I've came to know, diluted H2SO4 is used as medium in KMnO4 titration. Whereas, HNO3 is not used as it is an oxidizing agent. My question is H2SO4 is also an oxidizing agent. Then what's the problem with HNO3?

  • $\begingroup$ You need usually hot concentrated H2SO4 to manifest its oxidative properties. $\endgroup$
    – Poutnik
    Dec 19, 2022 at 15:55
  • $\begingroup$ Does diluted HNO3 show its oxidative properties? $\endgroup$ Dec 19, 2022 at 16:09
  • $\begingroup$ Does diluted HNO3 dissolve copper, while HCl does not? $\endgroup$
    – Poutnik
    Dec 19, 2022 at 16:10
  • $\begingroup$ Additionally, HNO3 is often contaminated by traces of NO2 and HNO2. $\endgroup$
    – Poutnik
    Dec 19, 2022 at 16:20
  • 1
    $\begingroup$ Cold $\ce{H2SO4}$ and $\ce{HCl}$ do not react with copper, whatever their concentration. Cold $\ce{HNO3}$ does react with copper, whatever the concentration. Of course, the reaction rate depends on the $\ce{HNO3}$ concentration. It decreases at low values of concentration $\ce{[HNO3]}$. So $\ce{HNO3}$ is an oxidizing agent, and not cold $\ce{H2SO4}$ $\endgroup$
    – Maurice
    Dec 19, 2022 at 16:53

1 Answer 1


It depends on the use and exact reaction. Different oxidizers have different potentials [strengths] and react by different mechanisms and cause different reactions. If the oxidizing properties of permanganate and the reducing properties of the other reactants are paramount it is imperative that no other oxidants or reductants are present. In the analytical use of permanganate, a strong oxidizer like nitric acid would interfere, atmospheric O2 might interfere, Cl-, Br-, I- HS-would be oxidized. Complete reduction of permanganate to manganous ion requires an excess of Hydronium ion. The only common acids that supply H3O+ and have low oxidation potentials and cannot be oxidized are sulfuric and possibly phosphoric and some sulfonic acids; so that is what is used.


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