ReasoningModerate1 mark
7(ii)
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:
Explain the reason behind the addition of caustic soda during the Bayer's process.
Topic: Metallurgy, ores, extraction and alloys
Previous-year question practice database
Answer
Exam answer
Alumina in bauxite is amphoteric and dissolves in hot concentrated NaOH as soluble sodium meta-aluminate, while impurities such as Fe₂O₃ remain insoluble and can be filtered off.