Question

For each substance listed below, explain its significance in the extraction of aluminium

Sodium hydroxide

Answer 1

1. Extraction of aluminum from Bauxite ore is done by Baeyer's process.
2. During extraction of Aluminum, to convert any ferrous oxide present in ore into ferric oxide the ore is roasted at a low temperature.
3. Roasted ore is now digested with a hot and concentrated solution of Sodium hydroxide($\mathrm{NaOH}$) at high pressure and $150°\mathrm{C}$ temperature.
4. Here Aluminum oxide, ${\mathrm{Al}}_2{\mathrm{O}}_3$ is converted to Sodium aluminate (${\mathrm{NaAlO}}_2$) by the reaction -${\mathrm{Al}}_2{\mathrm{O}}_3.2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{s}\right)+2\mathrm{NaOH}\left(\mathrm{aq}\right)\to 2{\mathrm{NaAlO}}_2\left(\mathrm{aq}\right)+3{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$.