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I know iron can react with many solutions, but when I tried to mix iron powder together with permanganate or dilute sulphuric acid, the iron powder would not react and instead, it just float on the surface of the solution. I tried to stir it for several minutes but it seems doesn't work.

It is pure iron powder, can be attracted by magnet

How can I dissolve iron powder and let it become $\ce{Fe^2+}$ or $\ce{Fe^3+}$ ? (Just dissolve it is ok)

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    $\begingroup$ To float on the surface of a water solution (density slightly above 1) is quite a peculiar thing to do for iron (density 7.8). Isn't the powder stained with some kind of oil, by any chance? $\endgroup$ – Ivan Neretin Apr 27 '16 at 17:44
  • $\begingroup$ @IvanNeretin I've seen iron filings do this, and stirring (with a magnetic stir bar, at least) isn't exactly the best way to break surface tension at the top of water. $\endgroup$ – SendersReagent Apr 27 '16 at 19:28
  • $\begingroup$ Then we have to lower the surface tension. I think a little drop of acetone might help. $\endgroup$ – Ivan Neretin Apr 27 '16 at 19:33
  • $\begingroup$ As far as the question goes, I don't think you're going to get it to dissolve without making $\ce{Fe^{2+}}$ or $\ce{Fe^{3+}}$. There may be some wierdo $\ce{Fe^0}$ complexes that would do it, but those would be the exception. I'm not even sure it would work at all. $\endgroup$ – SendersReagent Apr 27 '16 at 19:44
  • $\begingroup$ what is the iron powder made of? just pure elemental iron in its various oxidation states? I don't know how iron bonds so I'm not sure if it exists elemental or not :/, but if I can get a little bit of information about this I think I can help with the dissolving problem $\endgroup$ – Ryan Apr 27 '16 at 20:19
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I did some brief research and I saw that sulfuric acid can dissolve iron:

Fe(s) + H$_2$SO$_4$(aq) → Fe$^{2+}$(aq) + SO$_4$$^{2-}$(aq) + H$_2$(g)

Of course, this would leave sulfate ions and perhaps some precautions would need to be taken because of hydrogen gas production. If you absolutely cant have any sulfate ions, you could precipitate them out by adding barium or silver ions to the solution, but that would require extra work and introduce new ions to the solution. Also note, the iron ions should be aqueous in +2 state but I read that if there is oxygen in the system (which there naturally would be), some iron(II) can oxidize to iron(III).

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  • $\begingroup$ dissolution of iron in diluted acid is painfully slow. $\endgroup$ – permeakra Apr 27 '16 at 21:38

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