Chem162_IMForces_PartII_Report_042813

Value h o vap polar dominant intermolecular forces d

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value) H o vap (polar) Dominant Intermolecular Force(s) (D, P or HB) S o vap (J/mol·K) S o vap (J/mol·K) (Lit. value) Chem 162 Experiment #3: Intermolecular Forces Part II: Vapor Pressure and Enthalpy of Vaporization PURPOSE The purpose is to measure the enthalpies of vaporazation of pentane, diethyl ether, 2-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 (can be hand-drawn). Based on the structures, which molecule provides the dispersion forces component for itself and each of the others and what assumption is made in order to use the value for one compound to account for the dispersion forces in the others? (7 pts) N-pentane provides the dispersion forces component for itself and each of the others since it only exhibits London Dispersion. We can assume this is due to its nonpolarity and that it has similar bonding when compared to the other samples. Also because it only exhibits London Dispersion forces, this molecule's deltaH-vap is ideal for finding what fraction of other molecules deltaH-vap is due to London Dispersion forces. Similar molecular weight and polarizability to others. R esults and Discussion How do your enthalpies of vaporization compare with the literature values? How do your entropies of vaporization compare with the literature values? Discuss your results and include % error calculations. (2 pts) n-pentane: enthalpy of vaporization: (27.64-26) / 26 x 100% = 6.3% entropy of vaporization: (88.87 - 88) / 88 x 100% = 0.99% Overall, the percent errors for the enthalpy and entropy of vaporization for n-pentane were both very small, therefore our data obtained during lab proved to be very accurate when compared against the literature values.
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