Same chapter3 marksDifficulty: Medium
Name the constituents and one use of brass, bronze and duralumin.
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3 marksDifficulty: Medium
Name the process by which aluminium oxide is obtained pure from bauxite, and write the equations for the two main steps.
Original Khojo Papers practice question — not from a past board paper.
Answer
Baeyer's process. The alumina dissolves in hot sodium hydroxide: Al2O3 + 2NaOH → 2NaAlO2 + H2O. The filtered solution is diluted and seeded so that aluminium hydroxide precipitates: NaAlO2 + 2H2O → NaOH + Al(OH)3↓, and this is heated to give pure alumina.
No citable source has been recorded for this record. Treat it as practice material, not as fact.
Explanation
Iron(III) oxide and silica, the main impurities, do not dissolve and are filtered off.
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