Question

A 4.6-L sealed bottle containing 0.39 g of liquid ethanol, C2H6O, is placed in a refrigerator and reaches equilibrium with its vapor at −11°C. The vapor pressure of ethanol is 10. torr at −2.3°C and 40. torr at 19°C.(c) How much liquid ethanol would be present at 0.0°C?

Answer 1

First we have to calculate the enthalpy of vaporization

Vapor pressure at -2.3 ^oC = P₁ =10 torr

Vapor pressure at 19 ^oC = P₂ = 40 torr

Initial temperature = T₁ = -2.3 ^oC = 270.85 K

Final temperature = T₂ = 19 ^oC = 292.15 K

R = 8.314 J/K.mol

Using Clausius-Clapeyron equation