Module #5 Formal Post-Lab Report

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MODULE #5 FORMAL POST-LAB REPORT 0 Module #5 Formal Post-Lab Report Evan Dangler Chem 2045L Dr. Laura Anderson October 27, 2022

MODULE #5 FORMAL POST-LAB REPORT 1 Introduction: Discuss visible spectrum and the colors. Discuss the concept of UV-vis spectroscopy. Discuss the purpose of a calibration plot. Discuss Beer's Law The goal of this experiment is to create a calibration curve of the absorbance of 3 major food dyes that will allow us to find and relate the absorbance of commercial products. One of the main things used in this lab is the visible light spectrum. Humans see different colors of visible light due to different wavelengths of light (Visible Light | Science Mission Directorate, 2016). Different wavelengths will cause us to see different colors. This pairs with Ultraviolet–visible spectroscopy. Ultraviolet–visible spectroscopy is a quantitative technique used to measure how much a chemical substance absorbs light (UV Vis Spectroscopy | UV Vis Spectroscopy Applications | Edinburgh Instruments, n.d.). Once we have successfully measured this data paired with the absorbance of liquids, we can create calibration plots with the data. A calibration plot allows us to find a trend line of our data that will let us predict different absorbance levels of similar substances without having to measure of preform an experiment. In order for any of our numbers to make sense, we need to use Beer’s Law. Beer’s Law tells us that the amount of energy absorbed or transmitted by a solution is proportional to the solution's molar absorptivity and the concentration of solute (Illustrated Glossary of Organic Chemistry - Beer's Law (Beer- Lambert Law), n.d.). With these methods and information, we are successfully able to complete our experiment. Experimental Methods: We split this lab in to two weeks. During the first week, we started by ensuring that all of our PPE was on before beginning the lab. The goal of the lab was to create a calibration curve of

MODULE #5 FORMAL POST-LAB REPORT 2 the absorbance of 3 major food dyes. We started that process by obtaining the 3 dyes (Red, Blue, Green). For each dye, we measured out 10ml of the dye using a pipet and graduated cylinder and put it in a volumetric flask, making sure to rinse out any extra dye left in the graduated cylinder into the volumetric flask with distilled water. We then added distilled water until we reached 100ml. We then made sure that the solution we created was mixed well before pouring it into a beaker. We repeated this process 5-6 times using the solution we previously created as the starting solution each time. Once we did this for all 3 dyes, we moved on to finding the absorbance and wavelength of each level of concentration. We did this by using the spectrophotometer. We started by calibrating the spectrophotometer with a cuvette filled with distilled water and one that was black. We then measured the absorbance of each of the levels of concentration for each dye, using the same wavelength for all concentration levels of each dye. We recorded this information and made a calibration curve graph in Excel with the data we collected. For the second week of this lab, we found the absorbance level of 2 liquid substances we brought into class with us. We used the same dyes as last week in our substances. We then used the spectrophotometer to find the absorbance of the substances using the same lambda max as we calculated in week one. We repeated this process 3 times for each substance. We then compared our results from the substances to the results we got last week. Results: Table 1. Parallel Dilution Data Sampl e Sample Concentration (M) Stock Volume (mL) Di Water Volume (mL) Total Volume (mL) 1 2.5 × 10 − 5 5mL 5mL 10mL

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MODULE #5 FORMAL POST-LAB REPORT 3 2 2 × 10 − 5 4mL 6mL 10mL 3 1.5 × 10 − 5 3mL 7mL 10mL 4 1 × 10 − 5 2mL 8mL 10mL 5 5 × 10 − 6 1mL 9mL 10mL Table 2. Blue Dye #1 Data Blue #1 (λ=626.3) Absorbance Concentration (M) 5 mL 1.39 2.5 × 10 − 5 4 mL 1.19 2 × 10 − 5 3 mL 0.98 1.5 × 10 − 5 2 mL 0.59 1 × 10 − 5 1 mL 0.24 5 × 10 − 6 Table 3. Green Dye Data Green (λ=614.6) Absorbance Concentration (M) 5 mL 1.17 2.5 × 10 − 5 4 mL 1.09 2 × 10 − 5 3 mL 0.96 1.5 × 10 − 5 2 mL 0.67 1 × 10 − 5 1 mL 0.25 5 × 10 − 6 Table 4. Blue Powerade (λ=626.3) Trial Absorbance Concentration (M) 1 0.27 4.4 × 10 − 6 2 0.25 4.8 × 10 − 6 3 0.38 3.2 × 10 − 6 Concentration Calculations: 5 × 10 0.24 × ( ¿¿ − 6 )= 0.27 x x = 4.4 × 10 − 6 ¿

