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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 · 2024 · Mains Paper I

Q6(c)(i). Lanthanoid–EDTA formation enthalpy

Question

Discuss the following observation: (i) ΔH° for the formation of [Ln(EDTA)(OH₂)ₓ]⁻ (x = 2 or 3) in aqueous solution is nearly constant for all Ln and is almost zero.

Answer in brief

Largely electrostatic Ln–donor bonding and dehydration contributions approximately compensate; favourable entropy can dominate complex formation.

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Topic notes: lanthanides and actinides (lanthanide contraction, magnetic moments, separation), with every Civil Services, IFoS and Geo-Scientist PYQ →

Coverslanthanide EDTA complexesenthalpy of complexationhydrationentropy-driven chelationlanthanoid contraction

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