Potassium compounds: potassium bromide

potassium symbol icon

The potassium in potassium bromide formally is in the oxidation state 1.

Crystal structure of potassium bromide

Potassium bromide

  • Formula as often written: KBr
  • Hill system formula: Br1K1
  • CAS registry number: [7758-02-3]
  • Formula weight: 119.002
  • Class: bromide

Synonyms

  • potassium bromide
  • potassium(I) bromide

Physical properties

  • Colour: white
  • Appearance: crystalline solid
  • Melting point: 734°C
  • Boiling point: 1435°C
  • Density: 2750 kg m-3

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Element analysis

Element percentages for the elements in potassium bromide
Element %
Br 67.14
K 32.86

Synthesis

One way to make potassium bromide is to react the hydroxide with hydrobromic acid. The resulting salt can then be purified by recrystallization.

KOH(aq) + HBr(aq) → KBr(aq) + H2O(l)

While not a normal route of preparation because of the expense, potassium metal reacts vigorously with all the halogens to form potassium halides. So, it burns with bromine, Br2, to form potassium(I) bromide, KBr.

2K(s) + Br2(g) → 2KBr(s)

Solid state structure

  • Geometry of potassium: 6 coordinate: octahedral
  • Prototypical structure: NaCl (rock salt)

Crystal structure of potassium bromide

Isotope pattern

What follows is the calculated isotope pattern for the KBr unit with the most intense ion set to 100%.

Formula: K1Br1

mass  %
118  95.7 ________________________________________________
119 0.0
120 100.0 __________________________________________________
121 0.0
122 6.7 ___

References

The data on these compounds pages are assembled and adapted from the primary literature and several other sources including the following.

  • R.T. Sanderson in Chemical Periodicity, Reinhold, New York, USA, 1960.
  • N.N. Greenwood and A. Earnshaw in Chemistry of the Elements, 2nd edition, Butterworth, UK, 1997.
  • F.A. Cotton, G. Wilkinson, C.A. Murillo, and M. Bochmann, in Advanced Inorganic Chemistry, John Wiley & Sons, 1999.
  • A.F. Trotman-Dickenson, (ed.) in Comprehensive Inorganic Chemistry, Pergamon, Oxford, UK, 1973.
  • R.W.G. Wyckoff, in Crystal Structures, volume 1, Interscience, John Wiley & Sons, 1963.
  • A.R.West in Basic solid state chemistry Chemistry, John Wiley & Sons, 1999.
  • A.F. Wells in Structural inorganic chemistry, 4th edition, Oxford, UK, 1975.
  • J.D.H. Donnay, (ed.) in Crystal data determinative tables, ACA monograph number 5, American Crystallographic Association, USA, 1963.
  • D.R. Lide, (ed.) in Chemical Rubber Company handbook of chemistry and physics, CRC Press, Boca Raton, Florida, USA, 77th edition, 1996.
  • J.W. Mellor in A comprehensive treatise on inorganic and theoretical chemistry, volumes 1-16, Longmans, London, UK, 1922-1937.
  • J.E. Macintyre (ed.) in Dictionary of inorganic compounds, volumes 1-3, Chapman & Hall, London, UK, 1992.

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potassium atomic number