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Author: Subject: CuNO3 electrolysis?
thermiteisfun
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sad.gif posted on 1-12-2007 at 12:53
CuNO3 electrolysis?


edit: nevermind, I figured it out. Mods, please delete this post

[Edited on 1-12-2007 by thermiteisfun]




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UnintentionalChaos
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[*] posted on 1-12-2007 at 13:06


No it will not. Copper is below hydrogen on the electromotive series and will dissolve into solution in trace quantities then plate out on the other electrode. Also, using a supersaturated solution will do nothing but cause KNO3 to crystallize out if you agitate the solution (probably over the electrodes, slowing electrolysis). If you want CuNO3, I suggest you find calcium nitrate and perform a metathesis (double displacement) reaction with copper sulfate. If you can't get calcium nitrate, find ammonium nitrate and boil with a slight excess of calcium hydroxide until ammonia stops coming out of solution, bubble CO2 through the mix (or add soda water or dry ice) to precipitate any excess Ca(OH)2 as the carbonate, filter, and then perform the metathesis. You will not be able to get the anhydrous product this way though, or through any aqueous method. Also, use somewhat dilute solutions of the compounds or a lot of product will get trapped in the precipitate (coming from experience).

[Edited on 12-1-07 by UnintentionalChaos]




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bilcksneatff
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[*] posted on 1-12-2007 at 16:00


Quote:
Originally posted by UnintentionalChaos
Also, using a supersaturated solution will do nothing but cause KNO3 to crystallize out if you agitate the solution (probably over the electrodes, slowing electrolysis).
[Edited on 12-1-07 by UnintentionalChaos]


Where would the KNO3 come from? There are no potassium salts involved the electroylsis of CuNO3.
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Xenoid
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[*] posted on 1-12-2007 at 17:42


Quote:
Originally posted by bilcksneatff
Where would the KNO3 come from? There are no potassium salts involved the electroylsis of CuNO3.


The original post was deleted, he was electrolysing saturated KNO3 soln. with Cu electrodes, to try and make Cu(NO3)2.

Regards, Xenoid
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The_Davster
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[*] posted on 1-12-2007 at 18:15


The copper actually does not plate out in appreciable quantities, unless one was to keep the solution acidic. The hydroxide produced at the cathode reacts with the copper that goes into solution at the anode producing copper hydroxide(and eventually oxide, once the cell starts to restively heat itself). And if the electrolysis is carried out long enough, the nitrate is reduced to ammonia.

One theoretically could produce copper nitrate in the cathode half of a divided cell, but the huge resistance of divided cells limit the current and it would take forever to get appreciable yield.




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bilcksneatff
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[*] posted on 2-12-2007 at 08:09


Quote:
Originally posted by Xenoid

The original post was deleted, he was electrolysing saturated KNO3 soln. with Cu electrodes, to try and make Cu(NO3)2.

Regards, Xenoid


Oh!

Wouldn't electrolysing HNO3 with Cu electrodes give you Cu(NO3)2?
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12AX7
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[*] posted on 2-12-2007 at 09:54


A strong solution will dissolve it (also giving NO2); a weak solution will behave as any other acid, where copper will be dissolved and plated at the cathode until an equilibrium concentration is reached where, between mixing (at first from bubbling hydrogen, later from thermohaline convection), addition (at the anode) and removal (at the cathode), just enough is present to keep hydrogen from being produced.

If copper were reactive, like zinc, a substantial amount would dissolve from both electrodes (at a modest potential of course) at low pH.

Tim




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