Bauxite is the principal ore used in the commercial extraction of aluminium. The Bayer’s process is used to refine bauxite into pure alumina, with caustic soda playing a crucial role in the initial stage of the process. Based on this, answer the following questions:
(a) Explain the reason behind the addition of caustic soda during the Bayer’s process.
(b) Write a balanced chemical equation representing the reaction between bauxite and caustic soda during the Bayer’s process.
Bauxite is the principal ore used in the commercial extraction of aluminium. The Bayer’s process is used to refine bauxite into pure alumina, with caustic soda playing a crucial role in the initial stage of the process. Based on this, answer the following questions:
(a) Explain the reason behind the addition of caustic soda during the Bayer’s process.
(b) Write a balanced chemical equation representing the reaction between bauxite and caustic soda during the Bayer’s process.
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Solution and Explanation
(a) Reason for Caustic Soda: Caustic soda (Sodium Hydroxide) is added because aluminium oxide is amphoteric. It reacts with the hot concentrated alkali to form soluble Sodium Meta-aluminate, while the main impurities in bauxite (like Ferric Oxide) are basic and do not dissolve, allowing them to be filtered out as "red mud."
(b) Balanced Equation: [ Al_2O_3 cdot 2H_2O + 2NaOH 2NaAlO_2 + 3H_2O ] (Bauxite reacts with sodium hydroxide to produce sodium meta-aluminate and water).
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