[sodium.dioxid]

I have always failed to understand why galvanic cells work (why the redox reaction takes place) ; I am intuitively inclined to think that nothing should happen when the switch is turned on. Let me explain. The zinc half cell is overall neutral and the copper half cell is also neutral overall. There is no difference in charge; everything is in a state of neutrality. If the copper cell was more positively charged than the zinc half cell, then I could understand why the electrons move from the zinc half cell to the copper half cell. But this is not case as both cells are neutral. So the movement of electrons doesn't make any sense. If it is not a difference in charge that is driving the movement of electrons, then what is driving it?

[Hunter2]

You forgot he Hydrogen. In a aqueous solution zinc has the tendency to dissolve. It is shown on the redox potential -0,76 V. Copper is more like to plate +0,34 V.

If the circuit is closed then Zinc will dissolve and Electrons will remain on the cathode. These electrons travel to the anode and pic copper ions.

[sodium.dioxid]

Sorry, I didn't make myself clear. The issue is not that I don't believe the electrons move; the issue is I am having trouble understanding why this happens (what drives the reaction). But can you please tell me this. Would it be correct to say the copper ions exert their greater-than-zinc electron-attraction influence all the way on the other half cell and thus driving the reaction?

[Arkcon]

No.  Two electrodes, each in a half cell, produce no reaction.  The electrons are in motion within the metal bars themselves.  However, when the two electrodes are connected by a conductor, the electromotive force does move electrons from one metal bar to another -- there is sufficient force for use to make these electrons in the conductor do work -- light a flashlight bulb, run a motor, drive another battery in reverse to plate metal, etc.

[sodium.dioxid]

No.  Two electrodes, each in a half cell, produce no reaction.  The electrons are in motion within the metal bars themselves.  However, when the two electrodes are connected by a conductor, the electromotive force does move electrons from one metal bar to another -- there is sufficient force for use to make these electrons in the conductor do work -- light a flashlight bulb, run a motor, drive another battery in reverse to plate metal, etc.

Zinc releasing its electrons and dropping into the solution as ions is indeed a reaction (initiated by the completion of the circuit). Am I missing something?

[Borek]

When you put any piece of metal into solution it immediately starts to react - but the reaction doesn't go far, just till the metal is charged to the equilibrium potential (different for each metal). It can mean just a few electrons (or just a few ions released), or even fraction of an ion (which doesn't make much sense in a static environment, but when you take kinetics into account it can just mean an atom being reduced/oxidized and oscillating between metal surface and solution; or something equivalent). If these electrons have no place to go, nothing changes further. If you connect this piece of metal to another one, charged differently (so having a different potential), current starts to flow which can mean making "place" for a further reaction.

[sodium.dioxid]

When you put any piece of metal into solution it immediately starts to react - but the reaction doesn't go far, just till the metal is charged to the equilibrium potential (different for each metal). It can mean just a few electrons (or just a few ions released), or even fraction of an ion (which doesn't make much sense in a static environment, but when you take kinetics into account it can just mean an atom being reduced/oxidized and oscillating between metal surface and solution; or something equivalent). If these electrons have no place to go, nothing changes further. If you connect this piece of metal to another one, charged differently (so having a different potential), current starts to flow which can mean making "place" for a further reaction.

Wow. I never thought of a metal in solution as an equilibrium process. Chemical equilibrium is far more prevalent than I though. Thank you for this insight. Can you please help me understand further by explaining what exactly you mean when you say the other metal is "charged differently" and has a different potential? It is not immediately clear to me in what way.

[Borek]

Please reread the first phrase. For each metal how far the reaction goes is something that is specific for this particular metal (and for obvious reasons must be a function of standard oxidation potential for the metal).

You can also think about it this way - when the concentration of ions in the solution is zero, potential (as described by the Nernst equation) is undefined (or infinite, if you assume ln(0) = -∞). It can't stay this way, something has to happen. So the metal will dissolve, till the Nernst equation makes some sense. If there are ions going into solution, electrons must be left on the metal - and it gets charged. When it gets charged - and it gets charged differently than other objects in the vicinity - it gets a potential. This potential can be very tiny, but it is already there before you connect the electrodes.

[sodium.dioxid]

If there are ions going into solution, electrons must be left on the metal - and it gets charged. When it gets charged - and it gets charged differently than other objects in the vicinity - it gets a potential. This potential can be very tiny, but it is already there before you connect the electrodes.

THIS is golden. I learned so much it feels like I cheated. If only textbooks could explain it this way and stopped leaving out conceptual information. Thank you so much!

[jdonpugh]

No.  Two electrodes, each in a half cell, produce no reaction.  The electrons are in motion within the metal bars themselves.  However, when the two electrodes are connected by a conductor, the electromotive force does move electrons from one metal bar to another -- there is sufficient force for use to make these electrons in the conductor do work -- light a flashlight bulb, run a motor, drive another battery in reverse to plate metal, etc.

I think two electrodes in a vacuum two from a different place can produce light like flashlight if they are different in nature.

[Borek]

I think two electrodes in a vacuum two from a different place can produce light like flashlight if they are different in nature.

Sorry to say that, but you are not making any sense.