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Which of the following ore is best concentrated by froth-flotation method?
  1. Galena
  2. Cassiterite
  3. Magnetite
  4. Malachite
Solution (A)
Here Galena is Description: 52731.png (a sulphide ore).
Cassiterite is Description: 52739.png (oxide ore). Magnetite is Description: 52747.png (oxide ore) and malachite is Description: 52756.png (carbonate ore). The froth-floatation process is used to concentrate sulphide ores, based on preferential wetting properties with froating agent and water.


How is lime stone used in Fe extraction?
  1. Oxidation of Fe ore
  2. Reduction of Fe ore
  3. Formation of slag
  4. Purification of Fe formed
Solution (C)
Lime stone Description: 52764.png is used for the formation of slag in Fe extraction:
Description: 52772.png
Description: 52793.png


Zone refining is a method to obtain:
  1. very high temperature
  2. ultra pure Al
  3. ultra pure metals
  4. ultra pure oxides
Solution (C)
Zone refining is employed for preparing extremely pure metals.
It is based on the principle that when a molten solution of the impure metal is allowed to cool, the pure metal crystallizes out while the impurities remain in the melt. Semiconductors such as Si, Ge, and Ga are purified by this method.


Gold is extracted by hydrometallurgical process based on its property:
  1. of being electropositive
  2. of being less reactive
  3. to form complexes which are water soluble
  4. to form salts which are water soluble
Solution (C)
Hydrometallurgy is the process of dissolving the metal or its ore by the action of a suitable chemical regent followed by recovery of the metal either by electrolysis or by the use of a suitable precipitating agent.
Description: 52804.png
Description: 52819.png


Pb and Sn are extracted, respectively, from their chief ore by:
  1. carbon reduction and self-reduction
  2. self-reduction and carbon reduction
  3. electrolysis and self-reduction
  4. self-reduction and electrolysis
Solution (B)
Description: 52828.png and Description: 52835.png get reduced by PbS itself which is already present in the mixture. Because the reduction took place by mixture itself, hence is known as self-reduction.
Description: 52845.png
Description: 52856.png

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