metalresearcher
National Hazard
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Registered: 7-9-2010
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When is chlorate generation finished ?
Currently I am running an electrolysis of 1 Mole (60 g) NaCl to make NaClO3.
I see bubbles (H2) at the anode but barely anything at the (MMO) anode which means that oxidation indeed takes place.
It has been running for 20 hours now at constant 15A.
On a certain moment, all Cl- is oxidized to ClO3-, as the MMO anode does not support further oxidation to ClO4-.
I think that finally O2 will bubble off the anode, but in that true ?
And will the voltage increase (due to poorer conductivity ?)
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woelen
Super Administrator
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Registered: 20-8-2005
Location: Netherlands
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You indeed will see formation of O2 at the anode. and voltage goes up (provided you keep the current constant).
I myself computed the total amount of charge, passing through the cell. In a home-made cell of reasonable efficiency you can assume that for
conversion of 1 chloride ion to one chlorate ion you need 9 electrons (theoretically you can do with 6 electrons, but the reaction pathway in a
home-cell without pH-control is such that 9 electrons are needed). For ease of calculation take a ratio of 1 to 10.
If you know how many moles of NaCl (or KCl) you have in your solution, and you know the current, then you can compute how many moles per second of
electrons you are producing for the reaction (one Coulomb of charge is just a little over 0.00001 mole of electrons). With 15A current, you produce 15
Coulomb of charge every second.
Using the above computations, I had satisfactory results. You don't want to continue the process longer than needed, because at the end of the
process, when only oxygen is formed, you have much more wear of your anode.
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