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In the extraction of Aluminium, the silica impurity is removed by 

Chemistry
JAMB 2024

In the extraction of Aluminium, the silica impurity is removed by 

  • A. electrolysis
  • B. filtration
  • C. reaction with H\(_2\)SO\(_4\)
  • D. precipitation
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Correct Answer: Option B
Explanation

Aluminum is extracted from bauxite by electrolysis. The extraction proceeds in two stages;

1. Purification of the Bauxite: The impure bauxite is heated with sodium hydroxide solution to form soluble sodium tetrahydroxy aluminate (iii). The impurities in the ore which are iron (iii) oxide and trioxosilicate (iv) compounds are not soluble in the alkali. They are therefore filtered off as a sludge. 

Aluminum hydroxide crystals is then added to filtrate, NaAl(OH)\(_4\) solution to induce the precipitation of Aluminum hydroxide.

2. The electrolysis of the pure alumina

There is an explanation video available below.


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Explanation Video

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