Electrolysis

• Electrolysis


  The decomposition of an ionic compound when molten or in Aqua Solution by the passage of an electric current
• Electrolysis


  • Ionic compound should be either melted or in water so that they have free ions in order to allow electricity to pass through
• Electrode


  A conductor, often a metal or graphite Rod, that allows electric current to go in or out of an electrolyte
• Electrolyte

  The molten or aquous substance that undergoes electrolysis
• Molten


  Heated until it becomes a liquid
• Aquous


  Dissolved in water
• Cation


  A positively charged ion formed when an atom loses electrons
• Anion


  A negatively charged ion formed when an atom gains electrons
• Cathode


  The negative electrode that attracts positively charged cations
• Anode


  The positive electrode that attracts negatively charged anions
• Cathode

  Attracts positive cations
• Anode

  Attracts negative anions
• Electrolysis

  1. Electric current flows through the circuit

  2. Electrons move from power supply to cathode making it negatively charged

  3. Anode becomes positively charged as it loses electrons

  4. Positive cations in electrolyte move to cathode and gain electrons

  5. Negative anions in electrolyte move to anode and lose electrons

  6. Electrons from anode move back to power supply
• In the electrolyte, it is the ions that move and carry the electrical charge
• Positive cations will always move towards the cathode
• Negative anions will always move towards the anode
• Electrolyte can be either a molten compound or an aquous solution
• A binary compound is a chemical compound composed of two different elements
• Molten compounds are in a liquid state due to being heated to a high temperature, typically above their melting points
• Oxidation at the anode


  Negative ions lose electrons
• Reduction at the cathode

  Positive ions gain electrons
• Oxidation is the loss of electrons, reduction is the gain of electrons
• Ionic half equations for electrolysis of molten sodium chloride


  • At anode: 2Cl- -> Cl2 + 2e-
  • At cathode: Na+ + e- -> Na
• Electrolysis


  The process of using electricity to drive a chemical reaction
• Inert electrodes


  • Made of platinum or carbon graphite
  • Don't get involved in the chemical reactions
  • Avoid interference
• Molten compound


  Substance in a liquid state resulting from being heated above its melting point
• Free ions


  Can carry charge during electrolysis
• Electrolysis of molten lead(II) bromide

  1. Connect electrodes to power supply

  2. Bromide ions travel to positive electrode (anode)

  3. Bromine gas forms at anode

  4. Lead ions travel to negative electrode (cathode)

  5. Lead forms at cathode
• Aqueous solution


  Substance mixed with water
• Ions in aqueous electrolyte

  • Cations from dissolved substance
  • Anions from dissolved substance
  • Hydrogen ions
  • Hydroxide ions
• Discharge at electrodes


  • Metals or hydrogen at cathode
  • Non-metals other than hydrogen at anode
• Reactivity series


  List of metals arranged in order of their reactivity
• Electrolysis of aqueous sodium chloride

  1. Hydrogen ions discharged at cathode

  2. Chlorine gas formed at anode

  3. Sodium and hydroxide ions remain in solution
• Electrolysis of dilute sulfuric acid

  1. Hydrogen gas formed at cathode

  2. Oxygen gas formed at anode
• Hydroxide ions are discharged at anode if no halide ions present
• Halogen gas formed at anode if halide ions in concentrated solution, otherwise oxygen gas formed
• Electrolysis


  The process of using electricity to drive a chemical reaction
• Inert electrodes


  • They don't get involved in the chemical reactions, avoiding any interference
• Molten compounds


  Substances in a liquid state resulting from being heated above their melting points
• Molten compounds have


  Free ions that can carry charge during electrolysis