Help with galvanic cells

  1. What I know about galvanic cells is : zinc is the anode and copper is the cathode, zinc loses electrons and it turns into ions leaving its electrons on the electrode. While copper is the cathode it also loses electrons and turns into ions leaving its electrons on the electrode, but zinc has more tendency to form ions than copper
    So the anode (zinc) becomes negatively charged with respect to the cathode, consequently electrons move from the anode to the cathode on connecting a conducting wire,
    I don't understand why the atoms of the
    Electrode are ionized in the first place and why are they placed in a solution of their own salts ???

    Zinc and copper is just an example, I know that it can be other elements
     
    Last edited: Apr 11, 2014
  2. jcsd
  3. Borek

    Staff: Mentor

    I don't understand it either.

    You sure don't mean elements?
     

  4. It is a fast typing mistake I edited it
     
  5. Borek

    Staff: Mentor

    I think you are putting horse behind teh cart.

    We can explain why these reactions occur using energy considerations, ΔG=ΔH-TΔS, whatever, but it will only make things more complicated to understand at this stage.

    Why don't you accept for now that we experimentally checked they react, and we are trying to explain observed phenomena?
     
    Last edited: Apr 13, 2014

  6. I'm not asking for a complicated explanation!
     
  7. Borek

    Staff: Mentor

    What is complicated in the fact we observed them to react?
     
  8. The observation is simple, and any scientific observation is so simple, I want to know the scientific explanation
     
  9. Why is zinc ionized ??????
     
  10. Astronuc

    Staff: Mentor

    See http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/echemcon.html

    http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/electrochem.html

    http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/electrolyt.html

    Galvanic cells are based on electrochemical processes, namely oxidation and reduction reactions.

    Please review these
    http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/redoxcon.html


    The different elements have different affinities for electrons and different ionization potentials, which is just inherent in Nature. If one looks at the galvanic series, one notes that some elements preferentially attract electrons, while others preferentially lose electrons.

    http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/electrochem.html#c3
     

  11. I really appreciate your effort, but I still can't understand why both electrodes are ionized when they are placed in their own solutions
     
  12. Borek

    Staff: Mentor

    What does it mean "ionized electrode"?
     

  13. I mean some atoms of them get ionized

    Some atoms begin to lose electrons and turn to ions, why does that happen when the electrode is placed in its solution
     
  14. Borek

    Staff: Mentor

    Because that's required for the thermodynamical equilibrium.

    As I wrote earlier - it can be explained using thermodynamics, or energy considerations, but I doubt it would be helpful, as it requires understanding things that you most likely have not heard of yet - so you will get just more confused. IMHO at this stage it is easier and better to just accept that's the way it is.
     

  15. I'll accept for now that this happens to reach thermodynamical equilibrium, so this happens when ever an element is placed in its own solution ??
     
  16. Borek

    Staff: Mentor

    In a way. It is most obvious for metals, for other elements chemistry is much more difficult to follow, as they don't necessarily create simple ions that could get into water - but yes, in general every element put into water will somehow get "ionized" and charged in the process.
     

  17. So when a zinc electrode is dipped in a ZnSO4 electrolyte solution, some zinc atoms begin to get ionized, turning into positive ions and their electrons stay on the electrode, that's it? Don't the zinc ions or the electrons get involved in any reaction after that before connecting a wire between the electrodes ??
     
  18. Borek

    Staff: Mentor

    No, there is no further reactions before the current starts to flow.

    That is, they can't be ruled out, for example when the solution is acidic enough to dissolve the Zn. But we assume solution was prepared in such a way side processes don't interfere.
     

  19. Do the zinc ions form bonds with the negative oxygen atoms of water or does it form Zn(OH)2 with the free hydroxide negative ions?
     
  20. This is apropos of nothing, and I am FAR from the point where I'd argue with Borek about anything chemistry related. However, folks had a bit of a contre-temps over at Wikipedia when the terms "anode" and "cathode" got used in the lead-acid cell entry, and I thought I'd chime in:

    The very terms anode and cathode are a little misleading when it comes to batteries, since it matters which side of the cell wall you're on. The "source" of electrons for the inside of the cell, is the sink for electrons outside of the cell. I tended to use the terms positive/negative + plate/electrode just to keep things clear.

    Lastly, ElmorshedyDr: There's a pretty good wikipedia entry on the LeClanche Cell which has reactions akin to what you're discussing. Unless it directly contradicts Borek, maybe reading it would give a different perspective.

    Yours in service,
     
  21. Borek

    Staff: Mentor

    It is about freely floating Zn2+. For sure they are in the form of aqua complex, every cation in the solution is at least hydrated.
     
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