In an electrolytic cell, how are the cathode and anode labeled compared to a galvanic cell?

In an electrolytic cell, the cathode is labeled negative and the anode is labeled positive. This is opposite to the labeling in a galvanic cell.

The reason for this difference lies in the functioning of these two types of electrochemical cells. In a galvanic cell, which generates electrical energy from spontaneous redox reactions, the cathode (where reduction occurs) is the electrode that attracts cations and is therefore positive, while the anode (where oxidation occurs) is negative, as it donates electrons to the circuit.

Conversely, in an electrolytic cell, which requires an external power source to drive non-spontaneous reactions, the cathode is where reduction takes place. It becomes the site of electron gain and is therefore designated as the negative electrode since it is connected to the negative terminal of the power source. The anode, on the other hand, is where oxidation occurs and is connected to the positive terminal of the power source, making it the positive electrode.

Thus, the labeling of electrodes in an electrolytic cell is based on the flow of electrons induced by the external power supply, distinctly contrasting with the spontaneous reaction process in a galvanic cell.