1. The students determined the concentration of manganese in an ArthuZ pill through a series of dilution and analysis steps. They weighed pills, crushed them, made dilutions in nitric acid and phosphoric acid, and observed color changes after adding sodium periodate and heating. 2. The students then made a calibration curve using known concentrations of potassium permanganate and measured absorbance of their pill dilutions. 3. Their calculations determined the pill contained 2.718 mg of manganese, less than the labeled 4 mg, confirming their hypothesis. Proper analysis by supplement companies is needed to ensure accurate labeling.

2. Balance

3. Mortar

4. Beaker 250mL

5. 4.0M HNO3

6. Conc. H3PO4

7. Sodium Periodate

8. Heater

9. Volumetric flask of 10ml and 100ml

11. 2mL of the solution in volumetric flask, to another volumetric flask of 100ml and dilute with water.

12. Fill a 50mL of a burette at the 0.00 ± 0.001mL

14. The percent of the concentration of manganese in the pill was 0.004g1.2605 x 100 = 0.31%

15. Initial mass of the bottle:

16. It's supposed to be: 16.9305g - 0.6g = 16.3305

17. Experimental bottle weight: 16.3369g

18. Vitamin sample mass: 0.5936g

19. With HNO3 4.0M, the vitamin diluted and turn yellow.

20. Then, we filtrated the solution, added H3PO4 (conc.) and made 3 aliquote.

22. Absorbance = -log[64.6100] = 0.189767Y= 2.5139 x 103x + 1.9785 x 10-3<br />0.189767-1.9785 x 10-32.5139 x 103=x<br />7.47006762 x 10-5 = x<br />Calculation:<br />7.47006762 x 10 5(0.025L) (1mol Mn1mol KMnO4)100.00mL8.00mL(54.938g Mn1 mol Mn)=0.00128g in 0.5936g<br />0.00128g(1.2605g)0.5936g=x<br />0.002718g(1000) = x<br />2.718mg of manganese in ArthuZ = x<br />*After calculate the x with the graph, the mg of manganese in the pill is 2.718mg.<br />Conclusion<br />In conclusion, for every investigation that is going to be done in the scientific world there is a science that has the appropriate methodology to find what you are looking for. In this case our objectives were to find the concentration of manganese in a vitamin supplement pill. This was the main goal; the science that had the procedure and concepts necessary for this purpose was analytical chemistry. Analytical chemistry concentrates in the analysis of chemical components in materials. For that reason the other objective, determining the absorbance of various dilution of the tablet, was needed. Determining absorbency is the method that is used to determine concentrations of a sample. The hypothesis that we stated was that the concentration of manganese will result less than the quantity that the label says. To confirm this hypothesis an experiment was designed, it can be divided into three main parts: the first step of the process was the preparation of three aliquots that contain the dilutions of the pill, second step is the preparation of another eight aliquots with known concentration of manganese for comparison, final step is the measuring of the transmittance with the spec-20 and converting this results in to the milligrams of manganese present in the pill. After many calculations there was found 2.718mg of manganese. Our hypothesis was confirmed as true. The only possible error that could significantly affect the results is that in the filtration of the pill sample some of the pill was left behind. Besides that the results are very reliable. We can see that many pharmaceutical companies are not properly analyzing their products. Federal agencies should be stricter with the production of supplements. <br />References: <br />*Beran, J. A., “Chemistry in the laboratory”, 2nd ed., John Wiley & Sons: New York, 1996<br />*Chemicool –cooler than absolute zero [internet] {cited May 10,2011} Available from: http://www.chemicool.com/elements/manganese.html <br />*Quantitative Transfer [internet] {cited May 11, 2011} Available from: http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA6/MAIN/2QuantMenu/Transfer/MENU.HTM<br />* Silberberg, M. S. (2009) quot;
Chemistry: The Molecular Nature of Matter Changequot;
(5ta edición). McGraw-Hill.<br />