The process of electrolysis

• what is electrolysis?

  • passing of an electric current through ionic substances that are molten or in solution to break them down into elements
  • ions are discharged at electrodes to produce these
• what is an electrolyte?

  liquid/solution which conducts electricity
• what is a cathode and what is an anode?

  • c - negative electrode
  • a - positive electrode
• what occurs at the cathode and what occurs at the anode during electrolysis?

  • c - reduction occurs
  • a - oxidation occurs
• in aqueous electrolysis, which element is discharged at the cathode? oxygen is produced at the anode unless what?


  • less reactive element discharges at the cathode, hydrogen is produced unless there is a less reactive metal in which the metal is produced
  • oxygen is produced at anode unless the solution contains halide ions in which halogen molecules are produced
• how is aluminium manufactured? why is it expensive?

  • made through the electrolysis of aluminium oxide and cryolite
  • lots of energy is needed to produce the current in electrolysis which makes this process expensive
• half equations in the extraction of aluminium

  • Al3+ + 3e- > Al (cathode)
  • 2O2- >O2 + 4e- (anode)
  • oxygen reacts with C of the anode producing CO2
• why is cryolite used in manufacturing of aluminium?

  lowers the melting point of aluminium oxide, reducing energy costs
• what are the half equations in electrolysis of the aqueous Na2SO4?

  • 2H+ + 2e- > H2 (cathode)
  • 4OH- > 2H2O + O2 + 4e- (anode)
• what are the half equations in electrolysis of the molten and aqueous KCl?

  • K+ + e- > K (cathode)
  • 2Cl- > Cl2 + 2e- (anode)
  • 2O2- > O2 + 4e- (anode)
  • 2H+ + 2e- > H2 (cathode)
• half equations in electrolysis of the aqueous CuBr2


  • Cu2+ + 2e- > Cu (cathode)
  • 2Br- > Br2 + 2e- (anode)