UPSC Civil Services (Mains), Chemistry optional · 2022 · Paper I

Q6(d). Separating XeF₆; diborane with NH₃ and with Me₃N

10 marks
Topic: Main group chemistry
Answered

Question

(i) How can XeF₆ be separated from a mixture of XeF₂, XeF₄ and XeF₆? (ii) Write the products with explanation: B₂H₆ + 2NH₃ → ?; B₂H₆ + 2Me₃N → ?

Answer in brief

(i) Pass the vapour over NaF: only XeF₆ is held, as Na₂[XeF₈], and heating gives it back. (ii) B₂H₆ + 2NH₃ → [BH₂(NH₃)₂]⁺[BH₄]⁻; B₂H₆ + 2Me₃N → 2Me₃N·BH₃.

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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 hexafluorideNa2XeF8diborane cleavagediammoniate of diboranesymmetrical cleavageamine–borane adduct

All parts of Question 6

6(a) Metal–metal bonds in Cp₂Fe₂(CO)₄; structure of Bi₅³⁺10 marks
6(b) Pale colours and line-like spectra of lanthanide ions10 marks
6(c) Neutral mixed sandwich compound of a d⁶ centre10 marks
6(d) Separating XeF₆; diborane with NH₃ and with Me₃N10 marks
6(e) Origin of the yellow colour of aqueous FeCl₃10 marks