Tuesday AM, Group A6
Use redox titration with potassium permanganate (KMnO4) solution to analyze an unknown Iron II (Fe2+) solution.
Redox titration is a type of titration based on a redox reaction between the analyte and titrant in the reaction (Burk et al. 2011). In order to measure the iron content of an unknown iron sample, redox titration can be performed with Fe(II) solution and standardized potassium permanganate solution. In this case the analyte of the reaction is Fe(II) and the titrant is (KMnO4). In order for redox titration to proceed; no side reaction can occur, if the solution is not totally acidic then neutral solutions would cause it to produce MnO2 (Burk et al. 2011). A satisfactory indicator needs to be met to signify the ‘end point’ (Burk et al. 2011). It also needs to have a high rate of reaction such that when end point is reached it is apparent so no extra titrant is added to the mixture (Burk et al. 2011). At last, the reaction must be thermodynamically spontaneous enough in order for the stoichiometric calculations to be used validly (Burk et al. 2011). KMnO4 cannot be used as a primary standard; this is because it is not stable in the presence of air. It oxidizes sporadically to MnO2. For this reason, the primary standard used is sodium oxalate, Na2C2O4. The standardization of of KMnO4 solution with Na2C2O4 is as follows:
And the overall balanced equation: 16H++5Na2C2O4+ 2KMnO4→10Na++2CO2
These reactions are thermodynamically spontaneous, but the final one is susceptible to a side reaction and it is naturally very kinetically slow (Blandamer et al. 1998). The MnO2 present in the reaction in KMnO4 must be filtered to remove it because it interferes with the standardization. After KMnO4 has been standardized, Fe (II) can be titrated with KMnO4. Two of the side...