Electrolysis

• What is the process of electrolysis?


  It is the decomposition of a molten ionic compound when an electric current is passed through it.
• What are electrolytic cells used for?


  They are used to facilitate the process of electrolysis.
• What are liquids and solutions that can conduct electricity called?

  Electrolytes
• Why can't covalent compounds undergo electrolysis?


  Because they cannot conduct electricity.
• What are the components of an electrolytic cell?


  • Electrode: metal or graphite rod for current flow
  • Electrolyte: ionic compound in molten or dissolved form
  • Anode: positive electrode
  • Cathode: negative electrode
• What does the acronym PANIC help to remember?


  It helps to remember that Positive is Anode and Negative is Cathode.
• Why can't ionic compounds in solid state conduct electricity?


  Because they have no free ions that can move.
• When can ions in ionic compounds move freely?


  When the compounds are in molten state or dissolved in a solution.
• What happens to ions when an electric current is passed through an electrolyte?


  The ions start to move towards the electrodes.
• What is the direction of movement for positive ions during electrolysis?


  They migrate towards the negatively charged electrode, the cathode.
• What is the direction of movement for negative ions during electrolysis?


  They migrate towards the positively charged electrode, the anode.
• What is the flow of electrons in electrochemistry?


  Electrons flow from the anode to the cathode.
• What is produced at the anode during the electrolysis of lead(II) bromide?


  Bromine gas
• What is produced at the cathode during the electrolysis of lead(II) bromide?


  Lead metal
• What is the method for electrolysis of molten lead(II) bromide?


  1. Heat lead(II) bromide until molten.
  2. Insert two graphite rods as electrodes.
  3. Connect to a power source.
  4. Observe bromine gas at the anode and lead metal at the cathode.
• Why are electrodes in electrolysis often made of inert materials?


  To prevent them from participating in side reactions with the electrolyte.
• What determines the method of extraction for metals?

  The position of the metal on the reactivity series.
• Why do higher placed metals in the reactivity series require electrolysis for extraction?


  Because they are too reactive to be reduced by carbon.
• What is a disadvantage of using electrolysis for metal extraction?


  It is very expensive due to high energy requirements.
• What are the extraction methods for metals based on their reactivity?

  • Most reactive (e.g., Potassium): Extracted by electrolysis.
  • Less reactive (e.g., Zinc, Iron): Extracted by heating with carbon.
  • Least reactive (e.g., Gold): Found as pure elements.
• How is aluminium extracted from its ore?

  By electrolysis of aluminium oxide dissolved in molten cryolite.
• Why is cryolite used in the extraction of aluminium?


  It lowers the melting point of aluminium oxide, reducing energy costs.
• What happens to the anode during the electrolysis of aluminium extraction?


  It wears away due to reaction with oxygen, requiring regular replacement.
• What ions are produced during the dissociation of water in electrolysis?


  H⁺ and OH^- ions.
• What determines which ions get discharged at the electrodes during electrolysis of aqueous solutions?


  The relative reactivity of the elements involved.
• What is produced at the positive electrode if halide ions are present during electrolysis?


  A halogen (chlorine, bromine, or iodine).
• What is produced at the positive electrode if no halide ions are present during electrolysis?


  Oxygen gas.
• What is produced at the negative electrode during electrolysis?


  Either hydrogen gas or a metal, depending on reactivity.
• What happens if the metal is above hydrogen in the reactivity series during electrolysis?


  Hydrogen gas will be produced at the cathode.
• What happens if the metal is below hydrogen in the reactivity series during electrolysis?


  The metal will be produced at the cathode.
• What should you do first when studying the reactivity of ions?


  Write down all of the ions present.
• What ions are attracted to the positive electrode during electrolysis?


  Negatively charged OH ions and non-metal ions.
• What happens if halide ions are present at the anode?


  The halide ion is discharged, loses electrons, and forms a halogen.
• What is produced at the anode if no halide ions are present?


  Oxygen is discharged at the anode.
• What ions are attracted to the negative electrode (cathode)?


  Positively charged H and metal ions.
• What determines whether hydrogen gas or a metal is produced at the cathode?


  The reactivity of the metal compared to hydrogen.
• What occurs if the metal is above hydrogen in the reactivity series?


  Hydrogen gas will be produced at the cathode.
• What happens at the cathode if the positive ions from the ionic compound are less reactive than hydrogen?


  The metal is produced at the cathode.
• What is the first step in predicting products formed during electrolysis?


  Identify the ions attracted to the cathode.
• In the electrolysis of magnesium iodide, which element is discharged at the cathode?


  Hydrogen is discharged at the cathode.