This loosely held copper could be lost in handling the electrode. This difficulty is prevented by adding an excess of nitrate ion to the solution. The reduction of nitrate to ammonium ion occurs prior to that of hydrogen thus buffering the cathode potential and preventing evolution of hydrogen gas. Both an anodic and a cathodic reaction must occur for current to pass through the electrolysis cell. In this experiment, the oxidation of water could be the anodic reaction.
Greater efficiency is obtained by addition of a small amount of urea.
The urea is oxidized at the anode and serves as a depolarizer . This is prepared for you. Obtain a copper ore unknown from your instructor. Dry the sample from between 100 o C and 120 o C for two hours and cool the dried sample in the desiccator. Turn your student I.D. card into your instructor and in return obtain from your instructor two platinum cathodes, two platinum anodes, and two tall-form electrolytic beakers.