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Author: Subject: Copper acetate making iodine
99chemicals
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shocked.gif posted on 11-6-2012 at 16:28
Copper acetate making iodine


Yesterday I was experimenting with reacting a copper acetate solution with various salts and acids. I used KI for one test. When I added the KI solution to the copper acetate it immediately went went cloudy brown and then settled to make a brown solution with a white solid at the bottom which I assume is copper(ii) iodide. I added sodium thiosulfate to the mixture and it when clear. It obviously was making iodine but how?

I couldn't find any info on Copper (ii) iodide but I assume it must exist noting that there is a chloride bromide and fluoride forms of divalent copper.

Anybody know of copper acetate to be a reducing agent?

[Edited on 6-12-2012 by 99chemicals]




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UKnowNotWatUDo
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[*] posted on 11-6-2012 at 16:34


First I believe you are confusing oxidation and reduction. Reduction of iodine would be changing elemental iodine to iodide ions. Oxidation of iodide ions to elemental iodine is the reverse, which is what you are observing.

When copper(II) ions and I(-) ions are combined in solution they immediately produce unstable cupric iodide (CuI2). The CuI2 immediately decomposes into cuprous iodide (CuI) and elemental iodine (I2). The insoluble material you see settling to the bottom of your flask is most likely this cuprous iodide as it is nearly insoluble in water.

Edit: The wikipedia page on Copper(I) Iodide has more detailed information on the reaction under the preparation section.

[Edited on 6/12/2012 by UKnowNotWatUDo]
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[*] posted on 11-6-2012 at 16:58


I think that I was thinking the I- ions were positive and were lacking electrons.

I think I was comparing it to sodium or potassium reduction from solution to metallic.

Yeah I was defiantly confused thanks for correcting me.

Why does copper(ii)iodide not exist when the F, Cl, and Br all exist?




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[*] posted on 11-6-2012 at 19:16


Iodine is the lardass of the periodic system. Imagine a small theater with small seats, with people outside as the atoms. If the people are of regular size (sodium, chlorine, etc.), they'll have no trouble filling them. But if there's an obesity convention with very large people over 200 kg, they'll stuff the shit out if the theater and everyone trying to get in between will have a hard time.

Of course, the truth is much more complex. This was merely an illustrative description.




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[*] posted on 11-6-2012 at 23:22


Copper(II) iodide is unstable, because copper(II) is a sufficiently strong oxidizer to oxidize iodide ion to iodine, itself being converted to copper(I). The resulting copper(I) combines with other iodide to insoluble copper(I) iodide, which is an off-white solid.



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[*] posted on 12-6-2012 at 05:41


A nice trick for standardising thiosulphate solutions. Standard Cu2+ solution (conductor copper is good enough for a primary standard) + excess KI, titrate formed Iodine with thiosulphate, with starch indicator.



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TheAMchemistry87
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[*] posted on 12-6-2012 at 18:30


well there is such thing of copper (I) iodide this is used as a vapor of mercury checker. just check if you made iodine put it white paper for drying and it should go very messy
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[*] posted on 12-6-2012 at 22:13


Yes, you discovered what little known reaction. Copper(II) salts oxidize aqueous iodide salts to iodine. The reaction is much in part driven by the insolubility of the resulting copper(I) iodide.
2 Cu(NO3)2 + 2 NaI --> 2 CuI + 2 NaNO3 + I2
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[*] posted on 18-7-2012 at 00:30


Quote: Originally posted by AndersHoveland  
Yes, you discovered what little known reaction. Copper(II) salts oxidize aqueous iodide salts to iodine. The reaction is much in part driven by the insolubility of the resulting copper(I) iodide.
2 Cu(NO3)2 + 2 NaI --> 2 CuI + 2 NaNO3 + I2


I did the exact same reaction, except with CuSO4 and KI. the resulting mixture was cooled and filtered to get rid of the K2SO4, and the lumps of I2 + CuI were heated to sublime the pure iodine gas, wich was condensed on a cold flask. Got extremely pure iodine crystals (with a lovely crystal structure as well!). OK yields, some iodine was lost in solution.




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