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How do ions move in an electrolytic cell?

  1. Oct 16, 2008 #1
    Hello

    I'm wondering if someone can explain how OH- ions physically move from the anode to the cathode within an electrolytic cell (w/ pure water) .

    Do they physically migrate from one side to the other? Or do they just pass electrons/protons back and forth between other ions H3O+ to the other side?

    Thanks
     
  2. jcsd
  3. Oct 16, 2008 #2

    Borek

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    Staff: Mentor

    Both.

    H+ and OH- conductivity is much higher than that of other ions of smilar size and charge. That's because protons jump between water molecules free electron pairs:

    Code (Text):

    H-O-H[sup]+[/sup]  O-H          H-O   [sup]+[/sup]H-O-H
      |     |      ->      |      |
      H     H              H      H
    Similar process works for OH-m aking charge transfer through the solution much faster.

    Sorry about ASCII graphics, but it is 0:30 am here and I am spent.
     
  4. Oct 16, 2008 #3
    I'm not a chemistry fellow, but I am a electronics engineer tech fellow.
    I'd say that with water and gasses.....instead of JUST having free electrons flowing... You have atoms that are capable of flowing since they're not bonded together. As i'm sure you know that atoms naturally seek to be neutral. An Ion is a positively charged or negatively charged atom. This happens through losing a electron or gaining an electron. Now.... if you put a potential energy source to the applied cell. You'll have electrons leaving atoms and joining with other atoms. Leaving atoms ionized. These ionized atoms unlike in copper atoms can flow since they're not stuck together so they will flow to whatever different potential. Positive ions will flow to negative potential, and Negative ions will flow to positive potential.
    That's the difference between current through gasses and liquids vs current through solids like copper.
    And the AMPS will be measured like this Q/T
    Charge per second.

    I hope this helps in anyway... since i'm not a chemist I don't know if i've answered your question or not.
     
  5. Oct 16, 2008 #4

    Borek

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    Staff: Mentor

    No. In general in the solution that is able to conduct electricity you don't have just atoms, that will get ionized. You already have ions, that are stable in this charged form.
     
  6. Oct 16, 2008 #5
    Stable in a charged form?

    I've never heard of atoms being stable while being positive/negatively charged. Unless they're in an ionic bond in which they're balanced due to the positively charged ion bonded to the negatively charged ion. But as far as free ions I wouldn't know about that.

    If you're right though i'd love to learn more about this.
     
  7. Oct 16, 2008 #6

    Borek

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    Staff: Mentor

    Yes. They are stabilized by water molecules dipoles. Look for solvation.
     
  8. Oct 16, 2008 #7
    Ok that's what I suspected....They're being stabilized by essentially an ionic bond with different charges.

    I thought you were saying they were stable completely by themselves.
     
  9. Oct 16, 2008 #8
    Does this occur often during electrolysis:

    H2O H2O + voltage => H3O+ OH-

    Where a proton moves to the right toward the anode.
    And electron moves left toward the cathode.
     
    Last edited: Oct 17, 2008
  10. Oct 17, 2008 #9

    Borek

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    Staff: Mentor

    I think I know what you mean, but this is not an ionic bond. Water molecules are dipoles, but they are not charged.

    Besides, in the case of large, multiatomic ions, solvation plays very small role. You may treat them as stable by themselves.

    This world is governed by its own laws. They don't contradict physics as you know it, but - especially on micro scale - they are in many aspects completely different from the solid state ones. Charge transfer between atoms/ions means chemical reaction, and to proceed these require that some conditions are meet.
     
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