Electrolysis Flashcards
What is electrolysis?
The splitting up of a compound using electricity
What type of compound is electrolysis for?
Ionic compounds
What does electrolysis split a compound into?
A metal and a non metal
What is electrolysis typically for?
Separating a metal from a metal ore
What is a electrolyte?
Either:
- An ionic compound in the molten state
- An ionic compound dissolved in water
What is an electrode?
A charged piece of material used in electrolysis
What is an anode?
A positively charged electrode
What is a cathode?
A negatively charged electrode
What is an aqueous solution?
A solution where the solvent has been dissolved in water
How would you charge an electrode?
With a DC power supply
What happens to the cations during the electrolysis of a molten compound?
They migrate to the cathode where they are reduced
What happens to the anions during the electrolysis of a molten compound?
They migrate to the anode where they are oxidised
What metal oxides would you use electrolysis for?
Those where the metal is more reactive than carbon
What would you do to an insoluble metal oxide prior to electrolysis?
Melt it into molten form
What would you do to a soluble metal oxide prior to electrolysis?
Dissolve it in water
Why can’t electrolysis be done with solids?
Because the ions need to be able to move and cannot do that when a solid
What happens to the cations during the electrolysis of an aqueous solution?
They migrate to the cathode where the least reactive (out of the metal and hydrogen) cation will be reduced
What happens to the anions during the electrolysis of an aqueous solution?
They migrate to the anode where the hydroxide ions will be oxidised unless a halide is present and that will be oxidised instead
What is a redox reaction?
When both oxidation and reduction happen in the same reaction
Write a half equation for the reduction of aluminium (from aluminium oxide)
Al3+ + 3e- —-> Al
What is added to aluminium oxide before electrolysis? Why?
Cryolite, to reduce the melting point
Write a half equation for the oxidation of oxide ions (from aluminium oxide)
2O2- —-> O2 + 4e-
Why would an anode need regularly replacing in electrolysis?
Because any oxygen produced would react with the graphite electrode to produce CO2
