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Redox Titration Percent iron (II) in a salt by permanganate titration Objective The purpose of this experiment is to determine the % Fe in Ferrous{Fe(II)} form in a ferrous salt by redox titration against a strong oxidant, potassium permanganate. Sodium oxalate is used as a standard to standardize the solution of permanganate. Background Reactions that involve the transfer of electrons from one substance (the reducing agent) to another substance (the oxidizing agent) can be used in quantitative volumetric analysis. At the end-point of the titration the number of equivalents reduced must equal the number of equivalents oxidized, # equivalence in reduction = # equivalence in oxidation. Simply put, the number of electrons used in oxidation must equal the number of electrons used in reduction. The gram equivalent mass of a substance involved in an oxidation-reduction process is the number of grams reacting for 1 mole electron change. It is calculated from the molecular mass divided by the electron change per mole. Your oxidizing agent will be KMnO4 that in acid solution undergoes the reaction, MnO41- + 8 H+ + 5 e- ! Mn2+ + 4 H2O This reaction has a 5 e- change per mole of KMnO4 or gram equivalent mass equals onefifth the molecular mass. Potassium permanganate has deep purple color and thus functions as it's own indicator when being reacted with colorless substances. The MnO41- ion is violet and the Mn2+ produced is colorless. Therefore if the KMnO4 is the titrant, the end point is the first permanent pink color in the titration mixture. Note: It is important that permanganate titration be done in acidic solutions as it forms other products in neutral or basic solutions. Solid KMnO4 cannot be obtained in a high state of purity so a standard solution cannot be made directly from the mass of KMnO4 and volume of solution. Moreover, KMnO4 tends to react with organic residues in water. You will make a solution of approximately the concentration needed and then standardize...
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