What causes voltage variation in an electrochemical cell?

The variation in voltage in an electrochemical cell is primarily influenced by the type of electrodes used. The electrodes are made from materials that have different tendencies to gain or lose electrons, which is quantified by their standard electrode potentials. Different electrode materials will react differently with the electrolyte, creating variations in the electrochemical reactions occurring at each electrode. This difference establishes a voltage, as the flow of electrons from one electrode to another through an external circuit is driven by the potential difference between the electrodes.

The other factors mentioned, such as the size of the electrolyte container or the presence of a catalyst, do not fundamentally alter the voltage produced by the cell in the same direct manner. The size of the electrolyte container might affect the concentration of ions but does not directly influence the inherent characteristics of the electrodes. Additionally, catalysts can speed up reactions without changing the overall voltage generated by the electrochemical processes occurring at the electrodes. The color of the electrodes does not play a role in voltage variation, as it is a physical property that does not affect the electron transfer capabilities of the materials involved.