Map d The vapor pressure P of a certain liquid was measured

Map d The vapor pressure, P, of a certain liquid was measured at two temperatures, T If you were going to graphically determine the enthalpy of vaporizaton, AHvap, for this liquid, what points would you plot? The data is shown in this table Number To avoid rounding errors, use three significant figures in the x values and fou significant figures in the y values point 1 325 3.09 875 5.91 NOTE: Keep the pressure units in kPa. point ! ] Determine the rise, run, and slope of the line formed by these points rise run slope Number Number Number What is the enthalpy of vaporization of this liquid? Number J/mol ap Next Exit Previous Give Up & View Solution 9 Check Answer

Solution

Classius- Clayperon Equation

ln(P2/P1)= (deltaHvap/R)*(1/T1-1/T2)

P2= pressure corresponding to temperature T2 in K

P1= pressrue corresponding to temperature T1 in K

deltaH vap= latent heat of vaporization and R = gas constant= 8.314 J/mole.K

so the plot of lnP vs 1/T gives straight line whose slope is -deltaH/R

given P1=3.09 Kpa and T1= 325K and P2= 5.91 Kpa and T2 =875 K

x- axis is 1/T and y-axis is Pressure in Kpa

1/T1= 1/325 =0.003077 and lnP1= ln(3.09)=1.128

1/T2= 1/875= 0.001143 and lnP2= ln(5.91)= 1.78

run = 1/T1-1/T2= 0.003077-0.001143= 0.001934 and rise = 1.78-1.128= 0.652

slope =-0.652/0.001934=-337.12

-deltaH/R= -337.12

deltaH= 337.12*8.314 J/mole =2803 J/mole