Sacrificial Anodes and Oxidation Number of KMnO4

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Discussion Overview

The discussion revolves around two main topics: the effectiveness of zinc as a sacrificial anode in preventing the corrosion of iron and the determination of oxidation states in potassium permanganate (KMnO4). The scope includes conceptual understanding and technical reasoning related to electrochemistry and oxidation states.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant questions whether it is correct to say that corrosion does not occur in an iron nail wrapped with zinc, noting that zinc is more reactive and will oxidize preferentially, but also expressing uncertainty about whether some iron may still oxidize.
  • Another participant discusses the oxidation states in KMnO4, stating that potassium is +1 and oxygen is -2, while expressing uncertainty about the oxidation state of manganese and suggesting that it is +7.
  • A later reply acknowledges that while the participant's assumptions about oxidation states are generally correct, there are exceptions where oxygen may not have an oxidation state of -2, and emphasizes that oxidation numbers are merely an accounting tool.

Areas of Agreement / Disagreement

Participants express varying levels of certainty regarding the oxidation states and the corrosion process, with no consensus reached on the absolute correctness of the claims made. Multiple viewpoints on the oxidation states and the implications of using zinc as a sacrificial anode remain present.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about oxidation states and the conditions under which certain oxidation states apply. The discussion does not resolve the complexities of oxidation states in different environments or the complete effectiveness of zinc in preventing corrosion.

Procrastinate
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1. I have a question regarding an iron nail wrapped with zinc. The question asks me "Is it correct to say that corrosion did not take place in the nail wrapped with zinc? Explain."

I am not sure whether this is correct but I know that that zinc is more reactive than iron and will thus be more likely to oxidise than iron. However, as it is more likely, there will be some iron which will oxidise since not all of the iron has been cloaked by the zinc.
Is this correct and best explanation? I am not absolutely sure.
----------------------

2. KMnO4. O = -2 but how would I figure out what K and Mn is then? Apparently K is +1 and Mn is +7 but I don't know why. Could anyone please explain? I know they have to add up to zero.
 
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Procrastinate said:
KMnO4. O = -2 but how would I figure out what K and Mn is then? Apparently K is +1 and Mn is +7 but I don't know why. Could anyone please explain? I know they have to add up to zero.

Manganate has variable oxidation states, and it's dependent on the environment it's in. Potassium, as you said, has an oxidation state of +1; which I assume you are just expected to know. I again assume the same applies to Oxygen, its oxidation state is invariably -2. From these constants, you can deduce the oxidation state of Manganate.

Discalimer: I can not be held accountable for the accuracy of this post. Someone more knowledgeable will hopefully verify, or correct, as appropriate.:wink:
 
nobahar said:
I can not be held accountable for the accuracy of this post. Someone more knowledgeable will hopefully verify, or correct, as appropriate.:wink:

You are in general right, although in some compounds oxygen is not -2. But as a first approximation -2 is OK.

More on oxidation numbers calculation.

Please note that oxidation numbers are just an accounting device, they don't reflect any measurable property of atoms.

--
 
Borek said:
You are in general right, although in some compounds oxygen is not -2. But as a first approximation -2 is OK.
Thanks Borek.
 

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