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UPSC Combined Geo-Scientist

Chemist

  • 3 descriptive papers
  • 200 marks each
  • 3 h per paper

Mains Paper III covers analytical and organic chemistry.

UPSC Combined Geo-Scientist, Mains · 2021 · Mains Paper III

Q5(b). Extraction of Pb²⁺ as a chelate: the dithizone method

Question

How will you extract Pb²⁺ ions from its aqueous solution through extraction by chelation technique?

Answer in brief

Shake the solution (pH 8.5–10, ammoniacal citrate and cyanide) with dithizone in CHCl₃: lead passes into the organic layer as the neutral red chelate Pb(HDz)₂.

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The full model answer

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Topic notes: chromatography and solvent extraction (plates, resolution, van Deemter, HPLC, GLC, ion exchange, Craig), with every Civil Services, IFoS and Geo-Scientist PYQ →

Coverschelate extractiondithizonelead extractionsolvent extractionmasking

All parts of Question 5