CHEMISTRY_COLA_LAB_REPORT - Analysis of Phosphate Content...

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Analysis of Phosphate Content in Colas. David Petronio Chemistry 101 Laboratory, Section 33 Instructor: Sushant Sahu November 7, 2007. My signature indicates that this document represents my own work. Outside of shared data, the information, thoughts and ideas are my own except as indicated in the references. ____________________________________________
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Abstract The following report is an analysis of phosphate concentration in Coke, Diet Coke, and Dr. Pepper. Initially, the relationship between the color of a compound substance and the wavelength of light it absorbs was determined by analyzing several dyes under a spectrophotometer. Known phosphate concentrations ranging from .00012 M to .00018 M were used to find a correlation between the absorbance of light and the concentration of the phosphate compound. A lambda max of 370 nm was used to evaluate the phosphate concentrations because this wavelength value yielded the maximum absorption under the spectrophotometer. During the final phase of the experiment, the three colas were diluted, combined with ammonium vanadomolybdate and then analyzed under the spectrophotometer at the lambda max. The absorbance values were used in the trend line equation “y = 0.107x + 0.549”, which correlates absorbance of phosphate to concentration of it. The findings justify the conclusion that Coke had the highest concentration of phosphate with a .61 M concentration, while Diet Coke had the lowest concentration at .58 M. Introduction The goal of this laboratory experiment was to determine the relationship between the color of a compound, and the wavelength of light absorbed. (Cooper, p. 129) More importantly, the ultimate goal of the experiment was to determine the concentration of phosphate in three colas; Coke, Diet Coke and Dr. Pepper. Students were placed in a theoretical situation where they were conducting research for a major cola company and needed to investigate the phosphate content of rivals’ colas. Since it is believed the buffering capacity of phosphate helps settle upset stomachs, many people turn to phosphate-rich colas. (Cooper, p. 129) Thus, information on phosphate content of rivals’ cola might help to formulate a more marketable product. At first, experimenters needed to correlate the amount of light absorbed by each cola with the concentration of phosphate in that cola. The initial phases of the procedure required that the experimenters become familiar with the spectrophotometer. Red, blue, a red-blue mixture, and potassium permanganate were utilized in the first step of the procedure by analyzing them under the Spec 20. Using the lambda max of phosphate, several concentrations of phosphate were evaluated and a correlation trend line was graphed. The colas were diluted and combined with ammonium vanadomolybdate to be analyzed under the Spec 20. Phosphate, alone, cannot be analyzed because it does not absorb UV or visible light; however, when combined with potassium vanadomolybdate, it produces a color (wavelength) which can be evaluated under the spectrophotometer. Once all the readings were taken, their concentrations were found by entering absorbance values into the previously formulated trend line equation for concentration.
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This note was uploaded on 04/07/2008 for the course CHEM 101 taught by Professor Rillings during the Fall '06 term at Clemson.

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CHEMISTRY_COLA_LAB_REPORT - Analysis of Phosphate Content...

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