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AP EAMCET201824 Apr 2018Morning ShiftChemistryGeneral Principles and Processes of Isolation of MetalsActual

The pair of oxides, which can be leached out, when powdered bauxite containing certain impurities is digested with concentrated solution of NaOH at 473-523 ~K temperature and 35-36 bar pressure are

Options

  1. ATiO ₂, SiO ₂
  2. BSiO ₂, Al ₂ O ₃
  3. CSiO ₂, Fe ₂ O ₃
  4. DAl ₂ O ₃, Fe ₂ O ₃

Correct answer

B. SiO ₂, Al ₂ O ₃

Step-by-step solution

Bauxite is the most important ore of aluminium contains only 30-60 % Al ₂ O ₃ , the rest being a mixture of SiO ₂, Fe ₂ O ₃ and TiO ₂ . The powdered bauxite is treated with concentrated solution of NaOH resulting in the dissolution of Al ₂ O ₃ and SiO ₂ while the other oxides ( Fe ₂ O ₃ . and TiO ₂ ) being basic remain insoluble in NaOH . Hence, only SiO ₂ and Al ₂ O ₃ leached out.

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