Electrolysis

• What does electrolysis allow us to do with insoluble ionic compounds?

  It allows us to separate the elements in insoluble ionic compounds
• What is an electrolyte?

  A liquid or solution that contains an ionic compound
• Why must the ions in the electrolyte be free to move?

  To allow the electrolysis process to occur
• How would you prepare an electrolyte from a soluble ionic compound like copper sulfate?

  Dissolve it in water
• What must you do to prepare an electrolyte from an insoluble ionic compound like lead bromide?

  Heat it until it melts
• What ions are present in molten lead bromide?

  Positive lead ions and negative bromide ions
• What are the electrodes used in electrolysis generally made of?

  Metal or carbon
• What is the purpose of the power supply in electrolysis?

  To drive the flow of electrons
• What does the term electrolysis literally mean?

  Splitting up with electricity
• What happens to the negative bromide ions during electrolysis?

  They are attracted to the positive anode and discharged
• What do bromide ions form when they are discharged at the anode?

  Bromine gas
• What happens to the positive lead ions during electrolysis?

  They are attracted to the negative cathode and discharged
• What do lead ions form when they are discharged at the cathode?

  Pure lead
• What is happening to the bromide ions at the anode?

  They are being oxidized to bromine
• What is happening to the lead ions at the cathode?

  They are being reduced to form pure lead
• How do electrons move during the electrolysis process?

  From the bromide ions to the lead ions through the wire
• What is the overall purpose of electrolysis in this context?

  To convert the ions in a compound back into their pure elemental forms
• What are the steps involved in the electrolysis of molten lead bromide?

  1. Prepare molten lead bromide as the electrolyte.
  2. Connect electrodes (anode and cathode) to a power supply.
  3. Pass electric current through the electrolyte.
  4. Bromide ions are oxidized at the anode to form bromine gas.
  5. Lead ions are reduced at the cathode to form pure lead.
• What are the roles of the anode and cathode in electrolysis?

  • Anode: Positive electrode where oxidation occurs (bromide ions to bromine).
  • Cathode: Negative electrode where reduction occurs (lead ions to lead).
• What process is used to extract reactive metals from their oxides?

  Electrolysis
• Why do metals often exist as oxides?

  Because they react with oxygen in the environment
• What is the purpose of reducing the metal in the oxide?

  To remove the oxygen and isolate the pure metal
• Which method is used to reduce metals that are less reactive than carbon?

  Reduction with carbon
• What is the limitation of using carbon for reduction?

  It only works for metals less reactive than carbon
• Why can't aluminium oxide be used directly in electrolysis?

  Because it is solid and the ions are fixed in place
• What must be done to aluminium oxide before electrolysis can occur?

  It must be melted into a molten state
• What is the melting point of aluminium oxide?

  Over 2000 degrees Celsius
• What is the role of cryolite in the electrolysis process?

  It lowers the melting point of aluminium oxide
• What equipment is needed for the electrolysis of molten aluminium oxide?

  A beaker, two carbon electrodes, and a power source
• What happens to oxygen ions at the anode during electrolysis?

  They lose electrons and are discharged as oxygen atoms
• What is the charge of aluminium ions in the electrolyte?

  Aluminium ions are three plus ions
• What is the mnemonic to remember the difference between oxidation and reduction?

  Oil rig (Oxidation is Loss, Reduction is Gain)
• What is the overall equation for the electrolysis of aluminium oxide?

  Aluminium oxide (liquid) → Aluminium (liquid) + Oxygen (gas)
• What are the steps involved in the electrolysis of aluminium oxide?

  1. Purify aluminium oxide from bauxite
  2. Mix with cryolite to lower melting point
  3. Melt the mixture to create molten aluminium oxide
  4. Set up electrolysis equipment with electrodes and power source
  5. Conduct electrolysis to produce aluminium and oxygen
• What are the roles of the anode and cathode in the electrolysis of aluminium oxide?

  • Anode: Positive electrode where oxidation occurs (oxygen ions lose electrons)
  • Cathode: Negative electrode where reduction occurs (aluminium ions gain electrons)
• What is the significance of the melting point in the electrolysis of aluminium oxide?

  • Must be molten for ions to move
  • Requires high temperatures (over 2000°C)
• What is electrolysis used for?

  To split compounds into their elements
• How is electrolysis performed?

  By passing an electric current through an electrolyte
• What must be true for the ions in an electrolyte for electrolysis to work?

  The ions must be free to move around
• What must be done to insoluble compounds for electrolysis?

  They must be melted to form a molten liquid