Lab Report 02 - Russell

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Drexel University *

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Feb 20, 2024

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Nalo Russell Experiment 2 - Distillation Fill in the blanks in the given template. Use underlines, boldface, or parentheses to clearly indicate the filled content within the context. Type up the report and save it as one single file in the PDF format. Submit the PDF file by the deadline. Key Observations Part A - Volume of methanol 13 mL in the distillation pot to distill. - Power of the heating mantle used during the distillation ≅ 40-50% . - Collected distillate: volume 10 mL , color clear , bp range 61° - 66 ° C. Part B - Volume of 50:50 methanol-water 13 mL in the distillation pot to distill. - Power of the heating mantle used during the distillation ≅ 50% . - Collected distillate: volume 10 mL , color clear , bp range 69° - 99° C. Part C - Volume of 50:50 methanol-water 13 mL in the distillation pot to distill. - Power of the heating mantle used during the distillation ≅ 50% . - Collected distillate: 10 mL - Fraction 1: volume 1 mL, bp range 66° C . - Fraction 2: volume 3 mL, bp range 68° - 80° C. - Fraction 3: volume 1 mL, bp range 87° C. - Fraction 4: volume 4 mL, bp range 92° - 98° C. - Fraction 5: volume 1 mL, bp range 98°C.

Results Insert graph 1: bp vs volume from part A. (An excel plot should occupy the majority of a properly scaled and labeled X-Y coordinate plane. All data points should be marked and connected with a trendline. Provide a title that gives a brief and clear description of the graph, and a caption that gives a more detailed description of the graph).

Insert graph 2: bp vs volume from parts B and C. (Combine both plots in the same coordinate plane. Follow the instructions for graph 1).

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Attach a copy of each GC spectrum.

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Fill in the GC result table below with the data from the GC spectra and your lab notebook. % Area of Methanol % Area of Water Boiling Point ( ° C) Fraction 1 88.03 11.50 66° Fraction 3 81.61 18.39 87° Fraction 5 2.81 97.19 98° Discussion Compare the separation efficiency of simple distillation vs fractional distillation. Your discussion should be entirely based on your own experimental data. Focus on the major differences in shapes of the two plots in graph 2 and their implications in efficiency of the two separation methods.Comment on the effectiveness of your distillation in separation of the methanol/water mixture in Part C. You should first assess the purity of each fraction based on the experimental data in the GC result table, then compare each to the expected outcome, and finally offer the conclusion on the overall effectiveness of your distillation. From my experiment, I not only noticed that fractional distillation was a longer process, but also that the temperature range is much wider than in simple distillation. While the intensity of the heating mantle was a bit lower during the fractional distillation; yet, the process still took longer over all, possibly with less accuracy. I believe the differences in the shapes of the graph originate from (1) the fluctuating changes in temperature due to chemical differences; and (2) the physical structure of the distillation assembly also causing temperature differences. First, I noticed that the thermometer would rise as the vapors of the methanol (lower-boiling compound) filled the head of the distillation assembly. The temperature would then drop, because the methanol would finish distilling before the vapors of the water (higher-boiling component) can fill the distillation head, which could create this inconsistency with temperature. Second, the fractional distillation assembly consists of a column that is used to enhance the separation process. The column provides a large service area for the vapor to rise through and complete multiple vaporization-condensation cycles. In fractional distillation there is additional surface area and interactions with the column create more opportunities for the lower boiling point components to vaporize and condense multiple times. While this results in a more effective and precise

separation, the ways through which I conducted the experiment created a greater temperature range. List three most important things you have learnt from this experiment and explain how they will help you carry out some form of distillation in the near future. 01. I learned the importance of heat control and how to slowly distillate. I was originally very quick to just crank up the power controller so that the water, with a much higher boiling point, can begin distilling; however, I realized that this is not always the most effective way. The distillation process is slow and requires patience and precision, which I will exercise in the future. 02. I learned the relevance of having a boiling point range. I first assumed that the boiling process occurs at a defined temperature every single time. Yet, this experiment has taught me the nuances with boiling point, and that this transitional phase takes place over a few degrees celsius. In the future, I will now treat boiling point as a range, rather than an exact value. 03. I learned that it is difficult to completely eyeball militer values in a erlenmeyer flask or a 1-dram vial. With that said, I learned to either count about 20 drops per mL, or to continue to practice measuring out mLs in a graduated cylinder or beaker. Over time, I hope to cultivate my eyeballing skills, so that I can more effectively measure such small amounts during the distillation process. Post-Lab Questions for Experiment 2 1. Specify whether a simple distillation or a fractional distillation would be more suitable for each of the following purifications, and briefly justify your choice. (a) Preparing drinking water from sea water. Simple distillation → This process would involve heating the sea water and selectively collecting the vaporized water, leaving behind the non-volatile components, which is most like salt and sand. Since water boils at 100°C and salt boils at 1,465° C, there is a substantial difference, making simple distillation a more effective method to create purified drinking water.

