Electrolysis

• Inert electrodes


  Unreactive electrodes
• Molten salts and aqueous solutions can be electrolysed
• Electrolysis of molten salts and aqueous solutions

  Use inert electrodes
• Sodium can be electrolysed
• Products formed at the cathode and anode during electrolysis of sodium

  • Cathode: Sodium
  • Anode: Oxygen
• Ions present in water

  H+, OH-
• Electrolysis of copper chloride solution

  1. Cathode: Copper formed

  2. Anode: Chlorine formed
• Copper ions (Cu2+)


  Change into copper atoms by gaining electrons
• Chloride ions (Cl-)


  Change into chlorine molecules by losing electrons
• Chloride ions form covalent bonds to produce chlorine molecules
• Overall decomposition of copper chloride during electrolysis

  CuCl2 -> Cu + Cl2
• In electrolysis of sodium chloride solution, hydrogen is produced at the cathode and chlorine at the anode
• Sodium is not produced at the cathode


  Because hydrogen is more reactive than sodium
• The solution left at the end of electrolysis of sodium chloride is sodium hydroxide
• In electrolysis of sodium sulfate solution, hydrogen is produced at the cathode and oxygen at the anode
• Products formed during electrolysis of potassium chloride solution

  • Cathode: Hydrogen
  • Anode: Chlorine
• The solution left at the end of electrolysis of potassium chloride is potassium hydroxide
• Ions present in copper sulfate solution

  Cu2+, SO42-, H+, OH-
• During electrolysis of copper sulfate with graphite electrodes, copper is deposited at the cathode
• Reaction at the cathode

  Cu2+ + 2e- -> Cu (Reduction)
• At the anode, oxygen gas is produced
• The substance left in the solution at the end of electrolysis is sulfuric acid (H2SO4)
• Non-electrolytes do not dissociate into ions when dissolved in water.
• Electrolytes are substances that conduct electricity when dissolved or molten.