Chem 162 Experiment #3: Intermolecular Forces
Part II: Vapor Pressure and Enthalpy of Vaporization
PURPOSE (4 pts)
The purpose is to measure the enthalpies of vaporazation of pentane, diethyl ether, butanone, and 2-butanol. For
each of these molecules, a portion of the enthalpy of vaporization is due to dispersion forces (all molecules have
dispersion forces) and the other to a polar component. In the boxes provided below, draw the structural formula for
each molecule (should be drawn by hand or using a drawing tool - not copy/pasted from a website).
Part I: 26 points (report worksheet completed and handed in before leaving lab)
Part II: 24 points (take-home report)
Lab notebook pages: 10 pts
Total: 60 pts
By signing below, you certify that you have not falsified data, that you have not plagiarized any part of this lab report, and that all
calculations and responses other than the reporting of raw data are your own independent work. Failure to sign this declaration
will result in 5 points being deducted from your report score.
Signature:
Draw the structural formula for pentane: Draw the structural formula for diethyl ether:
Draw the structural formula for butanone: Draw the structural formula for 2-butanol:
Note: All sections of this
report, except the structural
formulas, must be typed.
Page 1 of 7

DATA, CALCULATIONS AND GRAPHS
Pentane
Temperature (oC) Temperature (K) 1/Temp (1/K) Pvap (mmHg) Pvap (atm) ln Pvap
11.8 285.0 0.003509 341.80 0.44974 -0.7991
14.9 288.1 0.003472 361.50 0.47566 -0.7431
17.7 290.9 0.003438 381.50 0.50197 -0.6892
19.6 292.8 0.003416 401.50 0.52829 -0.6381
21.6 294.8 0.003393 421.50 0.55461 -0.5895
23.2 296.4 0.003374 441.50 0.58092 -0.5431
24.8 298.0 0.003356 461.50 0.60724 -0.4988
26.2 299.4 0.003341 481.50 0.63355 -0.4564
27.8 301.0 0.003323 501.50 0.65987 -0.4157
28.9 302.1 0.003311 521.50 0.68618 -0.3766
30.4 303.6 0.003294 541.50 0.71250 -0.3390
31.3 304.5 0.003285 561.50 0.73882 -0.3027
32.6 305.8 0.003271 581.50 0.76513 -0.2677
33.6 306.8 0.003260 601.50 0.79145 -0.2339
34.6 307.8 0.003249 621.50 0.81776 -0.2012
35.4 308.6 0.003241 641.50 0.84408 -0.1695
36.4 309.6 0.003230 661.50 0.87039 -0.1388
37.4 310.6 0.003220 681.50 0.89671 -0.1090
38.3 311.5 0.003211 701.50 0.92303 -0.0801
39.1 312.3 0.003203 721.50 0.94934 -0.0520
4 pts
2 pts
DHo
vap 21.09 kJ/mol
DSo
vap 66.84 J/(mol·K)
Type sample calculations for determining DH and DS for n-pentane.
Slope = -2536.5
Delta H = -Slope x R = -(2536.5) x 8.3145 J/molK x 1kJ/1000J = 21.0897kJ/mol
Intercept = 8.0387
Delta S = Intercept x R = 8.0387 x 8.3145 J/molK = 66.8378J/molK
.Place your plot of ln(Pvap) vs 1/T here (cover this instruction box so your graph is an appropriate size)
.Properly label your graph (labels for axes, including units, and a title)
Include a trendline and its equation and R2 value on your graph. This is done by right-clicking on one of the data points
on your graph and choosing "Add Trendline" from the drop down menu. The first tab asks what type of trendline you
.wish to use, and the Options tab allows you to include the trendline equation and R2 value
y = -2536.5x + 8.0387
R² = 0.9889
-1.0000
-0.9000
-0.8000
-0.7000
-0.6000
-0.5000
-0.4000
-0.3000
-0.2000
-0.1000
0.0000
0.003150 0.003200 0.003250 0.003300 0.003350 0.003400 0.003450 0.003500 0.003550
lnPvap
1/Temp (1/K)
Pentane: lnPvap vs. 1/T
Page 2 of 7