Question

In leaching of alumina from bauxite by Bayer's process, then ore is treated with ______.

Options

• NaOH(aq)

• NaCN(aq)

• KCN(aq)

• Na₂CO₃ (aq)

Answer 1

In leaching of alumina from bauxite by Bayer's process, then ore is treated with NaOH(aq).

Explanation:

In leaching of alumina from bauxite by Bayer's process, the ore is treated with NaOH(aq). Concentration is carried out by heating the powdered ore with a concentrated solution of NaOH at 473 - 523 K and 35-36 bar pressure. This process is called digestion. In this reaction, Al₂O₃ is extracted out as sodium aluminate.

\[\ce{Al2O3(s) + 2NaOH(aq) + 3H2O(l) -> 2Na[Al(OH)4](aq)}\]

The sodium aluminate formed Is neutralised by passing CO₂ gas and hydrated Al₂O₃ is precipitated.

\[\ce{2Na[Al(OH)4](aq) + CO2(g) -> Al2O3 * xH2O(s) + 2NaHCO3(aq)}\]