Permanganometry is one of the techniques used in qualitative analysis in Chemistry. It involves the use of permanganates and is used to estimate the amount of analyte present in unknown chemical substances. It involves two steps, namely the titration of the analyte with potassium permanganate solution and then the standardization of potassium permanganate solution with standard sodium oxalate solution. The titration involves volumetric manipulations to prepare the analyte solutions..
Depending on how the titration is performed, the permanganate ion can be reduced to Mnx, where x is +2, +3, +4 and +6. Using permanganometry we can estimate the quantitative presence of Fe+2, Mn+2, Fe+2 and Mn+2 when they are both present in a mixture, C2O42-, NO2-, H2O2 etc.
In the most cases permanganometry is performed in a very acidic solution in which the following reaction occurs:
MnO4- + 8H+ + 5e- = Mn+2 + 4H2O
The standard potential of this electrochemical reaction is Eo=+1.52 V, what shows that KMnO4, in an acidic medium is a very strong oxidizing agent. With this method we can oxidize Fe+2 (EoFe+3/Fe+2=+0.77 V), Sn+2 (EoSn+4/Sn+2=+0.2 V) and even Cl- ( EoCl2/Cl-=+1.36 V) etc.
MnO4- + 4H+ + 3e- = MnO2 + 2H2O
The standard potential is Eo=+1.69 V
MnO4- + e- = MnO42- Eo=+0.56 V.