CoolFool
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Electrolysis of water
I wanted to show my sister how electrolysis of water works and so i filled a beaker with water and adder salt . I passed a current of 3 v . Some gas
was produced but to my surprise there was also formation of a brown precipitate. I checked the salt and found out that it also contained Potassium
Iodide . I carried it out again but the result was the same. Can someone tell me
the cause for this?
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violet sin
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What are your electrodes made from? Could be corrosion
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elementcollector1
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If your electrodes are steel or iron, that's almost definitely iron(III) hydroxide.
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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CoolFool
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No I was using copper wires
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crystal grower
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Then probably copper(I) oxide. Potassium iodide is harmless in this experiment and on top of that, its content in table salt is negligable.
Try stainless steel instead, or maybe carbon rods.
[Edited on 4-11-2016 by crystal grower]
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woelen
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At the anode you get impure copper(I) oxide. This stuff is yellow/brown.
At the cathode you get hydrogen gas.
If you use carbon rods (e.g. from spent zinc batteries), then you get chlorine at the anode, and you can easily smell it. That would be a more
understandable demo for your sister.
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Texium
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Thread Moved
4-11-2016 at 08:53 |
Sulaiman
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also, use sodium bicarbonate for the electrolyte as oxygen is slightly more electronegative than chlorine,
so elevtrolysis of sodium chloride solution produces H2 and Cl2 and NaOH in solution.
Most of the chlorine will combine with the NaOH but some escapes.
It just makes the explanation of the results easier using bicarbonate.
CAUTION : Hobby Chemist, not Professional or even Amateur
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Matthew
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You might try getting the graphite out of the pencil. Don't heat up the rods too much though or they will break
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Liamatpm
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You could also get a 6v battery and you'd get 4 carbon electrodes. Also I'd recommend using a high wattage. Remember P=I*E,
P-power in watts
I- ohms
E-Volts
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MrHomeScientist
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To simplify the explanation, a baking soda solution using distilled water and using graphite electrodes would be best. That way you get oxygen and
hydrogen, and no complications from reactions with the electrolyte or electrodes.
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WGTR
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Interestingly enough, I just found out that mild, low carbon steel is an excellent low-cost anode for water electrolysis. This is provided that the
Na2CO3 electrolyte is very pure, i.e., no halogen contamination. Just a few ppm of added NaCl is
enough to induce corrosion of the steel anode. With high enough electrolyte purity, however, I've used 1018 steel anodes in a cell for days with
little more than a slight color change from a transparent oxide layer. No coloring of the solution was noted, and no loose corrosion products were
present.
[Edited on 12-20-2016 by WGTR]
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Jstuyfzand
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Quote: Originally posted by WGTR  | | Interestingly enough, I just found out that mild, low carbon steel is an excellent low-cost anode for water electrolysis. This is provided that the
Na2CO3 electrolyte is very pure, i.e., no halogen contamination. Just a few ppm of NaCl is enough to induce corrosion of the
steel anode. With high enough electrolyte purity, however, I've used 1018 steel anodes in a cell for days with little more than a slight color change
from a transparent oxide layer. No coloring of the solution was noted, and no loose corrosion products were present. |
Wouldn't NaOH make for an even better electrolyte? No possible Co2 evolution, ofcourse provided it is pure.
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WGTR
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KOH also seemed to work, although that transparent oxide layer formed more quickly. It does seem to be less pure that the
Na2CO3, however. Here's what I used:
 
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CoolFool
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I tried doing the same experiment with all the same stuff but this time i got a green precipitate . Is it copper hydroxide? also the current was 4.5V
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Liamatpm
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It was probably Iron hydroxide. (Like what other people have said) I figured to say what I thought because with more information the better.
[Edited on 22-3-2017 by Liamatpm]
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Liamatpm
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| Quote: Originally posted by CoolFool | | I tried doing the same experiment with all the same stuff but this time i got a green precipitate . Is it copper hydroxide? also the current was 4.5V
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It was the copper like you said.
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