The Hall Héroult process is used to produce what?

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The Hall Héroult process is used to produce what?

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Answer 1 · 2017-03-26T23:03:20

Aluminium.

Explanation:

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

Alumina (or Aluminium Oxide, $A l_{2} O_{3}$ $Al_2O_3$ ), the most common aluminium oxide, undergoes electrolysis hrough the Hall-Héroult process, where alumina is dissolved in molten cryolite ( $N a_{3} A l F_{6}$ $Na_3AlF_6$ ) for electrolysis, at around $940^{\circ} - 980^{\circ}$ $940^@-980^@$ celsius.

At the cathode:
$A l^{3 +} + 3 e^{-} \to A l$ $Al^(3+)+3e^(-) -> Al$

At the anode:
$O^{2 -} + C \to C O + 2 e^{-}$ $O^(2-)+C -> CO + 2e^(-)$

Full Equation:
$A l_{2} O_{3} + 3 C \to 2 A l + 3 C O$ $Al_2O_3 + 3C -> 2Al + 3CO$

As to why the alumina must be dissolved in cryolite rather than just aqueous $A l_{2} O_{3}$ $Al_2O_3$ : 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 $2000^{\circ}$ $2000^@$ C. Thus it is dissolved in molten cryolite (MP $\approx 1000^{\circ}$ $~~ 1000^@$ 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.

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The Hall Héroult process is used to produce what?

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