Electrolysis to extract metals from oxides Flashcards
(14 cards)
Why can’t aluminium oxide be reduced by carbon?
Aluminium is more reactive than carbon, so it must be extracted using electrolysis.
What is electrolysis used for in metal extraction?
To separate reactive metals from their oxides
Why must aluminium oxide be molten for electrolysis?
Because ions must be free to move for electrolysis to work.
Why is cryolite used in aluminium extraction?
It lowers the melting point of aluminium oxide, reducing energy costs.
What are the ions in molten aluminium oxide?
Al³⁺ (aluminium ions) and O²⁻ (oxide ions).
Where do aluminium ions go during electrolysis?
To the cathode, where they gain electrons and are reduced to aluminium metal.
Where do oxide ions go during electrolysis?
To the anode, where they lose electrons and form oxygen gas.
What happens at the cathode in aluminium electrolysis?
Al³⁺ + 3e⁻ → Al (aluminium is reduced).
What happens at the anode in aluminium electrolysis?
2O²⁻ → O₂ + 4e⁻ (oxide ions are oxidised to oxygen gas).
What is the overall equation for aluminium extraction?
2Al₂O₃ (l) → 4Al (l) + 3O₂ (g)
Why is electrolysis expensive?
It requires large amounts of energy to melt compounds and power the process.
What does ‘oxidation’ mean in electrolysis?
Loss of electrons. Example: O²⁻ → O₂ + e⁻.
What does ‘reduction’ mean in electrolysis?
Gain of electrons. Example: Al³⁺ + 3e⁻ → Al.
What does the mnemonic ‘OIL RIG’ stand for?
‘Oxidation Is Loss’ and ‘Reduction Is Gain’ of electrons.
