he vapor pressure, P, of a certain liquid was measured at two temperatures, T. T
ID: 832335 • Letter: H
Question
he vapor pressure, P, of a certain liquid was measured at two temperatures, T.
The data is shown right below:
T(K) P(kPa)
255 371
775 6,56
If you were going to graphically determine the enthalpy of vaporization, deltaHvap, for this liquid, what popints would you plot? (To avoid rounding errors use 3 significant figures in the x values and 4 significant figures in the y values)
x y
Point 1 ____ ____
Point 2 ____ ____
Determine the rise, run, and slope of the line formed by these points.
Rise Run Slope
_____ _____ ______
What is the enthalpy of vaporization of this liquid?
deltaHvap =_________J/mol
Explanation / Answer
-----
Clausius-Clapeyron Equation:
ln (p1/p2) = (delta Hvap / R)(1/T2 - 1/T1)
you just plug in the values that you have for p1, p2, T1, and T2 where R= 8.3145 J mol-1 K-1
so: ln (371/656) = (delta H /8.314)(1/775 - 1/255)
-0.57(8.314) = delta H(0.00129-0.00392)
-4.738 = delta H X -0.00236
delta H =2007.63 J/mol = 2.007 KJ/mol.
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