The electrochemical cell in the diagram is an electrolytic cell used for gold plating. Electroplating is an electrolytic process used to coat metal objects with a more expensive and less reactive metal. The metal to be plated is used as the anode and the electrolyte solution contains the ions of the metal to be plated.
In the diagram, the gold strip on the left is connected to the positive terminal of the battery and is anode. The aluminum glasses on the right is connected to negative terminal of the battery and is cathode. Anode is positive electrode and cathode is negative.
When the power is switched on, the electrolyte solution splits into ions. Positively charged Au³⁺ ions are attracted to the negatively charged cathode, aluminum glasses and slowly deposit on it. The negatively charged ions are attracted to positively charged anode, the gold strip and release electrons. The electrons move through battery towards the cathode.
Au goes into the solution at the anode and get reduced at the cathode, and is thus plated. A constant concentration of Au³⁺ is maintained in the electrolyte solution surrounding the electrodes.
Anode: Au(s) → Au³⁺(aq) + 3e⁻ ............(oxidation)
Cathode: Au³⁺(aq) + 3e⁻ →Au(s) .........(reduction)
