Electrochemistry

• What is electrolysis?

  Breakdown of molten or aqueous ionic compound by electricity
• What is the equation of hydroxide when being discharged?

  4OH- --> O2 + 2H2O + 4e
• Uses of:

  NaOH: Make soaps, detergent and dye

  Chlorine: Make PVC, bleaches, kill bacteria in swimming pool

  Hydrogen: Make ammonia and as a fuel
• What is an electrode?

  Conductors which conduct electricity due to presence of free moving electrons
• What is an electrolyte?

  Ionic compound in molten and aqueous state contains freely moving ions and can conduct electricity
• Application of electrolysis:

  Extraction of aluminum - Oxygen formed at anode react with carbon to carbon dioxide, carbon anode is corroded and needs to be replaced
• Hydrogen-Oxygen Fuel Cell:

  Uses hydrogen and oxygen to produce electricity with water as the only chemical product
• Advantages of Hydrogen-Oxygen Fuel Cell:

  • Doesn't cause pollution
  • Hydrogen is a renewable resource, can be obtained by electrolysis of water
  • Efficient source of energy
• Disadvantages of Hydrogen-Oxygen Fuel Cell:

  • Hydrogen is extremely flammable and explosive
  • Obtaining hydrogen through electrolysis is costly
  • Hydrogen is very light and require high storage volume
• Process of electrolysis (Molten Lead (II) Bromide)

  1. Bromine ion moves to positive terminal (anode) and discharges by donating electron, oxidation occurs
  2. Lead ion moves to negative terminal (Cathode) and discharges by accepting electron, reduction occurs
• Process of electrolysis (active electrode)

  1. Active electrode (copper) take part in electrolysis by donating electrons
  2. Copper ions flow into solution while copper anode is corroded
  3. Copper ions accept electrons to form copper, copper cathode becomes thicker
• Process of electrolysis (purification)

  1. Impure copper at anode, pure copper at cathode
  2. When impure copper is immersed into copper (II) sulfate solution, copper atoms dissolve to form copper (II) ions by donating electron
  3. Copper (II) ions accept electrons to form copper at the cathode, cathode becomes thicker.
  4. Pure copper is collected at the cathode
• Process of electrolysis (Electroplating a jug with silver)

  1. Set silver as anode, silver nitrate as electrolyte
  2. Silver anode dissolves to form silver ions by donating electrons
  3. Silver ion accepts electrons to form silver, a layer of silver formed around the jug
• Electrolysis of Aluminum

  1. Carbon anode and molten aluminium oxide
  2. Oxygen formed at anode react with carbon to form CO2, carbon anode corroded and needs to be replaced