Q25 / 160 · AP EAMCET 2018 (23 Apr Shift 1) · Chemistry

The ore which is concentrated by leaching

  • A
    $\mathrm{PbS}$
  • Correct answer
    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

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. $$ \mathrm{Al}_2 \mathrm{O}_3+6 \mathrm{NaOH} \longrightarrow 2 \mathrm{Na}_3 \mathrm{AlO}_3+3 \mathrm{H}_2 \mathrm{O} $$

Hence, the correct answer is option: 'B'.

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