Iron Analysis By Redox Titration

702 Words3 Pages
Iron Analysis by Redox Titration Procedure In this experiment we are to determine the percentage of iron in our unknown containing Iron (II) Ammonium Sulfate, Fe(NH4)2 (SO4)2  6H2O, by redox titration. Potassium Permanganate KMnO4 is used as an oxidizing agent in volumetric analyses. In acid solution MnO4- undergoes reduction to Mn2+. 8H+ (aq) + MnO4- (aq) ⇌ Mn2+ (aq) + 4H2O Aqueous MnO4- solutions are violet and those of Mn2+ are nearly colorless, the equivalence point in titrations using potassium permanganate as the titrant can be taken as the first permanent pink that appears in the solution. In the reaction to determine percent of Iron in unknown the titration, which involves oxidation, is carried out in sulfuric acid solution. The end point of titration is marked if phosphoric acid present forms colorless complex with acid. Number of moles of KMnO4 is equal to product of the molarity of KMnO4 and volume used. Number of moles of iron present is obtained from balanced equation fro reaction and amount permanganate ion reacted. The procedure for the lab went as follows: 1. Obtain buret and the unknown iron (II) sample. 2. Weigh three samples of approximately one gram of unknown into 250mL Erlenmeyer flask and record weight. 3. Cleanse buret by quantitative rinse with KMnO4 4. Add 50mL of 1M Sulfuric Acid to one sample at a time and dissolve contents in flask completely. It was only to be added once we were ready to titrate the sample. 5. Immediately titrate iron solution with KMnO4 a. After solution turns yellow add 7.4mL of 6M Phosphoric Acid 6. Repeat with all samples Data Fe2+ (aq) + MnO4- (aq)  Fe3+ (aq) + Mn2+ Fe2+ (aq)  Fe3+ (aq) + 1e- (oxidation reaction) 5e- + MnO4- (aq)  Mn2+ (aq) (reduction reaction) 5e- + MnO4- (aq) + 8H+  5Fe3+ (aq) + Mn2+ (aq) + 4H2O (l)
Open Document