Does hydrogen peroxide on oxidation gives oxygen gas only in basic medium?

I thought that was true but I read about these reaction of $\ce{H2O2}$ in acidic medium: $$\ce{2MnO4- + 6H+ + 5H2O2 -> 2Mn^{+2} + 8H2O + 5O2}$$

$$\ce{K2Cr2O7 + 4H2SO4 + 3H2O2 -> K2SO4 + Cr2(SO4)3 + 7H2O + 3O2}$$

What is the possible explanation of both the title and the reactions?

  • $\begingroup$ I don't get it, what would expect when H2O2 is oxidized? $\endgroup$ – Mithoron Oct 8 '18 at 16:32

In both reactions $\ce{H2O2}$ is oxidized by the more powerfull oxidizers permanganate ($\ce{KMnO4-}$) and dichromate ($\ce{Cr2O7^2-}$).

Whether or not oxygen is produced depends on the actual reaction and not necessarily on pH. A rule is that when hydrogen peroxide is oxidized by a stronger oxidant, free oxygen is produced. It is not always the case when hydrogen peroxide is the oxidizing agent itself.

See this discussion: Half equations for $\ce{H2O2}$


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