Baeyer's process is used to concentrate bauxite ore to alumina.
Give balanced chemical equations for the reaction taking place for its conversion from bauxite to alumina.
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Conversion of impure bauxite to sodium aluminate:
$\underset{\text{Amphoteric oxide}}{\underset{\text{[Impure bauxite]}}{\text{Al}_2\text{O}_3.2\text{H}_2\text{O }}} + \underset{\text{Base}}{\underset{\text{[conc. soln]}}{2\text{NaOH }}} \xrightarrow{150 - 200 ^{\circ}\text{C}} \underset{\text{Salt}}{\underset{\text{[sodium aluminate]}}{2\text{NaAlO}_2}} + \underset{\text{Water}}{ \text{3H}_2\text{O}}$
Conversion of sodium aluminate to aluminium hydroxide:
$\underset{\text{[sodium aluminate]}}{\text{NaAlO}_2} + 2\text{H}_2\text{O} \xrightarrow{50 - 60 ^{\circ}\text{C}} \underset{\text{[sodium hydroxide]}}{\text{NaOH}} + \underset{\text{[aluminium hydroxide]}}{\text{Al(OH)}_3}$
Conversion of Al(OH)3 - to pure alumina - heat on Al(OH)3:
$\underset{\text{[aluminium hydroxide]}}{\text{2Al(OH)}_3} \xrightarrow{1100^{\circ}\text{C}} \underset{\text{[pure alumina]}}{\text{Al}_2\text{O}_3} + \text{3H}_2\text{O}$
Precipitated Al(OH)3 is ignited to give pure alumina [Al2O3]