Ash96
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electrolysis of water
i did electrolysis today
the electrolyte is water with a little salt
using copper electrode
i let it run for a few minutes and the whole thing change colour
my question is what is that?
is that copper oxide?
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Urzah
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Maybe copper Hydroxide Cu(OH)2.
If you filtrate and dry it it should be green if its copper hydroxide.
If its Cu2O copper oxide (I doubt) it will be reddish colour when dried.
For the electrolysis of water, you should use a platinum electrode. I think a stainless electrode should do it (but not sure, never tested it).
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elementcollector1
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It's not copper hydroxide, because freshly prepared Cu(OH)2 is blue in color. If anything, it looks like either iron hydroxide or copper metal, or
perhaps a brown copper oxide.
Why do your electrodes look so gray and un-coppery?
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Ash96
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Quote: Originally posted by Urzah  | Maybe copper Hydroxide Cu(OH)2.
If you filtrate and dry it it should be green if its copper hydroxide.
If its Cu2O copper oxide (I doubt) it will be reddish colour when dried.
For the electrolysis of water, you should use a platinum electrode. I think a stainless electrode should do it (but not sure, never tested it).
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i wanted to make some copper oxide
when i take out the wires and dry it , the anode is green
[Edited on 16-11-2012 by Ash96]
[Edited on 16-11-2012 by Ash96]
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Ash96
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| Quote: Originally posted by elementcollector1 | It's not copper hydroxide, because freshly prepared Cu(OH)2 is blue in color. If anything, it looks like either iron hydroxide or copper metal, or
perhaps a brown copper oxide.
Why do your electrodes look so gray and un-coppery? |
its copper wire
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Urzah
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Which copper oxide you want? CuO or Cu2O?
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Ash96
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CuO
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Urzah
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Do you have access to more chemicals? i think the best way to get CuO is by the heating of Cu(OH)2, which can be obtained by precipitation of Cu2+
with NaOH...
Will try to find my ref if you want it. Should have it somewhere.
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elementcollector1
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How about this: Run your electrolysis with a higher salt concentration, or better yet a strong mineral acid in there (make sure to do this outside
with good ventilation!), then precipitate out Cu(OH)2 with some NaOH (this should be bright blue). Let this dry, and in air it should turn to dry CuO.
Remember, the electrolysis of more concentrated brine produces chlorine gas, which is deadly when inside (and even when outside in some situations).
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Ash96
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no i dont have access to many chemicals
that's why i have to make them
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elementcollector1
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Gotcha. I was in that position myself once...
Anyway, new plan: Split up the electrolysis into two containers. One has one electrode, the other the other electrode. Place concentrated salt water
in both containers and soak a piece of tissue paper, paper towel, or similar substance in the saltwater, and position this so that the paper towel
dips into the water in both containers.
Now apply electric current. The solution with the positive electrode should turn blue (copper chloride in solution) and give off a smell of chlorine,
while the negative electrode should bubble noticeably (while not producing any precipitate).
When you feel the cell with the positive electrode cannot get any more blue (saturated solution), turn off the electricity, remove the paper towel and
electrodes.
Now, if all has gone well, you've made a solution of dilute NaOH at the negative electrode (should be clear) and a solution of concentrated CuCl2 at
the positive electrode (should be a vivid blue). Now, add the clear solution to the blue solution (if there are any precipitates before this, filter
them off and keep them) and you should immediately see a blue precipitate; that's your finished copper hydroxide. Again, filter this out with a coffee
filter or paper towel and leave to dry in open air; it should turn to your desired CuO.
So, all in all, you'll need:
-Copper electrodes
-Saturated salt water
-Paper towels
-Two glass or plastic containers
-Electricity (preferably fairly high amperage, a 6V battery or 9V battery will work for short runs, do NOT use house current at any time)
The reason your copper anode turned green is the formation of CuCl2 on the surface, which often turns green for some reason (Acidic copper chloride?).
This is a procedure that can be done easily with household stuff, but still, and I cannot stress this enough: DO NOT do this stuff inside. Chlorine
can build up, and anything over pool chlorine levels can leave you gasping for air.
Hydrogen is also dangerous near open flames.
I hope to see your CuO!
-EC1
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Ash96
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thanks but where do i put the paper towel ?
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elementcollector1
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If you're talking about the small strip of paper towel that acts as a salt bridge, it 'connects' the two containers: One end is dipped in one
container's solution, and the other end is dipped in the other container's solution. This allows for transfer of ions, but not electrons.
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Ash96
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okay i got it ...thanks a lot
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ElectroWin
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copper(I) oxide is brown; copper oxide (II) is black; copper (II) carbonate is green; copper (II) hydroxide is more a light blue-to blue-green.
the colour of copper salts changes according to pH. in acids, it's more green, in bases, it's more blue. this green stuff coats the anode, which is
more acidic. so you could be looking at copper(II) chloride or carbonate.
i was successful making a lot of CuO by treating native copper with hot conc H2SO4.
you can probably do this with electrolysis by using dilute H2SO4 as the electrolyte. you may get any of CuO, Cu(OH)2, and CuSO4 as result. the CuO and
Cu(OH)2 are soluble in dilute acids, but if you run the cell until the blue solution clears then it should all precipitate.
oh, do note that you get SO2 gas from the anode as this process runs.
[Edited on 2012-11-17 by ElectroWin]
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