A Levels Chemistry

At the age of 17, in a woodshed in Ohio, Charles Martin Hall discovered the commercial process
for the production of aluminium metal by the electrolysis of a mixture of bauxite, ALO3, and
cryolite, Na,AF6.
What is the main purpose of the cryolite?
A ALO, is covalent, and AIF ions interact with it to produce Al+ ions which can be
discharged at the cathode.
B Cryolite is a base, forming NaAlO, with bauxite, enabling aluminium to be discharged at the
anode.
C Cryolite reduces the melting point of the bauxite.
D Cryolite minimises the release of O2- ions at the graphite anodes, which are otherwise burnt
away to CO.


Electrolysis, Electrode Potentials & Cells | 2003 - M/J - 9701/1 | Q9