VIa The vapor pressure, P, of a certain liquid was measured at two temperatures,

Question

VIa The vapor pressure, P, of a certain liquid was measured at two temperatures, T. It you were going to graphically determine the enthalpy of vaporizaton, Hap, for this liquid, what points would you plot? The data is shown in this table Number Number T (K) P (kPa) 275 3.46 775 To avoid rounding errors, use three significant figures in the x values and four significant figures in the y values point 1 5.85 Number Number NOTE: Keep the pressure units in kP.a point 2 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 vap

Explanation / Answer

We need to plot lnK on y axis and 1/T on x axis

P = 3.46

ln P = ln (3.46) = 1.24127

T = 275.0

1/T = 0.00364

point 1 is:

x = 0.00364

y = 1.24127

P = 5.85

ln P = ln (5.85) = 1.76644

T = 775.0

1/T = 0.00129

point 2 is:

x = 0.00129

y = 1.76644

----------------------------------------------------------------------------

rise = (y1-y2) = 1.24127 - 1.76644 = -0.52517

rise = (X1-X2) = 0.00364 - 0.00129 = 0.00235

slope = rise/run

= -0.52517/0.00235

= -223.85502

----------------------------------------------------------------------------

use

slope = - HVap/R

= -223.85502 = -HVap/8.314

HVap = 1861 J/mol

Feel free to comment below if you have any doubts or if this answer do not work. I will edit it if you let me know

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