Electrolysis of Copper II CuSO4 solution, using: 1. Graphite or platinum, 2. Copper

Here is an explanation of the electrolysis of copper(II) sulfate (CuSO_4) solution for the two specified electrode types. The ions present in an aqueous solution of copper(II) sulfate are Cu^2+(aq), SO_4^2-(aq), and from the dissociation of water, H^+(aq) and OH^-(aq). 1. Using Graphite or Platinum Electrodes (Inert Electrodes) At the Cathode (Negative Electrode): Cations present are Cu^2+ and H^+. Copper(II) ions are more easily reduced than hydrogen ions. Cu^2+(aq) + 2e^- Cu(s) Observation: A reddish-brown deposit of copper metal forms on the cathode. At the Anode (Positive Electrode): Anions present are SO_4^2- and OH^- (from water). Hydroxide ions (or water) are more easily oxidized than sulfate ions. 2H_2O(l) O_2(g) + 4H^+(aq) + 4e^- Observation: Colorless gas (oxygen) is produced at the anode. The solution becomes more acidic due to the formation of H^+ ions. Overall Reaction: 2CuSO_4(aq) + 2H_2O(l) 2Cu(s) + O_2(g) + 2H_2SO_4(aq) Observation: The blue color of the CuSO_4 solution fades as Cu^2+ ions are removed, and the solution becomes acidic. 2. Using Copper Electrodes (Active Electrodes) At the Cathode (Negative Electrode): Cations present are Cu^2+ and H^+. Copper(II) ions are more easily reduced than hydrogen ions. Cu^2+(aq) + 2e^- Cu(s) Observation: A reddish-brown deposit of copper metal forms on the cathode. At the Anode (Positive Electrode): The anode itself is made of copper, which is an active electrode. Copper metal is more easily oxidized than water or sulfate ions. Cu(s) Cu^2+(aq) + 2e^- Observation: The copper anode gradually dissolves, and its mass decreases. Overall Reaction: Cu(s) (anode) Cu(s) (cathode) The net effect is the transfer of copper from the anode to the cathode. The concentration of CuSO_4 in the solution remains relatively constant because Cu^2+ ions are consumed at the cathode and produced at the anode at the same rate. This process is used for refining copper.