I have been performing titrations of a known concentration of hydrogen peroxide using 0.01N potassium permanganate and consistently requiring more potassium permanganate than what is estimated to reach the end point. I have already performed standardization titrations of the potassium permanganate with sodium oxalate and the results show that the concentration of the potassium permanganate is accurate/as described. Any other suggestions as to why this may be happening? It's as if the concentration of the hydrogen peroxide is stronger than described by the manufacturer, but I know this is highly unlikely. If anything, the concentration would be lower due to decomposition.
(For context, I am using a known concentration of hydrogen peroxide (100 uL of 3% H2O2) to ensure that the procedure is working correctly before moving on to applying it to my experiments)
Hello, the %3 H2O2 is a pre-diluted solution (in DI water), and I am adding to a DI water and H2SO4 solution.
1. Make sure that the solution with the hydrogen peroxide is very acidic, that way you reduce MnO4- all the way to Mn2+. If the solution is not acidic enough, you reduce MnO4- to MnO2, and then you would need more MnO4-. How acidic must be mentioned in the description of your assay, otherwise look it up, I forgot.
2. After the first addition of MnO4-, wait. You may notice that the purple colour disappears slowly. Kind of contrary to point 1, you need a tiny bit of MnO2 to catalyse the reaction, so I was told.
Good luck!
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