Electrolysis Flashcards
What is electrolysis used for and why is it so expensive?
- used for metals HIGH in the reactivity series
* more expensive because it requires more energy
Electrolysis is the extraction of…?
Aluminium
At the cathode what type ions are attracted in electrolysis?
Cations
At the anode in electrolysis what type if ions are attracted?
Anions
Aluminium is unreactive, state 3 of it’s uses… (They don’t rust!)
Car bodies
Window frames
Structures
Why does aluminium seem unreactive?
OXIDE LAYER
What does the oxide layer on aluminium prevent?
Oxide layer prevents chemicals from colliding with aluminium. If the oxide later is removed, aluminium will react quite vigorously.
Why can’t you use carbon to extract aluminium?
Carbon is lower in the reactivity series.
Why do the anodes need continuously replacing? (4)
- oxygen forms at the carbon anode
- carbon reacts with the oxygen to form carbon dioxide gas
- carbon electrode therefore gradually disappears
What temperature does electrolysis occur at?
955’c
Why do the carbon electrodes need to be replaced?
Burns away
Name a metal that can be added to aluminium to make an alloy…
Magnesium
What is the overall equation for ELECTROLYSIS OF ALUMINIUM OXIDE?
2Al2O3 -> 4Al + 3O2
Electrode equation at the cathode..
Al3+ + 3e -> Al
Electrode equation at the anode..
2O2- -> O2 + 4e-
What is cryolite?
A mixture of cryolite and aluminium oxide has a lower melting point than pure aluminium.
Give 4 properties of aluminium…
- low density
- strong
- ductile
- malleable
How does electrolytic reduction work in the extraction of aluminium?
Electricity is used to reduce aluminium oxide.
What kind if metals is electrolysis used for?
Metals high up in the reactivity series
When molten lead bromide undergoes electrolysis what forms at the cathode?
Grey solid coating on the electrode
What is the electrode equation at the cathode? (Lead bromide)
Pb2+ + 2e- = Pb (Pb gains electrons; REDUCTION)
What is the electrode equation at the anode (lead bromide)
2Br- = Br2 + 2e- (lose electrons; oxidation)
When molten lead bromide undergoes electrolysis what forms at the anode?
Bubbling and orange gas given off.
