Chapter 14.3 Extraction of Aluminium Flashcards
Main ore of aluminium
Bauxite
What substance undergoes electrolysis to obtain alunminium and formula
Aluminium oxide (Al2O3)
What is aluminium oxide dissolved into and name formula
Cryolite - Sodium Aluminium Flouride
What container is used for electrolysis of al2o3
Steel cell
What is the cathode in al2o3 and where is it
Carbon cathode - lining
What is the anode in al2o3 and where is it
3 suspended carbon anodes
Al2O3 —> gives what (ionic equation)
Al 3+ + O 2-
Half equation at cathode (al2o3) and what type of reaction (redox)
4Al3+ + 12e —> 4Al (reduction)
Half equation at anode (al2o3) and what type of redox
6O 2- —> 3O2 + 12e (oxidation)
What is the third reaction that happens in al2o3 electrolysis and between what
the carbon anode and oxygen bubbles
C + O2 —> CO2
Why must the carbon anodes be constantly replaced
They are constantly reacting with O2 and being used up
Why is a solution of aluminium oxide in molten cryolite used rather than molten aluminium oxide?
(aka why is cryolite used)
Reduces the operating temperature of the cell
,
Makes the electrolyte a better conductor
How does aluminium resist the acids in foods when it is used to make food containers
Prevents corrosion because of the oxide layer present on it
Explain why aluminium reacts so slowly
has an UNREACTIVE oxide layer