(b) Separating benzene, bp 80°C (760 torr), from toluene, bp 111°C (760 torr). Fractional distillation → Given the close proximity of their boiling points, fractional distillation is used to separate these components through multiple vaporization-condensation cycles. This results in distinct fractions of the solution. (c) Obtaining gasoline from crude oil. Fractional distillation → Crude oil is a very complex mixture of many hydrocarbons with varying boiling points. I assume that the process of obtaining gasoline from crude oil would involve countless cycles of vaporization-condensation in order to separate out the many compounds within the crude oil. While the oil may have several volatile components with similar or different boiling point ranges, it is still best to undergo multiple cycles of purification to obtain gasoline. (d) Removing diethyl ether, bp 35°C (760 torr), from p -dichlorobenzene (s), mp 52.3°C. Simple distillation → This technique relies on the selective boiling and condensation of diethyl ether and p -dichlorobenzene considering their distinct boiling points. This temperature difference should be considered substantial, vaporizing the diethyl ether (lower-boiling component) and collecting the vapor in a condensed form. 2. A student assembles a simple distillation apparatus. He uses a 25-mL round-bottomed flask for the pot, adds 10 mL of liquid to be distilled and a boiling chip, and attaches a head to the pot. He attaches a thermometer adapter to the head and inserts a thermometer. Next he attaches a condenser to the head and a receiver tube to the condenser. Finally, he attaches condenser hoses to the condenser, turns the water on, and starts heating. What big mistake did this student make and what might be expected to happen? The student forgot to insert the tube adaptor in between the condenser and receiver which allows for air to be released to prevent the build up of pressure. Also, the student turned the water on after attaching the tubes. Rather, he should check the water flow first, to get a gauge of the water flow before attaching. Last, he did not use the clips to ensure proper attachment, so the vial may slip off.

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3. Students A and B conducted part C of experiment 2, “Fractional Distillation of a Methanol - Water Solution”. The GC analysis of fractions 1 (F1), 3 (F3) and 5 (F5) collected by each of them is shown below. Answer the following question based on the GC data. Ignore the difference in response factor between methanol and water. (a) Choose any one of the gas chromatograms and assign the peaks based on the retention time. The peak at a retention time of approximately 3 minutes corresponds to water; and the peak at around 2.6 minutes aligns with the methanol. (b) Justify your peak assignment in (a) based on the GC theory alone, ignoring the compositions of the fraction. GC chromatography is used to separate and detect the chemical components, and the compound extract first typically has the lowest boiling point. Within the solution, methanol has a lower boiling point; thus, methanol would display a low retention time and would be extracted/ come out faster than water. (c) Compare the results of these two distillations to the expected outcome of a perfect distillation and explain why student B has done better than student A. Fraction Student A Student B F1 94% methanol + 6% water 98% methanol + 2% water F3 88% methanol + 12% water 95% methanol + 5% water F5 23% methanol + 77% water 1% methanol + 99% water Student A: The composition of the different fractions show that student A could properly remove the methanol from the 50:50 methanol-water solution in the early steps of fractional distillation when the temperature was low. Because student A’s final fraction 5 had a poor ratio between water content and methanol content, it becomes clear that their separation techniques were not as efficient or precise.

Student B: The percent of methanol in the distillate is higher and the trend is consistent for student B. They may have regulated the heating and the reflux ratio to achieve a more efficient fractionation. The GC profiles in the early fractions of distillation contain more methanol (lower boiling point) and the late fractions of distillation, when the distillation flask is subjected to comparatively high temperature, contain more of the water (higher boiling point). In fraction 5, only the high boiling water is present in maximum amounts and low boiling methanol is present in negligible amounts. Therefore, student B has achieved better separation of water and methanol from the 50:50 water-methanol solution using fractional distillation with greater efficiency. (d) Provide two possible causes and explain how they could lead to the poor-quality distillation by student A. Your explanation should be consistent with all the GC data. The possible cause to the poor-quality distillation by student A: - They have heated the mixture too fact to complete the distillation faster, but results in not ideal results - They may have helped the reflux ratio less than the required ratio. - They have used a fractionating column that has insufficient theoretical plates