Why do electrons flow from the right to the left in the external circuit of a cell with two Cu electrodes?

The flow of electrons in a galvanic cell can be understood in terms of the electrochemical reactions occurring at the electrodes. In this case, the correct answer relates to the concentration of reactants in the half-cells and their contribution to the cell's overall potential.

When discussing the movement of electrons from the right electrode to the left one, it is important to consider that the left electrode, being more concentrated in CuSO4, leads to a higher reduction potential compared to the right electrode. This means that the left electrode has a greater tendency for reduction reactions to occur, which involves the gain of electrons. Consequently, the right electrode, which may have a less favorable potential (or lower oxidation potential if we are speaking in terms of electron flow), drives electrons from itself toward the left electrode.

This connection underscores that the flow of electrons is motivated by differences in chemical potential and concentration. When there is a higher concentration of CuSO4, it leads to stronger deposition reactions on the left electrode, which contributes to a more favorable reduction and encourages electron flow towards this side. Thus, the electrons flow from the region of the less concentrated solution (right electrode) to the region of more concentrated solution (left electrode), facilitating the electrochemical process.

In contrast