Question #73593

1 Answer
P dilip_k
Feb 2, 2017

The Clausius-Clapeyron equation relates the vapor pressures of a liquid at two temperatures along with the enthalpy of vaporisation of liquid as follows.

color(blue)(ln(P_2/P_1)=(DeltaH_"vap")/R(1/T_1-1/T_2))

where

DeltaH_"vap"->"Enthalpy of vaporisation"

P_1->"Vapor preessure at "T_1K

P_2->"Vapor preessure at "T_2K

R->"Universal gas constant"

In our problem for ether we have been given

T_1=(-22.8+273)K=250.2K

T_2=(25+273)K=298K

P_1=57.0mm

P_2=534mm

R=8.314JK^-1mol^-1

Inserting these in the equation

color(green)(ln(P_2/P_1)=(DeltaH_"vap")/R(1/T_1-1/T_2))

=>color(blue)(ln(534/57)=(DeltaH_"vap")/8.314(1/250.2-1/298))

=>DeltaH_"vap"=(298xx250.2xx8.314)/47.8ln(534/57)Jmol^-1

~~29.0kJ

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