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The pair of oxides which can be leached ...

The pair of oxides which can be leached out when powdered bauxite containing certain impurities is digested with concentrated solution of NaOH at 473-523 K temperature and 35 -36 bar pressure are

A

`TiO_(2),SiO_(2)`

B

`SiO_(2),Al_(2)O_(3)`

C

`SiO_(2),Fe_(2)O_(3)`

D

`Al_(2)O_(3),Fe_(2)O_(3)`

Text Solution

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The correct Answer is:
B
Bauxite is the most important ore of aluminium contains only 30-60% `Al_(2)O_(3)` the rest being a mixture of `SiO_(2),Fe_(2),O_(3)` and `TiO_(2)` . The powdered bauxite is treated with concentrated solution of NaOH resulting in the dissolution of `AI_(2)O_(3)` and `SiO_(2)` while the other oxides (`Fe_(2)O_(3)` and ` TiO_(2))` being basic remain insoluble in NaOH . Hence only `SiO_(2)` and `AI_(2)O_(3)` leached out.
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