Evaporation and Intermolecular Attractions PDF

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Evaporation and Intermolecular Attractions

Purpose This lab investigates the temperature changes caused by the evaporation of liquids. The temperature changes, and intermolecular forces will be used to predict and measure the temperature for several other liquids. Procedure The procedure for this lab can be found on pages 19-21 in “General Chemistry CHE111L Lab Manual Spring 2020” Data Tables Carbon copies of data tables have been attached to the back of this lab report. Calculations ΔT (°C) = Tinitial – Tfinal Ethanol: ΔT = 22.3°C - 11.5°C = 10.8°C 1-propanol: ΔT = 22.3°C – 8.4°C = 13.9°C 1-butanol: ΔT = 22.2°C – 17.2 = 5°C n-pentane: ΔT = 22°C - -0.7°C = 22.7°C methanol: ΔT = 22.6°C – 2.5°C = 20.1°C Acetone: ΔT = 22.2°C – 0.5°C = 21.7°C n-hexane: ΔT = 22.2°C - 7.6°C = 14.6°C 2-butanone (methyl ethyl ketone): ΔT = 22.2°C - 8.6°C = 13.6°C Summary of Results Substance Molar Mass (grams/mol ) ethanol 46.069 1-propanol 60.096

ΔT(T1-T2) (°C) 10.8 13.9

1-butanol

74.123

5

n-pentane

72.151

22.7

Methanol

32.042

20.1

Acetone

58.080

21.7

n-hexane

86.178

14.6

2-butanone (methyl ethyl ketone)

72.107

13.6

Predicted ΔT (°C) Lower than 1-propanol Higher than 1-butanol Higher than ethanol Higher than n-propanol Lower than pentane Lower than acetone

Explanation 1-butanol has a higher molecular weight n-pentane has a lower IMF molecular weight of methanol is less than molecular weight of ethanol Acetone has a lower molecular weight Molecular weight of hexane is greater than the molecular weight of pentane Methyl ethyl ketone has a higher molecular weight

Conclusion The purpose of this lab is to investigate the temperature changes caused by the evaporation of several liquids. Using these results, and the intermolecular forces that are present, the temperature change for several other liquids will be predicted and measured. In the graph, series that have hydrogen bonding tend to have a lower change in temperature value. The two lowest points on the graph were Ethanol and Butane, both alcohols hold dipole-dipole bonds and hydrogen bonds. On the other hand, acetone and pentane are the two highest points on the graph, and both lack hydrogen bonds. Sources of error that might’ve occurred during this experiment is the variability in paper tightness, air currents, and the ΔT value for propanol. If the paper isn’t tight enough around the probe, it can cause a false ΔT reading, and in turn can affect the trendline in the graph. In this lab the change in temperature value for propanol is considered human error, because it does not go in line with the rest of the alcohols tested in this experiment.

Post-Lab Questions Use your graph to calculate equations of the lines connecting your data points for alkanes and ketones. Then calculate change in temperature (ΔT) for the following compounds (show calculations): 1. Butane, CH3CH2CH2CH3 a. Molecular weight = 58.12 g/mol b. Y = 8.1/-14 (58.12) + 64.4 c. Y= 30.77 °C d. ΔT = 30.77 °C 2. 3-pentanone, CH3CH2(CO)CH2CH3 a. Molecular weight = 86.13 g/mol b. Y = 8.1/-14 (86.13)+ 63.4 c. Y = 13.57 °C d. ΔT = 13.57 °C Alkanes: (Y1-Y2/ X1-X2) Slope: 22.7°C - 14.6 °C / 72g/mol – 86g/mol = 8.1/-14 22.7= (8.1/-14) (72) + b B = 64.4 Y = 8.1/-14 x + 64.4 Ketones: (Y1-Y2/ X1-X2) Slope: 21.7°C -13.6 °C / 58g/mol – 72g/mol = 8.1/-14 21.7 = (8.1/-14) (72) + b B = 63.4 Y = 8.1/-14 x + 63.4...