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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