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Question: Answered & Verified by Expert
The ore which is concentrated by leaching
ChemistryGeneral Principles and Processes of Isolation of MetalsAP EAMCETAP EAMCET 2018 (23 Apr Shift 1)
Options:
  • A $\mathrm{PbS}$
  • B $\mathrm{Al}_2 \mathrm{O}_3 \cdot 2 \mathrm{H}_2 \mathrm{O}$
  • C $\mathrm{SnO}_2$
  • D $\mathrm{Fe}_2 \mathrm{O}_3$
Solution:
2011 Upvotes Verified Answer
The correct answer is: $\mathrm{Al}_2 \mathrm{O}_3 \cdot 2 \mathrm{H}_2 \mathrm{O}$
Leaching is a process in which powdered ore is treated with certain reagents, which dissolves the ore leaving behind impurities in undissolved form. Aluminium ore is concentrated by this method, bauxite $\left(\mathrm{Al}_2 \mathrm{O}_3 \cdot 2 \mathrm{H}_2 \mathrm{O}\right)$ contain ferric oxide, titanium oxide and silica as impurities.
Bauxite is treated with aqueous solution of caustic soda. Alumina get dissolved forming soluble sodium aluminate leaving behind impurities.
$$
\mathrm{Al}_2 \mathrm{O}_3+6 \mathrm{NaOH} \longrightarrow 2 \mathrm{Na}_3 \mathrm{AlO}_3+3 \mathrm{H}_2 \mathrm{O}
$$

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