products formed by electrolysis

• Metals


  Produced at the cathode
• Non-metals


  Produced at the anode
• Electrolysis of molten ionic compound

  1. Metal forms at the cathode

  2. Non-metal forms at the anode
• Metal ions


  Have a positive charge, so they're attracted to the negative cathode
• Non-metal ions


  Have a negative charge, so they're attracted to the positive anode
• Molten lead bromide electrolysis

  • Lead produced at the cathode
  • Bromine produced at the anode
• In aqueous solutions


  Hydrogen ions are attracted to the cathode
• Water molecules break down into hydrogen ions (H+) and hydroxide ions (OH–) during electrolysis
• Positively charged hydrogen ions

  Attracted to the negative cathode
• Positive metal ions from the electrolyte


  Attracted to the cathode
• At the cathode


  Either the metal or hydrogen gas is produced
• We can use the reactivity series to predict whether hydrogen gas or the metal will be produced
• If the metal is less reactive than hydrogen


  The metal will be produced
• Electrolysis of copper chloride solution

  • Copper forms at the cathode
  • Chlorine gas at the anode
• If the metal is more reactive than hydrogen


  Hydrogen gas will be produced
• Electrolysis of sodium chloride solution

  • Hydrogen gas forms at the cathode
  • Chlorine gas at the anode
• In aqueous solutions


  Hydroxide ions are attracted to the anode
• Water breaks down into hydrogen ions (H+) and hydroxide ions (OH–) during electrolysis
• Negatively charged hydroxide ions

  Attracted to the positive anode
• At the anode


  Hydroxide ions lose electrons and form oxygen gas
• If no halide ions present

  Oxygen gas is produced at the anode
• Electrolysis of sodium sulfate solution

  • Oxygen gas forms at the anode
  • Hydrogen gas forms at the cathode
• Electrolysis of acidified water produces hydrogen and oxygen
• Electrolysis of acidified water

  1. H+ ions attracted to cathode, gain electrons to form H2 gas

  2. OH- ions lose electrons at anode, form O2 gas
• Electrolysis of aqueous copper sulfate produces copper and oxygen gas
• Electrolysis of aqueous copper sulfate

  1. Cu2+ ions gain electrons at cathode to form solid copper

  2. OH- ions lose electrons at anode, form O2 gas
• Copper purification by electrolysis

  • Impure copper used as anode
  • Small pure copper used as cathode
  • Aqueous copper sulfate used as electrolyte
  • Copper atoms from impure anode become part of electrolyte
  • Cu2+ ions attracted to cathode, gain electrons to form solid copper
  • Impurities form sludge under anode as it corrodes