Chemical Forums
Chemistry Forums for Students => Physical Chemistry Forum => Topic started by: Simon10 on December 22, 2021, 01:21:47 PM
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Hello. My name is Simon and I am new at this forum.
I have a question I can't solve after looking info on the Internet.
If I measure the conductivity of a water solution, i.e. NaCl in water, it is clear that the electrons move only outside the water (the wires, ammeter, etc.) and that inside the ones that move are the ions Na+ and Cl-. In the case of electrolysis it is easy to understand that the electrons travel through the water by a redox process: the cathode (-) realeases electrons and reduces the water and at the anode, the water is oxidized, releasing the electrons that complete the circuit. Suppose platinum electrodes.
The questions is: what happens when we measure current through a salt water solution? The voltage is not enough to produce electrolysis so there is not a redox process. Where do the electrons going up through the anode come from? Is there a kind of ionization or other non redox process in the water that transports the electrons?
Thank you very much!
Simon.
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What happens at the phase boundary can be quite complicated.
Typical conductance meter works using AC, so not only you don't have to worry about transport of the electrode reaction products (if they exist), but also even if there is no reaction current can flow through the double layer working as a capacitor on the electrode surface.