Electrolysis

• Investigating what happens when aqueous solutions undergo electrolysis

  1. Pour approximately 50 cm³ of copper(II) chloride solution into a beaker

  2. Place a plastic petri dish with two holes over the beaker

  3. Insert a carbon graphite rod into each hole (electrodes)

  4. Attach crocodile leads to the rods and connect to a low-voltage power supply

  5. Select 4 volts on the power supply and switch it on
• Electrodes


  • Carbon graphite rods are unreactive (inert)
  • The two electrodes must not touch each other to avoid a short-circuit
• Copper is less reactive than hydrogen


  Copper is discharged at the cathode
• Electrolyzing a solution containing a halide ion


  The halogen is discharged at the anode
• Holding a piece of damp blue litmus paper near the anode shows the gas produced is chlorine (it becomes bleached)
• Summary of electrolyzing copper(II) chloride solution

  • Copper discharged at the cathode
  • Chlorine gas discharged at the anode
• Investigating electrolysis of sodium chloride solution

  1. Pour approximately 50 cm³ of sodium chloride solution into a beaker

  2. Turn on the low-voltage power supply
• Sodium is more reactive than hydrogen


  Hydrogen gas is discharged at the cathode
• The gas produced at the cathode can be tested with a lit splint to confirm it is hydrogen (produces a squeaky pop)