MODULE #5 FORMAL POST-LAB REPORT 4 5 × 10 0.24 × ( ¿¿ − 6 )= 0.25 x x = 4.8 × 10 − 6 ¿ 5 × 10 0.24 × ( ¿¿ − 6 )= 0.38 x x = 3.2 × 10 − 6 ¿ Table 5. Green Gatorade (λ=614.6) Trial Absorbance Concentration (M) 1 0.35 3.6 × 10 − 6 2 0.25 5.0 × 10 − 6 3 0.27 4.6 × 10 − 6 Concentration Calculations: 5 × 10 0.25 × ( ¿¿ − 6 )= 0.35 x x = 3.6 × 10 − 6 ¿ 5 × 10 0.25 × ( ¿¿ − 6 )= 0.25 x x = 5.0 × 10 − 6 ¿ 5 × 10 0.25 × ( ¿¿ − 6 )= 0.27 x x = 4.6 × 10 − 6 ¿

MODULE #5 FORMAL POST-LAB REPORT 5 Discussion: The linier equation on the calibration curve is the slope equation of the trend line on the graph. This allows us to calculate the absorbance of the substance when given the concentration or vice versa when plugging in the values. This allowed me to calculate the concentration of our commercial product. Another important value on the graph is the R-squared value. The R-square value represents how accurate the trend line on the graph is. The closer to 1, the more accurate. However, a low R-squared value can cause some potential errors in future calculations. For example, a graph with a low R-squared value is likely to be off on their calculation of concentration. To help prevent any other potential errors, I would do the experiment a little differently if I were to do it again. If I were to repeat this experiment again, I would use the same cuvette each time while finding the absorbance of our solution to keep from having any inaccuracy caused by smudging or differences in the equipment. Conclusion: In conclusion, the experiment we performed in the lab was a success and gave us some quality results. We were able to successfully create a parallel dilution with both of the dyes. We

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MODULE #5 FORMAL POST-LAB REPORT 6 were also able to find the absorbance levels of the different levels of dilution. Our data was correct and accurate due to us preforming the experiment well. We successfully created calibration curves that allow us to estimate data without preforming all of the test. We also were able to calculate the absorbance of our commercial product and relate them to the data from the experiment. In the end, we were able to complete all the tasks required for this experiment. References: UV Vis Spectroscopy | UV Vis Spectroscopy Applications | Edinburgh Instruments. Edinburgh Instruments, n.d. https://www.edinst.com/techniques/uv-vis-spectroscopy/#:~:text=UV- Vis%20Spectroscopy%20(or%20Spectrophotometry,a%20reference%20sample%20or %20blank. (accessed 2022-10-26). Visible Light | Science Mission Directorate. Science Mission Directorate | Science, August 10, 2016.https://science.nasa.gov/ems/09_visiblelight#:~:text=WAVELENGTHS%20OF %20VISIBLE%20LIGHT&text=As%20the%20full%20spectrum %20of,wavelength,%20at%20around%20700%20nanometers. (accessed 2022-10-26). Illustrated Glossary of Organic Chemistry - Beer's Law (Beer-Lambert Law). UCLA – Chemistry and Biochemistry, n.d. http://www.chem.ucla.edu/~harding/IGOC/B/beers law.html#:~:text=Beer's%20Law%20(BeerLambert%20Law):%20The%20amount%20of %20energy,a%20more%20dilute%20solution%20does . (accessed 2022-10-26).