Chem- IMF Lab - IMF lab exercise PDF

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IMF lab exercise...

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LABORATORY REPORT

EXPERIMENT: Intermolecular Forces Name: Ishaa Kulkarni Partner: Data provided by prof C Lab Section: D09 Date Experiment Performed: Wednesday, January 27, 2021 1. Hypothesis: During the experiment of intermolecular forces, the hypothesis of the lab was to investigate the relationship between intermolecular forces and evaporation. Liquids with more molecular weight will possess stronger intermolecular forces and therefore there would be a decrease in rate of evaporation. 2.

Complete the following tables.

Table 1 Determination of [NaOH] Substance Tmax (°C) Tmin (°C) ΔT = Tmax - Tmin (°C) Ethanol 22.8 15.5 7.3 1-Propanol 22.7 18.5 4.2 Table 1 shows the temperature change of substance ethanol and 1-Propanol. Data was provided by professor Carnevale.

Table 2 Moles of Acetic Acid Molecular Weight Substance Tmax (°C) Tmin (°C) (g/mol) ΔT = Tmax - Tmin (°C) Methanol 32.04 g/mol 24.8 8.5 16.3 1-Butanol 74.12 g/mol 24.4 23.3 1.1 Pentane 72.15 g/mol 23.6 -4 27.6 Hexane 86.18 g/mol 24.9 8.9 16.0 Acetone 58.08 g/mol 24.2 1.7 22.5 Water 18.01 g/mol 25.8 20.1 5.7 Table 2 shows the temperature changes and molecular weight of substances Methanol, 1-Butanol, Pentane, Hexane, Acetone, and Water. Data was provided by Prof C.

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3. Create the x-y scatter graph of Molecular Weight (x) vs ΔT (y) for the four alcohol molecules (Methanol, Ethanol, Propanol, and Butanol). Be sure to label your axes and provide a figure caption.

Temperature Change During Evaporation 18 16 14

△T (℃)

12 10 8 6 4 2 0 30

35

40

45

50

55

60

65

70

75

80

Molecular Weight (g/mol) Ethanol

1-propanol

Methanol

1-butanol

Give a brief statement (2 sentences) on the observed trend and if it does/does not match your predictions. It is observed that as the molecular weight of the of the liquid increases, there is a decrease in the △T. The trend does match our predictions since increase in molecular weight will cause increase of dispersion force and therefore decrease in vapor pressure. a.

4. Calculations (Use equation function in Word to show your calculations. One example for each type of calculation is sufficient. Be sure to look at the example lab report provided on Canvas to see how your calculations section should be formatted.)

Tmax - Tmin (°C) = ΔT Ethanol: 22.8 – 15.5 = 7.3 °C

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5. Conclusion (Give a brief summary of your final result(s) and if it met your predictions/hypotheses.) In this experiment it can be concluded that substances with weak intermolecular forces such as London dispersion force will show higher rate of evaporation. When the bonds between a compound are considered to be weak then it is very easy for the liquid substance to evaporate. When the liquid substance evaporates at a higher rate, it also possesses a decrease in temperature. During the experiment butanol with molecular weight of 72.04 g/mol has weak intermolecular force such as the London dispersion force, therefore it evaporates at a higher rate and has a △T of 1.1 °C. The experiment also supports our hypothesis there is a relationship between intermolecular forces and evaporation rate and therefore, it can be concluded that substances with higher molecular weight and strong LDF will possess slow rate of evaporation leading to a decrease in △T. 6. Error Analysis (Briefly describe any errors that would have caused deviations in the data. There is no such thing as no errors.) The error analysis that could have taken place during the experiment can be poor calibration of the probe which can lead to inaccurate results. Another error that could have happened was loose fitting of the filter paper on the temperature probes. This can lead to misreading of the temperature and therefore will affect the evaporation rate. 7. Citations (Give a proper citation for any sources used. At minimum, you must cite the lab manual.) Beran, J. A. (2014). Laboratory manual for principles of general chemistry. Hoboken (N.J.): Wiley. 8. Post Lab Questions (Complete questions 2 through 6) 1. Alkanes: Hexane < Pentane Alcohols: Butanol < Propanol < Ethanol < Methanol 2. Largest ΔT values mean that the sample does evaporate readily. Small ΔT values mean that the sample does not evaporate readily.

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3. The only difference that would be observes looking at the formulas for the alkanes used in this experiment would be the number of hydrogen and carbon molecules present in each. Hexane has 6 carbons and 14 hydrogen whereas pentane has 5 carbons and 12 hydrogens. 4. The intermolecular forces that are present in hexane and pentane are London dispersion forces (LDF). 5. The only difference between the alcohol’s formula is the number of carbon and hydrogen molecules present in each. Methanol has 1 carbon and 3 hydrogen, ethanol has 2 carbons and 5 hydrogens, propanol has 3 carbons and 8 hydrogens, and butanol has 4 carbons and 10 hydrogens. 6. The intermolecular forces observed in the alcohols used during this experiment is London dispersion force (LDF) and Hydrogen bonding where a hydrogen molecule is attached to an oxygen with lone pair.

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