Cambridge O Level Chemistry · Syllabus 5070 · Electrochemistry
Active electrode
What is Active electrode?
An electrode that takes chemical part in the electrolysis instead of merely conducting. A copper anode in aqueous copper(II) sulfate is the required example: the copper of the electrode itself is oxidised and passes into the solution as copper ions, so the anode loses mass and no gas is released there.
This definition is part of the Electrochemistry chapter in Cambridge O Level Chemistry.
Questions students ask about Active electrode
What happens when aqueous copper(II) sulfate is electrolysed with copper electrodes instead of carbon?
Carbon and platinum electrodes are inert: they conduct but take no chemical part, so with carbon electrodes copper is deposited at the cathode and oxygen gas is released at the anode. A copper anode is different: it is an active electrode, so the copper of the anode itself is oxidised and passes into the solution as copper ions, while copper is deposited on the cathode. No gas forms at the anode. Write what is observed: the anode loses mass and the cathode gains mass.