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    Toughest Shift of JEE Mains 2026 Till Now: January & April Session Shift-Wise Difficulty Analysis

    Leaching Process - Practice Questions & MCQ

    Edited By admin | Updated on Sep 18, 2023 18:35 AM | #JEE Main

    Quick Facts

    • Leaching: Chemical Method is considered one of the most asked concept.

    • 19 Questions around this concept.

    Solve by difficulty

    The methods NOT involved in concentration of ore are
    A. Liquation
    B. Leaching
    C. Electrolysis
    D. Hydraulic washing
    E. Froth floatation
    Choose the correct answer from the options given below :

    Which of the following metals can be extracted through alkali leaching technique?

    Leaching is often used in the metallurgy of 

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    In extraction of alumina by serper's process the main impurity is 

    Extraction of gold and silver involves leaching the metal with CN- ion. The metal is recovered by ________________.

    Concepts Covered - 0

    Leaching: Chemical Method

    In this method, the powdered ore is treated with a suitable chemical reagent which dissolves the ore while impurities remain insoluble in that reagent.
    For example: 
    Bauxite is separated from Fe2O3, SiO2, TiO2, with the help of NaOH in which Al2O3 gets dissolved while rest are insoluble.
    For example:

    \mathrm{Al}_{2} \mathrm{O}_{3}(\mathrm{s})+2 \mathrm{NaOH}(\mathrm{aq})+3 \mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \rightarrow 2 \mathrm{Na}\left[\mathrm{Al(OH)}_{4}\right](\mathrm{aq})
    The sodium aluminate present in solution is neutralised by passing CO2 gas and hydrated Al2O3 is precipitated. At this stage, small amount of freshly prepared sample of hydrated Al2O3 is added to the solution. This is called seeding. It induces the precipitation.

    2 \mathrm{Na}\left[\mathrm{Al}(\mathrm{OH})_{4}\right](\mathrm{aq})+\mathrm{CO}_{2}(\mathrm{g}) \rightarrow \mathrm{Al}_{2} \mathrm{O}_{3}.\mathrm{xH}_{2} \mathrm{O}(\mathrm{s})+2 \mathrm{NaHCO}_{3}(\mathrm{aq})

    Sodium silicate remains in the solution and hydrated alumina is filtered, dried and heated to give back pure Al2O3.

    \mathrm{Al}_{2} \mathrm{O}_{3}.\mathrm{xH}_{2} \mathrm{O}(\mathrm{s}) \stackrel{1470 \mathrm{K}}{\longrightarrow} \mathrm{Al}_{2} \mathrm{O}_{3}(\mathrm{s})+\mathrm{xH}_{2} \mathrm{O}(\mathrm{g})

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