Introduction
Our Laboratory project was conducted in order to determine the phosphate concentration present in three brands of colas in the form of phosphoric acid. The concentration of phosphate in colas is important due to its ability to sooth an upset stomach, but also block absorption of calcium and lead to Osteoporosis. In the first phase of our investigation, we analyzed a series of colored solutions using a Spectronic 20. The second phase of our experimentation lead us to the investigation and analysis of our three brands of cola. We went about our investigations by incorporating a number of procedures outlined in the Cooperative Chemistry Lab Manual with our own knowledge of the subject at hand.
The goals of our experiments were twofold. Our initial goal was to familiarize ourselves with the Spectronic 20, understand the relationship between the amount of absorption and the color spectrum (Lambda max), and comprehend the relationship between the absorption of light and concentration of solution (Calibration curve). The knowledge acquired in the first phase of our experiments aided us in reaching our second goal. Our second, and most important, goal of the experiment was to find the phosphate concentration in Mountain Frost, Coke, and Dr. Perfect, and investigate these results. We expect to find that the phosphate concentrations of the colas are proportional to the color and transparency of the various samples, but that there is not enough phosphate concentration existent in a cola to be deemed as harmful.
Results
In phase one of experimentation, the lambda max of the blue solution proved to be 490 nm, while yellow solution reached lambda max at 600 nm, and green at 520 nm. The permanganate solution reached lambda max at 530 nm, and structuralized into a upward sloping calibration curve. Refer to table one and Chart 3.A for depiction.
Color Lambda Max
Yellow 600 nm
Blue 490 nm
Green 520 nm
In phase two of experimentation, the lambda max of the 1 x 10-4 M solution (chosen solution) proved to be 395 nm. The resulting calibration curve ranged from 0.0009 M concentration at 0.3 absorbance to 0.005 M concentration at 1.7 absorbance. Coke had an 8% transmittance, which coincides with a concentration of 0.004 M. Dr. Perfect had a 4% transmittance, which gave it a 0.008 concentration. Mountain Frost had an 86% transmittance, which was too high to show up on the calibration curve. These results can be reviewed on table three and graph 3.B for details.
M1V1=M2V2
Solution Stoicheometry Required Stock
A Permanganate Stock 1.25 ml KMNO4.
0.0003 M 3 ml Stock
0.0005 M 5 ml Stock
0.0007 M 7 ml Stock
0.0009 M 9 ml Stock
B Cola Stock 1.24 ml KH2PO4
1 x 10-3 M 2 ml Stock
1 x 10-4 M 0.2 ml Stock
5 x 10-4 M 1 ml Stock
1 x 10-5 M 0.02 ml Stock
9 x 10-5 M V1=0.18 ml Stock
Word Count: 483
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