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Topic: Iodide ions with a oxidation value of 2/3?  (Read 2678 times)

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Offline Generic Username

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Iodide ions with a oxidation value of 2/3?
« on: February 21, 2016, 04:52:24 AM »
Given the following reaction, I'm struggling to see how it's possible.

ClO-(aq) + 3I-(aq) + 2H+  :rarrow: Cl-(aq) + I3-(aq) + H2O(l)

(mod edit to put text into message)
« Last Edit: February 21, 2016, 05:01:23 AM by sjb »

Offline sjb

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Re: Iodide ions with a oxidation value of -1/3?
« Reply #1 on: February 21, 2016, 05:08:08 AM »
Consider https://en.wikipedia.org/w/index.php?title=Triiodide&oldid=704463427 or similar. The oxidation state of -1/3 for the iodine atoms in your product is an average, just as e.g. in propane the oxidation state of carbon is probably formally +8/3.

Oxidation numbers are useful in some instances (like here) but less so in others.

Offline Generic Username

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Re: Iodide ions with a oxidation value of -1/3?
« Reply #2 on: February 21, 2016, 05:24:17 AM »
Consider https://en.wikipedia.org/w/index.php?title=Triiodide&oldid=704463427 or similar. The oxidation state of -1/3 for the iodine atoms in your product is an average, just as e.g. in propane the oxidation state of carbon is probably formally +8/3.

Oxidation numbers are useful in some instances (like here) but less so in others.

Hi sjb,
Then if I understand you correctly, the oxidation value of the reactant I is -3/3 which during the reaction means: (-3/3) - (-1/3) = -2/3 or an oxidation value of 2/3. The book I'm following just throws new stuff out there without any explanation, making it hard to get your head around new ideas. Thank you.

Offline AWK

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Re: Iodide ions with a oxidation value of 2/3?
« Reply #3 on: February 21, 2016, 06:09:52 AM »
2/3 is a number of electrons moved for 1 iodine atom. but I3- you have 3 atoms then number of moved electrons in reaction is 3·(2/3)=2.

Mean oxidation number for I in I3- is 1/3
AWK

Offline Generic Username

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Re: Iodide ions with a oxidation value of 2/3?
« Reply #4 on: February 21, 2016, 07:44:28 AM »
2/3 is a number of electrons moved for 1 iodine atom. but I3- you have 3 atoms then number of moved electrons in reaction is 3·(2/3)=2.

Mean oxidation number for I in I3- is 1/3
I see. Hence them multiplying by 3 later on in the working in order to match the result for Cl, which is 2. Thank you.

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