I came across a question :

Which of the following compound does not decolourise an acidified solution of $\ce{KMnO4}$?

Answer was:


After doing a bit of research I found that $\ce{KMnO4}$ oxidises $\ce{HCl}$ to $\ce{Cl2}$. I doubt whether $\ce{KMnO4}$ would also oxidise chloride ions in case of acidified solution of $\ce{FeCl3}$.

I know that the ferric ion cannot be oxidised further.

  • 2
    $\begingroup$ Are you sure that "[you] know iron cannot be oxidised further"? Ferrate (IV), Ferrate (V) and Ferrate (VI) oxidation states exist even though the (VI) is the most encountered among the three. $FeCl_3$ has iron (III). $\endgroup$
    – Kav
    Commented May 4, 2021 at 13:25
  • $\begingroup$ Have you considered ferric chlorocomplexes ? $\endgroup$
    – Poutnik
    Commented May 4, 2021 at 13:27
  • $\begingroup$ @Kav how likely is it that $\ce{Fe(III)}$ can be oxidized further ? Will it do under normal conditions with $\ce{KMnO4}$ or do you require drastic conditions ? $\endgroup$
    – Ashish
    Commented May 4, 2021 at 13:31
  • 3
    $\begingroup$ Iron can be oxidized further, but not by KMnO4. $\endgroup$ Commented May 4, 2021 at 13:36
  • 1
    $\begingroup$ @Kav Well, ferrates are stronger oxidants than permanganates, and other higher oxidation states of Fe don't exist in water. $\endgroup$ Commented May 4, 2021 at 15:06


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