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UPSC Combined Geo-Scientist

Chemist

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

Mains Paper I covers inorganic chemistry.

UPSC Combined Geo-Scientist, Mains · 2025 · Mains Paper I

Q10(b). Masking and demasking in EDTA titrations

Question

Explain masking and demasking with a suitable example with particular reference to complexometric EDTA-based titration.

Answer in brief

Masking converts an interfering ion, without separating it, into a form that does not react with EDTA or the indicator; demasking releases the masked ion later so that it can be titrated.

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Topic notes: EDTA titrations, metal-ion indicators and masking, with every Civil Services, IFoS and Geo-Scientist PYQ →

Coversmasking agentsdemaskingEDTA titrationpotassium cyanide maskingformaldehyde demaskingtriethanolamine

All parts of Question 10