Report 10 - 1 Spectrophotometric Determination of Manganese...

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Spectrophotometric Determination of Manganese and Chromium in a MixtureVincent GalloCHM3120C-903April 14th20161
I. IntroductionSpectrophotometric techniques can be used to simultaneously determine the concentration of binary mixtures as long as there is no significant interaction between the two parts. Spectrophotometry is a common analytical technique used in order to measure the amount of light a sample absorbs. When a photon of light interacts with an analyte, the absorption of the photo reduces the total number of photons, leading to a decrease in the intensity of the light beam. Measuring this difference in light intensity can be read as absorption through a spectrophotometer. In this experiment, simultaneous spectrophotometric determination of the concentrations of manganese and chromium was completed using a spectrophotometer. The issue is that the absorption spectra of permanganate and dichromate overlap. Manganese and chromium ions by themselves do not absorb a significant amount of light,therefore, the metals were oxidized into Cr2O72-and 2MnO4-, respectively. The ions were oxidized according to the following reactions:+¿2¿+14H¿2¿+6SO4¿∆, Ag+¿Cr2O7¿2¿+7H2O→¿3+¿+3S2O8¿2Cr¿+¿¿+6H¿¿+5I O3¿¿+3H2O→2MnO4¿2+¿+5I O4¿2Mn¿2
II. Experimental ProcedureStandardized MnSO4 and K2Cr2O7 were obtained from the TA and placed each into a 150 mL beaker. Then, 50 mL of distilled water was transferred into a 100 mL volumetric flask. Then, 2.8 mL of concentrated H2SO4 was added to the volumetric flask, then the mixture was diluted to the mark. The spectrophotometerwas allotted 30 minutes to warm up, and then it was calibrated for a wavelength of 440nm. Following this step, MnSO4 was distributed into three 250 mL Erlenmeyer flasks in 10mL, 15mL, and 25 mL aliquots. Distilled water was then added until 50 mL was reached. After this, 10mL of concentrated H2SO4 was
added to each flask, along with .5g of solid KIO4. Each of these mixtures was heated to boiling for 10 minutes, and then transferred into 250 mL volumetric

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