Achem Postlab 10 wordd.docx - Spectrophotometric...

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Spectrophotometric Determination of Manganese and Chromium in MixtureJessi StrongCHM3120C- Lab 10Linda RoseIntroductionThere are different types of spectrophotometric methods that can be used in experiments, how-ever, we used absorption spectroscopy in this lab. We know we are using absorption spec-troscopy because we are measuring light as a function of wavelength. Spectrophotometers are used to determine absorbance at certain wavelengths. In this lab we are using absorbances 440nm and 545 nm. Our spectrophotometric skills will be determining manganese and chromium solutions according to Beers Law. After wavelengths and absorbances are obtained, acalibration curve is made at each wavelength for chromium and manganese to obtain the averagekvalue. We want to quantitatively determine the concentrations of dichromate ions and perman-ganate in a mixture.EquationsAg+2Cr3++ 3S2O82- + 7H2O    ⎯⎯→Cr2O72- + 6SO42- + 14H+Δ2Mn2++ 5IO4- + 3H2O    ⎯⎯→2MnO4- + 5IO3- + 6H+ΔAg+2Mn2++ 5S2O82- + 8H2O    ⎯⎯→2MnO4- + 10SO42- + 16H+Materials500 mL of unknown solution, 1 g of dried MnSO4H2O, 1.3 g of K2Cr2O7, 200 mL of conc.H2SO4, 20 g of solid potassium periodate (KIO4), 15 g solid potassium peroxydisulfate (K2S2O8),20 mL of 0.1 M of AgNO3, Spec20D, Kimwipe, parafilm, and the waste container.SafetyChemicalMnSO4K2Cr2O7H2SO4K2S2O8AgNO3
HazardsHazardous if incontact withskin, eyes, in-gestion or in-halationExtremely haz-ardous if incontact withskin. Can irri-tate eyes, skinor if ingestedVery hazardousif in contactwith skin, eyes,ingestion or in-halation.Very hazardousif in contactwith skin, eyes,ingestion or in-halationVery hazardousif in contactwith skin of in-gestion. Can ir-ritate eyes.

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