Voltaic Cell behaviour as described in this video

[cianfa72]

TL;DR

Voltaic cell behavior with no external connection

Hi,

googling for Voltaic cell I found this video about it. At minute 2:35 to 2:54 you can see that, without any electrical conductor connected between electrodes, in the Copper half-cell the metal electrode (Cathode) gets an amount of negative charges (electrons). Basically what described there is that Copper atoms oxidize passing in solution as Cu++ cations loosing electrons inside the Copper electrode.

As far as I Know actually, at least when an external connection is in place, the opposite reaction (Copper ions reduction) should take place at the Cathode electrode.

Do you think that video is correct ? Thanks.

 

[Borek]

If there are no copper ions on the solution, can they get reduced? Or are the options of in which direction reaction can proceed limited?

 

[cianfa72]

If there are no copper ions on the solution, can they get reduced? Or are the options of in which direction reaction can proceed limited?

As explained in the video each electrode is dipped in its ions solution (Zinc solfate and Cupric solfate respectively).
And yes we are interested in the initial direction of the reaction at Copper half-cell.

 

[Borek]

At first I concentrated on the part you listed, now I started from the beginning. Don't worry about this video, it is poorly thought and simplifies things beyond recognition.

 

[cianfa72]

ok, thus can you confirm that, at least initially, reaction proceed at the Copper half-cell such that copper cations in solution get reduced resulting in slightly positively charged Copper rod (assuming no external connection between electrodes)?

 

[Borek]

That's definitely what I expect would happen.

That is, assuming the idealized case in which rod - when immersed - had no initial charge.

 

[epenguin]

I think it is unnecessary and not very helpful to invoke charge separations.
A Zn atom "wants to" transfer two of its electrons to Cu²⁺
It will do so if it is in contact, as seen this video

(and others, some more confusing).
And it will do so even if not in direct contact but via conductivity as in the galvanic cell, as long as there is a return pathway for electrons which is provided by the salt bridge.

 

[Borek]

Without charge separation there is no potential difference, so you can't ignore it without ignoring physics.