The Hall Héroult process is used to produce what?

1 Answer
Ben G.
Mar 26, 2017

Aluminium.

Explanation:

The Hall-Héroult process is probably the most common method of smelting aluminium industrially.

Alumina (or Aluminium Oxide, #Al_2O_3#), the most common aluminium oxide, undergoes electrolysis hrough the Hall-Héroult process, where alumina is dissolved in molten cryolite (#Na_3AlF_6#) for electrolysis, at around #940^@-980^@# celsius.

At the cathode:
#Al^(3+)+3e^(-) -> Al#

At the anode:
#O^(2-)+C -> CO + 2e^(-)#

Full Equation:
#Al_2O_3 + 3C -> 2Al + 3CO#

As to why the alumina must be dissolved in cryolite rather than just aqueous #Al_2O_3#: hydronium ions in the water will oxidise the elemental aluminium. You may think, "why not use molten alumina?" Well, while this would work, alumina has a melting point of around #2000^@#C. Thus it is dissolved in molten cryolite (MP #~~ 1000^@#C).

PS: natural cryolite is far too rare to be used for electrolysis, so a synthetic version is created from fluorite, a far more common material.

(source)

Related questions
See all questions in Metal Activity Series
Impact of this question
5528 views around the world
You can reuse this answer
Creative Commons License