7. Compounds of Xenon

COMPOUNDS OF XENON

Xenon–FLUORINE compounds :

All fluorides of xenon are white solids. They are volatile, readily subliming at room temperature   (298 K)

They can be stored indefinitely in nickel or monel metal containers.

Xenon difluoride

 Xe + F₂   (2 : 1 mixture)      XeF₂ .

It is soluble in water, giving solution 0.15 M at 0ºC. The solution which have pungent smell due to XeF₂ are powerful oxidizing agents.

XeF₂(aq) + 2H⁺ + 2e^–  ® Xe + 2HF(aq) ; Eº = + 2.64 V

 XeF₂ + H₂ ®2 HF + Xe

Hydrolysis is slow in water due to dissolution of XeF₂ in HF formed, but is rapid in basic solution.

2Xe F₂ + 2H₂O ®2 Xe + 4HF + O₂ 

XeF₂ + 2OH^– ® Xe + O₂ + 2F^– + H₂O

It acts as fluoride ion donor  XeF₂ (Lewis base) + PF₅ (Lewis acid)  [XeF]⁺ [PF6]^– 

Xenon tetrafluoride

Xe + 2F₂ (1 : 5 mixture)  XeF₄ 

XeF₄ reacts violently with water, giving dangerously explosive XeO₃.

6XeF₄ + 12H₂O  ® 4Xe + 2 XeO₃ + 24 HF + 3O₂ 

XeF₄ can act as F– acceptor as well as F– donors and thus form anionic species in reactions such as :

XeF₄ + NaF ® Na⁺ XeF₅^–

XeF₄ + SbF₅ ® [XeF₃]+ [SbF₆]^– 

Xenon hexafluoride

Xe + 3F₂ (1 : 20 mixture)   XeF₆                

XeF₄ + O₂ F₂ ®  XeF₆ + O₂ 

XeF₆ reacts violently with water but slow hydrolysis with atmospheric moisture giving XeO₃.

XeF₆ + 6 H₂O  ® XeO₃ + 6HF (complete hydrolysis)

With small quantities of water, partial hydrolysis takes place.

XeF₆ + H₂O ®  XeOF₄ (colourless liquid) + 2HF

XeF₆ + 2 H₂O ® XeO₂F₂ + 4HF

XeF₆ reacts with fluoride ion donors to form fluoroanions.

XeF₆ + MF®  M⁺ [XeF₇]^–   (M = Na, K, Rb or Cs)

Xenon–oxygen compounds :

Hydrolysis of XeF₄ and XeF₆ with water gives XeO₃.

6 XeF₄ + 12 H₂O  ® 4 Xe + 2 XeO₃ + 24 HF + 3 O₂

XeF₆ + 3 H₂O ® XeO₃ + 6 HF

Partial hydrolysis of XeF₆ gives oxyfluorides, XeOF₄ and XeO₂F₂ .

XeF₆ + H₂O  ®XeOF₄ + 2 HF   

XeF₆ + 2 H₂O ®  XeO₂F₂ + 4 HF

XeO₃ is a colourless explosive solid and has a pyramidal molecular structure. XeOF₄ is a colourless volatile liquid and has a square pyramidal molecular structure.

Uses :

Helium is a non–inflammable and light gas. Hence, it is used in filling balloons for meteorological observations. It is also used in gas–cooled nuclear reactors. Liquid helium (b.p.4.2 K) finds use as  cryogenic agent for carrying out various experiments at low temperatures. It is used to produce and sustain powerful superconducting magnets which form an essential part of modern NMR spectrometers and Magnetic Resonance Imaging (MRI) systems for clinical diagnosis. It is used as a diluent for oxygen in modern  diving apparatus because of its very low solubility in blood.

Neon is used in discharge tubes and fluorescent bulbs for advertisement display purposes. Neon bulbs are used in botanical gardens and in green houses.

Argon is used mainly to provide an inert atmosphere in high temperature metallurgical processes (arc welding of metals or alloys) and for filling electric bulbs. It is also used in the laboratory for handlsing substances that are air–sensitive.

Xenon and Krypton are used in light bulbs designed for special purposes