Which change occurs at the anode in an operating electrochemical cell?

The change that occurs at the anode in a functioning electrochemical cell is oxidation (loss of electrons).

Explanation:

Electrolysis is the process that uses electrical energy to induce a redox reaction that is not spontaneous. It is carried out in electrolytic cells, which are powered by an external source, (a battery or other source of electrical current). That is, electrolytic cells or cells are known as the containers that contain the dissolved or molten electrolyte in which the electrodes connected to a direct current source from which the electrons come are immersed. In electrolytic cells, the chemical reaction that produces the energy does not happen spontaneously, but the electrical current is transformed into a chemical reaction of oxidation-reduction.

The anode is the electrode that loses electrons in an oxidation reaction. It is normally linked to the positive pole of the transit of electric current.

So, the change that occurs at the anode in a functioning electrochemical cell is oxidation (loss of electrons)