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How do electrolytes conduct electricity without redox?

  1. Jan 2, 2015 #1
    Say you have salt water. If you apply an voltage between two electrodes Na+ ions will drift towards the negative electrode and Cl- ions towards the positive electrode. If a redox reaction happens at the electrodes, the ions transfer electrons to the electrodes and current continues to flow until all the ions are reduced/oxidized. Now what happens if there are no redox reactions? Wouldn't the ions just accumulate at the electrodes, eventually screening out the potential and therefore the current would stop flowing? If thats the case how do ppl measure the conductivity of electrolytes? It seems Kohlrausch's law says current will flow even if there is no redox, how is this possible? Or is it only possible to have AC current in such situations?
     
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  3. Jan 2, 2015 #2

    Bystander

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    Just like an electrolytic capacitor.
    With AC, at a variety of frequencies, between very carefully constructed and treated electrodes, in very carefully designed and maintained cells, under threat of severe mutilation by graduate advisors.
     
  4. Jan 2, 2015 #3
    So from the previous two answers, its correct to say that DC current would not flow in an electrolyte without redox?
     
  5. Jan 2, 2015 #4

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    DC current flow in an electrolyte solution requires reduction of species at the cell cathode and/or oxidation of some other species at the cell anode. Yes.
     
  6. Jan 2, 2015 #5

    Borek

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    Please treat current in the bulk of the electrolyte separate from the charge transfer through the phase boundary.

    Imagine a long copper wire, and imagine you have access to only part of it. You can easily check if there is current flowing through the wire, not bothering about how the circuit is closed. It is not different if you observe a volume of the solution.

    In other words - you need a redox reaction to close the circuit (unless you don't*), but you don't need to see whole circuit to observe the current in the solution.

    *I wonder if it is possible for the solvated electrons to pass directly through the phase boundary, without a redox reaction. Think alkali metals dissolved in liquid ammonia.
     
  7. Jan 2, 2015 #6

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    I could not talk the organickers and p-chem faculty into cooperating on that --- department politics, turf wars. "Not gonna have a buncha fussy measurement types in my lab igniting all the solvent fumes," vs. "Not gonna have a buncha slovenly organickers making a mess in my lab and corroding all my equipment."
     
  8. Jan 2, 2015 #7

    Borek

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    I doubt is wasn't checked.
     
  9. Jan 3, 2015 #8

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    This was talk among mods?
     
  10. Jan 3, 2015 #9

    Borek

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    I mean: it would be surprising if the properties of solvated electron were not already researched and published.
     
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