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Indian Forest Service (Mains)

Chemistry optional

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

Paper I covers physical and inorganic chemistry.

Indian Forest Service (Mains), Chemistry optional · 2025 · Paper I

Q5(c). Hexaamminechromium(III)

Question

Explain the bonding, geometry and magnetic behaviour of [Cr(NH₃)₆]Cl₃ using valence bond theory.

Answer in brief

The complex ion is octahedral, inner-orbital d²sp³, with three unpaired electrons and spin-only moment 3.87 μB.

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The full model answer

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Topic notes: Werner theory, isomerism, IUPAC names and valence bond theory of complexes, with every Civil Services, IFoS and Geo-Scientist PYQ →

Coversvalence bond theory[Cr(NH₃)₆]³⁺d²sp³ hybridisationinner orbital complexspin-only magnetic moment

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