GAses LOUIDS AND SOLOS Calculating vapor pressure from boili

GAses, LOUIDS AND SOLOS Calculating vapor pressure from boiling point and enthalpy of v... Ab kJ mol The enthalpy of vaporization of Substance is 17.0 and its normal boiling point is 72·°C. Calculate the vapor pressure of Xat-173, C Round your answer to 2 significant digits. 0atem

Solution

According to Clausius-Clayperon equation,
ln (P\'/P) = (-L/R) x [(1/T\') - (1/T)]
Where
P\' = vapour pressure at T\'
P = vapour pressure at T
R = gas constant = 8.314 J/(mol-K)
T\' = initial temperature
T = final temperature
L = heat of vaporization of this substance = ?
Plug the values we get
ln (P\'/P) = (-L/R) x [(1/T\') - (1/T)]

Given P= 1 atm

T= -72 oC= -72+273= 201 K

P\'= ?

T\'= -173 oC= -173+273= 100K

L= 17.0 kJ/ mol= 17.0*10^3 J/ mol

Plug the values we get P\'= 3.45*10^-5 atm