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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 · 2021 · Paper I

Q5(e). Completing five reactions of xenon compounds

Question

Complete the following reactions: (i) XeF₄ + 12 H₂O → ? (ii) XeF₆ + ? → XeOF₄ + PF₅ (iii) XeOF₄ + ? → 2 XeO₂F₂ (iv) 3 XeF₂ + 2 (SO₃)₃ → ? (v) ? + XeF₂ → (C₆H₅)₂SF₂ + Xe

Answer in brief

(i) 6 XeF₄ + 12 H₂O → 4 Xe + 2 XeO₃ + 24 HF + 3 O₂; (ii) POF₃; (iii) XeO₃; (iv) 3 Xe + 3 S₂O₆F₂; (v) (C₆H₅)₂S.

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Topic notes: main group chemistry: boranes, borazine, phosphazenes, silicates, silicones, interhalogens, xenon and sulfur–nitrogen compounds, with every Civil Services, IFoS and Geo-Scientist PYQ →

Coversxenon fluoridesXeF4 hydrolysisXeF2 fluorinating agentnoble gas compoundsVSEPR shapes

All parts of Question 5