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$\ce{Fe^3+}$ is reduced to $\ce{Fe^2+}$ by using

  1. $\ce{H2O2}$ in presence of $\ce{NaOH}$
  2. $\ce{Na2O2}$ in water
  3. $\ce{H2O2}$ in presence of $\ce{H2SO4}$
  4. $\ce{Na2O2}$ in presence of $\ce{H2SO4}$

I understand that options 1 and 2 are the same, and so are options 3 and 4.

But I could not find the theory - as to whether $\ce{H2O2}$ works better as a reducing agent in acidic or basic media - anywhere. It would be helpful if you can discuss the oxidising and reducing nature of $\ce{H2O2}$ in both acidic and alkaline media.

(The given answer to the question is 1 and 2)

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  • $\begingroup$ I must mention that a lot of elementary inorganic chemistry textbooks already cover this, along with several other example reactions of $\ce{H2O2}$, so I must ask you if you don't have access to such books currently, or you have and you have read them but couldn't understand what they mentioned? $\endgroup$ – Gaurang Tandon May 7 '18 at 4:13
  • $\begingroup$ I had searched for it on Google but did not find anything that clearly stated or explained whether H2O2 is a reducing or oxidising agent in acidic and alkaline media. The fact that it cannot act as both was there but not whether it is preferably OA or RA in the media. $\endgroup$ – Piyush Maheshwari May 7 '18 at 5:07
  • $\begingroup$ My book says "H2O2 acts as an OA both in acidic as well as alkaline medium." and "In presence of strong OAs, H2O2 behaves as a reducing agent in both the medium." $\endgroup$ – Piyush Maheshwari May 7 '18 at 5:12
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    $\begingroup$ Look at Frost diagram of oxygen, and also the concept of Frost diagram beforehand. A quick example is this: images.slideplayer.com/25/8148384/slides/slide_28.jpg When any species involves proton or hydroxyl ion movement in redox reactions it is clear that pH will affect the possibility or time of reducing or oxidizing in different solution conditions. $\endgroup$ – Güray Hatipoğlu May 7 '18 at 6:28
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    $\begingroup$ @Piyush Maheshwari You got it right, in acidic medium H2O2 is a quite strong oxidizing agent and only a number of chemical species, like some radicals and neutral fluorine, can oxidize H2O2. Yet in basic medium, it can even disproportionate itself. In other words, when there is a peak in Frost diagram of a species, 2 of the species react with each other, one will oxidize and one will reduce. I am unable to find Latimer diagram of oxygen, which shows the redox potentials, yet the following in comment will be for acidic medium. Always compare with redox potentials required for reactions. $\endgroup$ – Güray Hatipoğlu May 7 '18 at 15:36

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