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UPSC Civil Services (Mains)

Chemistry optional

  • 2 papers
  • 250 marks each
  • 3 h per paper
  • 5 of 8 questions, Q1 and Q5 compulsory

Paper I covers physical and inorganic chemistry.

UPSC Civil Services (Mains), Chemistry optional · 2023 · Paper I

Q5(e). Trans effect: A and B from [PtCl₄]²⁻

Question

Identify A and B in the substitution reaction [PtCl₄]²⁻ + NO₂⁻ → [A], then [A] + NH₃ → [B]. Justify by explaining the kinetic trans effect using polarization theory.

Answer in brief

A = [PtCl₃(NO₂)]²⁻; B = trans-[PtCl₂(NO₂)(NH₃)]⁻, with NH₃ trans to NO₂⁻.

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Topic notes: labile and inert complexes, substitution mechanisms, the trans effect, stability constants and the chelate effect, with every Civil Services, IFoS and Geo-Scientist PYQ →

Coverstrans effectpolarisation theorysquare planar platinum complexesligand substitutioncisplatin synthesis

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