Question

In the extraction of aluminium by Hall-Heroult process, purified \[\ce{Al2O3}\] is mixed with \[\ce{CaF2}\] to:

(i) lower the melting point of \[\ce{Al2O3}\].

(ii) increase the conductivity of molten mixture.

(iii) reduce \[\ce{Al^{3+}}\] into \[\ce{Al(s)}\].

(iv) acts as catalyst.

Answer 1

(i) lower the melting point of \[\ce{Al2O3}\].

(ii) increase the conductivity of molten mixture.

Explanation:

\[\ce{CaF2}\] mixed with purified \[\ce{Al2O3}\] helps in lowering the melting point of \[\ce{Al2O3}\] and increases the conductivity of the molten mixture.