In the extraction of aluminium from bauxite the first step is the dressing of the ore by Baeyer's process. Give balanced equations for the conversion of impure bauxite to pure alumina using a concentrated solution of `NaOH`.

Explanation

`Al _(2) O _(3) + 2 Na OH to 2 Na AlO _(2) + H _(2)O`
`Na AlO _(2) + 2 H _(2) O to Na OH + Al (OH) _(3)`
`2Al(OH) _(3) to Al _(2) O _(3) + 3 H _(2)O`
` Al _(2) O _(3) to 2 Al ^(3+) + 3 O ^(2-)`
At cathode: `2 Al ^(3+) + 6e ^(-) to 2Al`
At anode `3 O ^(2-) - 6e ^(-) to 3 O _(2)`