Chem end unit test

• What is electrolysis used for?

  To cause a reaction using electrical current
• What does the term 'electrolysis' mean?

  'Splitting up with electricity'
• What happens during electrolysis?

  • Electric current passes through an electrolyte
  • Ions move towards electrodes
  • Compound decomposes
• Where do positive ions move during electrolysis?

  Towards the cathode (-ve electrode)
• What happens to positive ions at the cathode?

  They gain electrons and are reduced
• Where do negative ions move during electrolysis?

  Towards the anode (+ve electrode)
• What happens to negative ions at the anode?

  They lose electrons and are oxidised
• What is created as ions travel to the electrodes?

  A flow of charge through the electrolyte
• What happens to ions as they gain or lose electrons?

  They form uncharged elements and discharge
• Why can't ionic solids be electrolysed?

  • Ions are in fixed positions
  • Ions cannot move
• Why can molten ionic compounds be electrolysed?

  Because ions can move freely
• What is an example of a molten ionic liquid?

  Lead bromide
• What happens to positive metal ions during electrolysis?

  They are reduced to the element at the cathode
• What happens to negative non-metal ions during electrolysis?

  They are oxidised to the element at the anode
• How can metals be extracted from their ores using electrolysis?

  • Used for reactive metals
  • If carbon reduction is not possible
  • Requires significant energy
• What ore is aluminium extracted from?

  Bauxite
• Why is cryolite mixed with aluminium oxide during extraction?

  To lower the melting point
• What compound does bauxite contain?

  Aluminium oxide, Al₂O₃
• What does the molten mixture of aluminium oxide and cryolite contain?

  Free ions that conduct electricity
• What happens to Al³⁺ ions at the negative electrode?

  They gain three electrons and become neutral
• What happens to ions at the positive electrode during electrolysis?

  They lose two electrons