Experiment Report: Intermolecular Forces

1. Hypothesis

The alternative hypothesis (Ha) suggests that the alcohol with the highest molar mass will exhibit the lowest evaporation rate. The null hypothesis (H0) posits that the molar mass has no impact on the evaporation rate.

2. Tables

Table 1: Temperature Change During Evaporation

Table 2: Comparing Molecular Weight of Each Substance and Temperature Changes During Evaporation

3. Graphs

Figure 1: Change in Temperature Compared to Molecular Weight of Alcohols.

The line formed by the data points in the graph has a negative slope, indicating that as the temperature change decreases, the molecular weight increases. Therefore, the higher the molecular weight, the lower the temperature change, and the higher the evaporation rate, which aligns with our predictions.

4. Calculations

1. Temperature Changes (ΔT)

Temperature Changes (ΔT) were calculated using the formula:

ΔT = Tmax - Tmin

For each substance:

Ethanol: ΔT = 23.

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32°C - 13.73°C = 9.59°C

1-Propanol: ΔT = 23.77°C - 18.28°C = 5.49°C

Methanol: ΔT = 23.96°C - 5.97°C = 17.99°C

1-Butanol: ΔT = 23.82°C - 21.43°C = 2.39°C

Pentane: ΔT = 23.15°C - (-4.20°C) = 27.35°C

Hexane: ΔT = 24.85°C - 6.14°C = 18.71°C

Acetone: ΔT = 24.44°C - 2.00°C = 22.44°C

Water: ΔT = 24.08°C - 19.35°C = 4.73°C

2. Molar Mass (g/mol)

Molar masses were calculated using the atomic masses of elements present in each substance:

Methanol: 12.01 + 1.008 x 4 + 15.999 = 32.04 g/mol

Ethanol: 12.01 x 2 + 1.008 x 6 + 15.999 = 46.07 g/mol

1-Butanol: 12.01 x 4 + 1.008 x 10 + 15.999 = 74.12 g/mol

1-Propanol: 12.01 x 3 + 1.

008 x 8 + 15.999 = 60.09 g/mol

Pentane: 12.01 x 5 + 1.008 x 12 = 72.15 g/mol

Hexane: 12.01 x 6 + 1.008 x 12 = 86.18 g/mol

Acetone: 12.01 x 3 + 1.008 x 6 + 15.999 = 58.08 g/mol

Water: 1.008 x 2 + 15.99 = 18.01 g/mol

10. Conclusion

Based on the calculations in this laboratory report, we have confirmed the hypothesis that the alcohol with the highest molar mass exhibits the lowest evaporation rate. As shown in Figure 1, the line formed by the data points has a negative slope, indicating that higher molecular weight corresponds to lower temperature change and higher evaporation rate. Furthermore, 1-Butanol, with the highest molar mass (74.12 g/mol), also displays the lowest temperature change (2.39°C), making it the alcohol with the highest evaporation rate. This observation is consistent with the principle that the strength of Intermolecular Forces (IMFs) plays a crucial role in evaporation rates. Strong IMFs, such as hydrogen bonding present in alcohols due to the hydroxyl group, increase the energy difference between the liquid and gas phases, making it more challenging to evaporate and thus slowing the evaporation rate.

11. Error Analysis

One potential source of error that could have resulted in data deviations is the miscalibration of the probes.

12. Citations

Intermolecular Forces: Evaporation and Intermolecular Attractions [class handout]; Department of Chemistry and Physics, Nova Southeastern University: Fort Lauderdale, FL, 2010.

13. Post Lab Questions

2. Discover what the ΔT "tells" you about how readily a sample evaporates. Complete the following statements by adding in the blank the correct response:

Large ΔT values mean that the sample does evaporate readily.

Small ΔT values mean that the sample does not evaporate readily.

3. Look at the formula for your alkanes, what is the only difference between the formulas?

The only difference between the formulas is the number of carbons and hydrogens. Pentane has 5 carbons and 12 hydrogens, while Hexane has 6 carbons and 14 hydrogens.

4. What IMF(s) are present in the alkanes?

The IMFs present in the alkanes include London Dispersion forces and Dipole-Induced Dipole forces.

5. Look at the formula for your alcohols, what is the only difference between the formulas?

The only difference between the formulas is the number of carbons and hydrogens. Methanol has 3 hydrogens and 1 carbon, 1-Butanol has 4 carbons and 9 hydrogens, 1-Propanol has 3 carbons, 7 hydrogens, and 1 hydroxide, and Ethanol has 1 carbon and 3 hydrogens. Additionally, they all have one hydroxyl (OH) group, which characterizes alcohols.

6. What IMF(s) are present in the alcohols?

The IMFs present in the alcohols include Hydrogen Bonding, Dipole-Dipole forces, and London Dispersion forces.