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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3mt040

Select the correct statement(s) about froth flotation of sulphide ores.

  1. AHaematite, being an oxide of a dense metal, is best concentrated by froth flotation with xanthates
  2. BSodium cyanide can be added as a depressant to separate from in an ore containing both
  3. CThe mineral particles are wetted by the oil and are carried to the surface by air bubbles, whereas the gangue is wetted by water and sinks
  4. DSodium ethyl xanthate acts as a depressant, preventing sulphide particles from entering the froth

Answer: B, C

NaCN forms a soluble cyano complex with ZnS surface, so ZnS stays in the pulp while PbS floats (true). Xanthates are collectors, not depressants, so the second statement is false. The third is the basic principle of flotation and is true. Haematite is an oxide ore, concentrated by gravity or magnetic methods, so the last statement is false.
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