Determination of Iron by Reaction with Permanganate-A Redox Titration Purpose:
The purpose of this experiment was to find the percentage of iron in an unknown iron oxide sample which could be determined through titration with a standard solution of potassium permanganate. Success in this analysis requires careful preparation and attention to detail. Performing this experiment also provides practice at titrations. The overall reaction is: 8H+(aq) + MnO4-(aq) + 5e- Mn2+(aq) + 4H2O
In acid solutions the permanganate ion undergoes reduction to manganese (2+) ion. Since the permanganate ion is violet and the manganese ion is colorless, the end point in the titrations using potassium permanganate as the titrant can be taken as the first permanent pink color that appears in the solution. This titration involves the oxidation of Fe2+ ions to Fe3+ ions by the permanganate ion, and is carried out in sulfuric acid solution to prevent the air oxidation of the ferrous ion. The end point of the titration is sharpened markedly if phosphoric acid is present. The reason being the Fe3+ ion by itself has a yellow color that can partly mask the pink endpoint, but the addition of phosphoric acid forms a colorless complex with the Fe3+ ion. Performing this lab requires patience and precision as well as a firm understanding of how to record accurate date (such as properly reading a buret). To complete the lab it is required to know how to convert from grams of a substance to moles of a substance, molarity, mole to mole ratio, calculating percent of a substance in a sample, and percent error. Also know that reduction and oxidation is what occurs in a redox reaction (Reduction is loss of oxygen. Oxidation is gain of oxygen).
Procedure: The procedure was the same as the handout with the exception that only 2 titrations were preformed. Data: (handwritten neatly and attached)
Results and Discussion:
The moles and mass of iron in each sample...
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