Chem 201 lab report 2 - Professor: SmithTA: Mathew Spire PDF

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Professor: Smith
TA: Mathew Spire ...

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Chem 201, Experiment 2 Taylor Herrera Analysis of a phosphate Lab Partner: Nicole September 14, 2017 Procedure See the pre-lab report for an outline of the general procedure. No changes from the procedure and-or the pre-lab. Experimental data Wavelength used for analysis: 375nm At of standard: 0.701 Ar of standard: 0.132 At of Fertilizer: absorbance 1: 0.600 absorbance 2: 0.585 absorbance 3: 0.586 At of drink: Name of drink Coke Gatorade

Calculated Results Fertilizer

Absorbance 1 1.110 0.646

Absorbance 2 1.205 0.672

Absorbance 3 1.080 0.641

Diluted c (M) Undiluted c (M) % P 2O 5

Trial 1 2.06 x 10^-4 6.18 x 10^-3 15.6%

Average %P2O5 Standard Deviation %P2O5

Trial 2 1.99 x 10^-4 5.97 x 10^-3 15.1%

Trial 3 1.99 x 10^-4 5.97 x 10^-3 15.1%

15.26% 0.28868

Drink Name/Type: Coke (regular)

Diluted c (M) Undiluted c (M) Mg phosphate/L

Trial 1

Trial 2

Trial 3

4.30 x 10^-4 1.29 x 10^-2 434.9626mg

4.7 x 10^-4 1.41 x 10^-2 475.372mg

4.17 x 10^-4 1.25 x 10^-2 421.429mg

Average mg phosphate/L Standard deviation mg phosphate/L

443.921 28.065

Name/Type: Gatorade

Diluted c (M) Undiluted c (M) Mg phosphate/L

Trial 1 2.26 x 10^-4 6.78 x 10^-3 228.416mg

Average mg phosphate/L Standard deviation mg phosphate/L

Discussion

Trial 2 2.37 x 10^-4 7.12 x 10^-3 239.970mg

231.524mg 7.295

Trial 3 2.24 x 10^-4 6.71 x 10^-3 226.194mg

1) The %P2O5 in the fertilizer for sample 1 was the highest with 15.6%. Sample 2 and 3 came out to 15.1%. The average percent for all three was 15.26%. The mg phosphate/L in the coke (regular) for sample 2 was the highest with 475.372mg. Sample 1 had 434.962mg and sample 3 had the lowest with 421.429mg. The average was 443.921mg. The mg phosphate/L in the Gatorade for sample 2 was also the highest with 239.970mg. Sample 1 had 228.41mg and sample 3 had the lowest with 226.194mg. The average was 231.524mg. 2) The stated fertilizer composition on the stock solution bottle is 15%, and all three of my samples for %P2O5 were very close to 15%. With that being said I think my results for that part of the experiment seem very reasonable. Since my standard deviation for %P2O5 is very low and below zero, that means that all of my samples were close to the same value and my data was precise. For the coke the standard deviation for mg phosphate/L was 28.065 which is pretty high indicating that my samples were spread out and not as precise. The Gatorade had a standard deviation of 7.295 which is still pretty high but my data is not as spread out as the coke. I wouldn’t say the data for the Gatorade is very precise though. According to livestrong.com, coca-cola has about 170mg in 1L. This is a huge difference between my data. Based off of that information my results do not seem reasonable. According to pepsicobeveragefacts.com, there are 104.260mg phosphate per liter. My data is almost double the amount that is actually in Gatorade, which means this data is not very reasonable either. 3) A possible error may be that each time I picked up the cuvette to change out the solutions, I touched it on the side with my hands and did not wipe it off each time. Fingerprints on the cuvette can ruin the reading and throw off your data by making the absorbance appear

higher or lower than it actually is. I may have prepared the solutions incorrectly throwing off the ratio or water and solution which would affect the absorbance readings. Since both the Gatorade and the coke were so much higher this is a likely source of error....