It is said that conc. $\ce{H2SO4}$ is a strong oxidising agent. Why is it regarded as strong? In case of acids, we say something that fully ionizes in an aqueous solution is a strong acid. But what differentiates a strong oxidiser from a weak one?

  • $\begingroup$ If you want a quantitative measure of oxidizing ability, that's the redox potential. BTW, H2SO4 is a weak oxidant (though a strong acid). $\endgroup$ – Ivan Neretin Apr 26 '17 at 9:44
  • $\begingroup$ Above which value of redox potential it is regarded as strong $\endgroup$ – Paul Janson Apr 26 '17 at 9:48
  • $\begingroup$ I should have added "IMHO". There is no objective and universally accepted definition of what is weak and what is strong oxidant. As to me, HNO3 is strong. $\endgroup$ – Ivan Neretin Apr 26 '17 at 10:02
  • $\begingroup$ @Ivan what about $\ce{O2F2}$ lol? Strong would be insufficient to describe its oxidizing power. :) $\endgroup$ – Pritt Balagopal Apr 27 '17 at 11:29

Stating that a chemical is a strong oxidizing agent by itself is quite vague, and is always with respect to some other chemical. You might hear that $\ce{KMnO4}$ is a strong oxidizing agent quite commonly in organic chemistry, although thats only true while you're comparing most of the organic compounds and its reagents, like Fehlings Reagent for example. However, if you compare $\ce{O2F2}$ and $\ce{KMnO4}$, then $\ce{KMnO4}$ would seem to be a weak oxidizing agent compared to the excessive oxidative ability of $\ce{O2F2}$. You can now clearly see how oxidative strength is a relative term.

Its possible to quantify the oxidative power of a substance. Its measured as the voltage developed between the substance and reduced products when performed in aqueous medium and is called Electrode Potential. You can learn more about it over here: https://en.wikipedia.org/wiki/Electrode_potential


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