Question

(a) Write chemical equations for the reactions involved in obtaining pure alumina from the mineral bauxite which has impurities of iron oxide and silica.
(b) Draw a labelled diagram of the electrolytic tank cell used for the extraction of aluminium from alumina.
OR
(a) What is corrosion of metals? Name one metal which does not corrode and one which corrodes on being kept in atmosphere.
(b) How will you show that the rusting of iron needs oxygen and moisture at the same time?

Answer 1

Hi there,

The chemical reaction involved in the separation of Alumina from alumina bauxite ore having impurities like Silica:

1. Al2O3 + 2 NaOH -----> 2NaAlO2 + H2O

Aluminium oxide reacts with Sodium hydroxide to give Sodium aluminate and water.

2. 2NaAlO2 + H2O -----> Al(OH)2 + NaOH

Sodium aluminate reacts with water to give Aluminium hydroxide and Sodium hydroxide.

3. Al(OH)2 + Heat ----> Al2O3 + H2O

Aluminium hydroxide decomposes to Give Aluminium oxide(pure) and water.

Hope it helps you.

Answer 2

refer to attached pic plz