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I have seen both potassium permanganate and the permanganate ion being called the oxidizing agent. Isn't it more appropriate, however, to call the permanganate ion the oxidizing agent only as the potassium ion doesn't play any role in oxidizing?

Similarly, is potassium dichromate an oxidizing agent or is the dichromate ion the oxidizing agent?

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    $\begingroup$ It may be more precise to specify that it's the permanganate ion, but it's not wrong to say that KMnO4 is an oxidising agent. At the end of the day, I don't think anybody cares enough about it to make this distinction. You can't have permanganate without a counterion anyway. $\endgroup$
    – orthocresol
    May 10 at 13:04
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    $\begingroup$ Permanganate with any counterion is an oxidising agent as it is the manganese that is the active agent. Similarly with dichromate. $\endgroup$
    – Waylander
    May 10 at 13:24
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    $\begingroup$ In context of substances, KMnO4 and not MnO4^- is the oxidizing agent. In context of ions, MnO4^- and not KMnO4 is the oxidizing agent. So, choose the context. The same for chromium. $\endgroup$
    – Poutnik
    May 10 at 13:51
  • $\begingroup$ @orthocresol I just realized that one might argue further that not MnO4-, but rather Mn is the oxidizing agent. $\endgroup$ May 10 at 13:55
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    $\begingroup$ P.S.: ... and there is the 3rd context of elements changing oxidation number, where the respective element is the oxidizing agent. $\endgroup$
    – Poutnik
    May 10 at 14:01

1 Answer 1

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  • In the context of substances, $\ce{KMnO4}$ and not $\ce{MnO4-}$ is the oxidizing agent.
  • In the context of ions, $\ce{MnO4-}$ and not $\ce{KMnO4}$ is the oxidizing agent.
  • In the context of elements changing their oxidation number, $\ce{Mn^{VII}}$ is the oxidizing agent.

So, choose the context.

The same respective contexts are there for the dichromate case.

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