Can concentrated (18 M) $\ce{H2SO4}$ oxidize $\ce{Fe^2+}$ to $\ce{Fe^3+}?$ Or does it actually block the oxidation? I read in some forum somewhere that in order to prevent $\ce{Fe^2+}$ from being oxidized, one should acidify the solution. I don't know if that's the reason why we added $\ce{H2SO4}$ in our $\ce{Fe^2+}$ solution. But then again, isn't iron(II) unstable in the presence of acid and water? And will it oxidize?

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    $\begingroup$ Welcome to our site! Please note that Chemistry.SE is a formal place and informal language is usually frowned on, especially the use of expletives. $\endgroup$ Sep 24 '19 at 17:11
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    $\begingroup$ Please control your language. It does not contribute anything. There are good teachers and bad teachers in the whole world. $\endgroup$
    – M. Farooq
    Sep 24 '19 at 17:12
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    $\begingroup$ @M.Farooq Complete edits are appreciated better! $\endgroup$ Sep 24 '19 at 17:15
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    $\begingroup$ @M.Farooq I'm really sorry I'm new to this site I'll mind my wordings next time thank you so much for pointing that out $\endgroup$
    – Mochi
    Sep 25 '19 at 8:50
  • $\begingroup$ Which reaction are you talking about, i.e. what is the oxidation agent? Sulfuric acid is usually not classified as oxidizing acid (nitric acid, in contrast, is). $\endgroup$ Sep 28 '19 at 18:57

The explanation given to you is rather incorrect. Dilute sulfuric acid is added to iron(II) or even iron(III) salts is added to prevent hydrolysis of the salts. What happens when you don't add an acid to iron(II) solution in water. With time, you will see that a brown precipitate is forming and settling to the bottom. Iron forms hydroxides which are very quickly oxidized by dissolved oxygen (not by dilute acid) to a brown rust colored product.

As a result, the concentration is no longer the correct concentration. The same job can be done adding a small amount of HCl so there is nothing special about sulfuric acid. Chloride salts are even more prone to hydrolysis that's why iron(II) chloride or iron(III) chloride are never used for solution preparation.


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