General Methods of Extraction of Metals

Metallurgy is the process of extracting metals economically from their ores and refining the extracted raw material into purer form. The naturally occurring compounds of metals that are found in earth’s crust along with some impurities are called minerals. An ore is the mineral from which the metal can be extracted profitably and conveniently. The impurity associated with the minerals is called Gangue or matrix. Flux is the substance added to the ore to remove the gangue resulting in the formation of a fusible mass known as slag. The process of metallurgy involves several steps like crushing and grinding of ore, concentration of ore, extraction of metal and finally, refining of metal. The process of removing unwanted impurities like sand, earthly impurities from ore is called concentration of ore or enrichment of ore or ore dressing. Different techniques of concentration of ore are gravity separation, froth floatation, leaching and magnetic separation. Leaching of bauxite ore is done by Baeyer’s Process. Concentrated ore is converted to metal oxide by Calcination and Roasting. Calcination is the process of heating the ore in the absence of air at a temperature insufficient to melt the ore. In roasting, the concentrated ore is heated to a high temperature in excess of air. The metallic oxide obtained either by roasting or by calcination of concentrated ore is reduced to free metal. The metals obtained from the metallurgical process undergo the process of refining through different processes like distillation, liquation, oxidation and electrolytic refining.

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  • Q1

    A substance added to an ore to remove earthy impurities, resulting in the formation of a fusible compound is known as

    Marks:1
    Answer:

    flux.

    Explanation:

    Flux is a substance added to an ore to remove the gangue (earthy impurities) resulting in the formation of a fusible compound (slag).

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  • Q2

    Calamine is an ore of

    Marks:1
    Answer:

    zinc.

    Explanation:

    Calamine is ZnCO3. It is an ore of zinc.

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  • Q3

    Chemical formula of haematite is

    Marks:1
    Answer:

    Fe2O3

    Explanation:

    Haematite is an oxide ore of iron.

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  • Q4

    Cinnabar is sulphide ore of

    Marks:1
    Answer:

    mercury.

    Explanation:

    Cinnabar (HgS) is sulphide ore of mercury.  

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  • Q5

    A metal that occurs in native state is

    Marks:1
    Answer:

    Au

    Explanation:

    The metals that are placed at the bottom of the activity series are least reactive. Hence, they are found in native or free state. E.g., gold and platinum

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