Hello, I've been trying to write the KMno4 decomposition as a redox reaction but with no success. The reaction is:
2 KMnO4 -> K2MnO4 + MnO2 + O2
I know that Mn reduces from +7 to +5 and +4, and O oxydizes from -2 to 0. But I assume I can't just use Mn and O as standlone atoms in the half-reactions?
Anyway, here's what I was thinking the reactions should be:
O: 2O2- -> O2 + 4e-
R: MnO4- + e- -> MnO42-
R: MnO4- + 8H+ + 3e- -> Mn4+ + 4H2O
Adding it all up, I'd get:
2MnO4- + 8H+ + 2O2- -> MnO42- + Mn4+ + 4H2O + O2
Which is almost correct except for the fact that my hydrogen and oxygen ions on the left side don't cancel out with the water on the right. Where did I go wrong?