Chemical elements
  Boron
    Isotopes
    Energy
    Production
    Application
    Physical properties
    Chemical properties
      Boron Hydrides
      Tetraborodecahydride
      Borobutane
      Hexaborododecahydride
      Borohexylene
      Boron trihydride
      Boro-ethane
      Decaborotetradecahydride
      Boron halogen
      Boron trifluoride
      Hydrofluoboric acid
      Potassium borofluoride
      Fluoboric acid
      Perfluoboric acid
      Boron subchloride
      Boron trichloride
      Boron tribromide
      Boron tri-iodide
      Oxides of Boron
      Tetraboron trioxide
      Boron dioxide
      Tetraboron pentoxide
      Borohydrates
      Hypoborates
      Boron sesqui-oxide
      Boron trioxide
      Boric anhydride
      Boric Acids
      Orthoboric acid
      Boric acid
      Boracic acid
      Complex Boric Acids
      Perboric Acid and Perborates
      Sodium perborate
      Sodium hyperborate
      Potassium perborate
      Rubidium perborate
      Ammonium perborate
      Barium perborate
      Boron sesquisulphide
      Boron trisulphide
      Boron pentasulphide
      Boron selenide
      Boron nitride
      Boron amide
      Boron imide
      Boron phosphide
      Boron phospho-iodides
      Boron carbide
      Boron thiocyanate
      Boron Alkyls
      Boron trimethyl
      Boron Silicides and
      Boroethane

Boron trihydride, B2H6






Boron trihydride or boro-ethane, B2H6 has been mentioned that the compound B4H10 is very unstable. When kept over mercury at the ordinary temperature it decomposes with the formation of a gaseous hydride B2H6 and hydrogen. The rate of decomposition is greatly augmented by ultraviolet light, but not appreciably by sunlight. The change is practically complete at 100° after one hour.

Boron trihydride is a colourless gas possessing a repulsive odour which recalls that of B4H10, and also that of hydrogen sulphide. Its vapour density corresponds with the molecular formula B2H6. The hydride melts at -169° and boils at -87° C. The vapour pressure of the liquid at various temperatures is as follows: -

Temp. °C-130°-120°-112°-110°-100°-90°-87°
Vap. press, (in cms.)41022.425406576


Boron trihydride is fairly stable, but it slowly decomposes even at the ordinary temperature. When heated with a free flame, solid, but not liquid, hydrides are produced; when sparked, boron is deposited and non-volatile hydrides of unpleasant odour are produced. In the presence of air it gives rise to solids containing both boron and oxygen, and when exploded with oxygen it reacts thus: -

B2H6 + 3O2 = B2O3 + 3H2O.

It dissolves in carbon disulphide, and the solution decolorises bromine; it does not react with dry hydrogen chloride, but combines readily with dry ammonia.

Boron trihydride reacts with water to give boric acid and hydrogen: -

B2H6 + 6H2O = 2H3BO3 + 6H2.

Like the hydride B4H10, it gives a hypoborate with alkali hydroxide, but some hydrogen is evolved immediately the gas and. the hydroxide come into contact. The hypoborate slowly decomposes, and the final result may be expressed thus: -

B2H6 + 6NaOH = 2Na3BO3 + 6H2.


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