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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 · 2022 · Paper I

Q5(e). Fluorosulfuric acid and magic acid

Question

Write an equation to show self-ionization of fluorosulphuric acid. What happens when it is mixed with SbF₅? Write the equation. By which name is the mixture known and why? How does the mixture react with Me₃CH?

Answer in brief

HSO₃F/SbF₅ is magic acid; the Lewis acid binds the fluorosulfate base, greatly enhancing protonating power, and isobutane can give a tert-butyl cation with hydrogen evolution.

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The full model answer

As written for the answer booklet: the diagram carries the working, the lines stay short. Read here only; it is not offered as a download.

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Topic notes: non-aqueous solvents: liquid ammonia, HF, sulfuric acid, SO₂, BrF₃ and superacids, with every Civil Services, IFoS and Geo-Scientist PYQ →

Coversfluorosulphuric acidmagic acidsuperacidSbF5tert-butyl cationself-ionisation

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