The vapor pressure of ethanol is 400 mmHg at 63.5°C. Its molar heat of vaporization is 39.3 kJ/mol. What is vapor pressure of ethanol, in mmHg, at 34.9°C?
A)1,510 mmHg
B)100 mmHg
C)200 mmHg
D)0.0099 mmHg
E)4.61 mmHg

Question

Quizplus · Accepted Answer

The Clausius-Clapeyron equation relates vapor pressure and temperature: ln(P2/P1) = -ΔHvap/R * (1/T2 - 1/T1). Using this with P1 = 400 mmHg, T1 = 336.65 K, T2 = 308.05 K, ΔHvap = 39,300 J/mol, and R = 8.314 J/mol·K, we find P2 ≈ 100 mmHg.

The Vapor Pressure of Ethanol Is 400 MmHg at 63