (at 760 mm). Vapor pressure of water at 298 K is 23 mm. If the enthalpy of evaporation is 40.656 kJ/mol, the boiling point of water at 23 mm pressure will be:

Options:

A) 250 K

B) 294 K

C) 51.6 K

D) 12.5 K

Answer:

Correct Answer: B

Solution:

[b] Applying Clausius—Clapeyron equation, we get logP2P1=ΔHv2.303R[T2T1T1×T2] log76023=406562.303×8.314[373T1373T2] This gives T1 = 294.4 K.