The vapor pressure, P, of a certain li was measured at two temperatures, If you

Question

The vapor pressure, P, of a certain li was measured at two temperatures, If you were going to graphically determine the enthalpy of vaporizaton, dHvp, for this liquid, what points would you plot? The data is shown in this table Number Number T(K) P (kPa) 225 3.79 575 To avoid rounding errors, use three significant figures in the x values and four significant figures in the y values. point 1: 8.87 NOTE: Keep the pressure units in kPa. 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

Explanation / Answer

We need to plot lnK on y axis and 1/T on x axis
P = 3.79
ln P = ln (3.79) = 1.33237
T = 225.0
1/T = 0.00444


point 1 is:
x = 0.00444
y = 1.33237


P = 8.87
ln P = ln (8.87) = 2.18267
T = 575.0
1/T = 0.00174


point 2 is:
x = 0.00174
y = 2.18267


----------------------------------------------------------------------------
rise = (y1-y2) = 1.33237 - 2.18267 = -0.85031
rise = (X1-X2) = 0.00444 - 0.00174 = 0.00271
slope = rise/run
= -0.85031/0.00271
= -314.31057
----------------------------------------------------------------------------
use
slope = - delta H/R
= -314.31057 = -delta H/8.314
delta H = 2613.178 J/mol
Answer: 2613.178 J/mol

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