Electrolysis Principles

• When an electric current is passed through a molten ionic compound the compound decomposes or breaks down

  • The process also occurs for aqueous solutions of ionic compounds
• Covalent compounds cannot conduct electricity hence they do not undergo electrolysis
• Ionic compounds in the solid state cannot conduct electricity either since they have no free ions that can move and carry the charge

  A) solid

  B) molten/solution

  
• Electrode - a rod of metal or graphite through which an electric current flows into or out of an electrolyte
• Electrolyte - the ionic compound in a molten or dissolved solution that conducts the electricity
• Anode - the positive electrode of an electrolysis cell
• Anion - a negatively charged ion which is attracted to the anode
• Cathode - the negative electrode of an electrolysis cell
• Cation - a positively charged ion which is attracted to the cathode
• Electrylotic cell set up

  A) positive cations

  B) negative cathode

  C) power supply

  D) negative ions

  E) gain

  F) lose

  G) positive anode

  H) electrolyte solution

  
• Metals and hydrogen form positively charged ions and so either a metal or hydrogen gas is formed at the cathode
• Non-metals form negatively charged ions and so non-metals (except hydrogen)are formed at the anode
• Use the PANIC mnemonic to remember which electrode is the positive and which is the negative: Positive (is) Anode Negative Is Cathode
• During electrolysis, current needs to flow around the circuit:

  • In order for this to occur, charge must be transferred around the circuit (current is a measure of the rate of flow of charge) by charge carriers
  • The power supply provides the cathode with a supply of electrons, causing it to become negatively charged
  • Positive ions (cations) in the electrolyte move towards the cathode where they gain electrons
  • Negative ions (anions) in the electrolyte move towards the anode where they lose electrons
  • The electrons move from the anode back towards the power supply
• In a complete circuit:

  • Electrons are the charge carriers in the external circuit
  • Ions are the charge carriers in the electrolyte
• Movement of electrons and ions in the electrolysis of NaCl

  A) flow of electrons

  B) cathode

  C) cation

  D) anode

  E) anion

  F) electrolytic

  G) solution

  
• Electrolysis - the decomposition of an ionic compound, when molten or aqueous solution- by passing of an electric current

  • This is possible due to the presence of mobile electrons/free-moving ions
• An electrolyte is a molten or aqueous substance that undergoes electrolysis
• Electrodes - Metal or graphite rods that aid the flow of electricity in and out of the electrolyte

  • Anode: Positive electrode
  • Cathode: Negative Electrode
  • (PANIC: Positive is Anode, Negative is Cathode)
• Anion - Negatively charged ion that moves to anode
• Cation - Positively charged ion that moves to the cathode
• Reactive electrodes participate in the reaction, while inert electrodes (Graphite, Carbon) do not react with the cations or

  A) positive

  B) anode

  C) negative

  D) cathode

  E) negatively charged

  F) losing electrons

  G) positively charged

  H) gaining electrons

  I) electrolyte

  
• Positive and negative ions in an ionic compound attract eachother strongly
• Ionic compound solids cannot conduct as the ions are not free
• Electrolysis - decomposition of an ionic compound when in molten or in aqueous, by the passage of electric current
• Lysis - splitting
• Electrolysis uses:

  • purification of copper
  • plating metals w/ silver or gold - jewellery
  • extracting reactive metals e.g. aluminium
• Ions carry the charge
• Electrolysis set up

  A) e-

  B) e-

  C) electrolyte

  D) ions

  E) e-

  F) electrode

  
• Electrolysis set up as scientific diagram

  A) power pack

  B) wires

  C) e-

  D) electrolyte

  E) ions

  F) positive ions

  G) cations

  H) electrode

  I) negative ions

  J) anions

  K) anode

  L) cathode

  
• What happens during electrolysis

  A) battery

  B) anode

  C) cathode

  D) wires

  E) negative

  F) positive

  G) oxidation

  H) anode

  I) positive

  J) negative

  K) gain

  L) lose

  M) reduction

  N) cathode

  O) heat

  
• Electrolyte - a substance that conducts electricity when in the molten state or in solution

  • Electricity is carried through the electrolyte by ions
• In molten and in solution, the ions are free to move to the electrodes

  • electrons flow through the wires in the external circuit
• Electrolytes are composed of ions but in solid state, the ions are rigidly held in regular positions and are unable to move to an electrode
• Melting or dissolving the electrolyte in water causes the breakdown of ionic lattics and the ions are free to move
• Electrolytes include: acids, metal oxides, metal hydroxides and salts

  A) strong

  B) more ions

  C) fully dissociate

  D) hydroxide

  E) chloride

  F) hydrochloric

  G) weak

  H) less ions

  I) incompletely dissociate

  J) water

  K) acetic

  L) ammonia

  M) non-electrolytes

  N) no ions

  O) don't dissociate

  P) sugar

  Q) alcohol

  R) oil

  
• Electrodes - conduct electricity e.g. metals/graphite
• Inert - don’t react with electrolytes aka electrodes
• Cathode - negative electrode
• Anode - positive electrode