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JAMB Chemistry 1986 Question 36

Question 36

Metals and their Compounds

The Iron (III) oxide impurity in bauxite can be removed by

  1. A.fractional crystallization in acid solution
  2. B.dissolution in sodium hydroxide and filtration
  3. C.extraction with concentrated ammonia and reprecipitation
  4. D.electrolysis of molten mixture
Show the answer and explanation

Answer: B (dissolution in sodium hydroxide and filtration)

Explanation

Aluminium oxide is amphoteric and dissolves in hot NaOH, but iron (III) oxide does not. The iron oxide is then filtered off.