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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 · 2022 · Mains Paper III

Q5(b). Fe(III) left after three extractions with ether

Question

Calculate the weight of Fe(III) left unextracted from a 100 mL aqueous solution having 500 mg of Fe³⁺ ion in 6 N HCl after three extractions with 10 mL of diethyl ether in each go. [Given: The distribution ratio between water and diethyl ether is 150]

Answer in brief

Each extraction leaves 1/16 of the iron in the water; after three extractions 500 × (1/16)³ = 0.122 mg of Fe(III) is left and 99.98 % has been extracted.

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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 →

Coverssolvent extractiondistribution ratiomultiple extractioniron ether extractionfraction unextracted

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