Electron flow direction?
In a galvanic cell, the electrons flow from the less noble metal to the more noble metal due to the electrode potential difference, reducing the ions in the electrolyte at the positive pole. In electrolysis, it's the other way around: oxidation occurs at the positive pole and reduction at the negative pole. However, my teacher said that the electrons still flow from the negative to the positive pole. I don't quite understand that. I know it's the voltage source, but in that case the electrons flow from the positive pole to the negative pole and not the other way around. It would be really nice if someone could explain to me in more detail and in a way that I can understand, ie what the voltage source does exactly (apart from supplying energy for the endergonic reaction, which I know about). The direction of electron flow is just confusing me.
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Your teacher is right, of course. BUT – while a galvanic cell is a "voluntary" process, electrolysis is a forced process.
The negative pole is always where reduction occurs, and the positive pole is where oxidation occurs. These pairs of terms therefore belong together.
In the first case, the less noble metal releases electrons, and cations dissolve. At this pole, there is an excess of electrons ("negative pole"), and the electrons flow through the conductor to the more noble metal, ie, to the location of the electron deficiency.
In electrolysis, a positive and a negative pole are provided. Anions in the solution move to the positive pole and are oxidized there, while cations in the solution move to the negative pole and are reduced.
A flow of electrons (from one pole to the other) is only desired during the discharge process.
In electrolysis, one wants to force a chemical reaction at the poles, i.e. one wants to maintain the electron surplus and deficiency in the poles.
But in general, electrons always flow from the negative to the positive pole (if you let them).
But if the anions are oxidized at the positive pole, the electrons pass through the conductor to the negative pole and reduce the cations there, right? They're needed there, I thought, so how can they still come from the negative pole?