Chem I Lab Report Project 13

Chem I Lab Report Project 13 - Spectroscopic Analysis of...

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Unformatted text preview: Spectroscopic Analysis of Factors That Effect the Absorption of Light in a Compound to Determine the Phosphate Content of Cola Abstract This paper describes the results from the spectroscopic analysis of the factors that affect the absorption of light in a compound in order to determine the phosphate content of colas. Before beginning to determine the phosphate content of the Coca-Cola brand cola, the relationship between color and the wavelength of absorbance as well as the relationship between absorbance and the concentration of a solution had to be determined in order to find the phosphate content of the cola through spectroscopy. Through analyzing the absorbance of a yellow and green colored species with concentration held constant, it was found that the color of the solution depends on the wavelengths of light that remain after the other light is absorbed. Secondly, after analyzing the absorbance of light of differing concentrations of a 0.001M K 2 CrO 4 solution at the constant analytical wavelength, it was concluded that the absorbance of light and concentration were directly proportional. Using these two results, the group was able to test for the phosphate content in the cola sample using spectroscopy which resulted in a value of 9.5 x 10-5 moles of PO 4 per liter. Introduction The group was transferred to the research labs of a major cola company. The boss of the company asked the group to analyze many cola solutions using the new spectrophotometers that he just acquired. The goal of this project was to analyze the phosphate content of the cola sample through spectroscopy. In order to reach this goal, it was first necessary for the group to learn how to operate the Spec20. After this was accomplished the group then used the Spec20 to determine the relationship between the color of a compound and wavelength of light absorbed as well as the relationship between the absorbance of light and the concentration of a solution. Then, and only then, was the group able to determine the phosphoric acid content in the cola in order to report the results to the boss of the company. Results To compare the color of light absorbed versus the color of light remaining at given wavelengths (Table 1). 2 To determine the relationship between % transmittance and the absorbance of light in green colored species (Chart 1). Wavelength of absorbance maximum (nm) Color Absorbed Color Remaining (Color of solution) 380-420 Violet Green-yellow 420-440 Violet-blue Yellow 440-470 Blue Orange 470-500 Blue-green Red 500-520 Green Purple 520-550 Yellow-green Violet 550-580 Yellow Violet-blue 580-620 Orange Blue 620-680 Red Blue-green 680-780 Purple Green 3 Relationship Between % Transmittance and Absorbance in Green Solution 0.0 20.0 40.0 60.0 80.0 100.0 120.0 350 400 450 500 550 600 650 700 wavelength (nm) 0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700 0.800 0.900 1.000 Transmittance (%) Absorbtion transmittance absorbance To determine the relationship between % transmittance and the absorbance of light in yellow colored...
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Chem I Lab Report Project 13 - Spectroscopic Analysis of...

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