Disulfite

From Wikipedia, the free encyclopedia
Not to be confused with Bisulfite.
Disulfite ion
IUPAC name

disulfite [1]

Other names

metabisulfite ion
pyrosulfite

Identifiers
PubChem 159940
Properties
Molecular formula S2O5
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

A disulfite, commonly known as metabisulfite, is a chemical compound containing the disulfite ion (metabisulfite ion) [S2O5]2-.

Structure of metabisulfite ion

Chemistry

Production of the disulfite ion

The disulfite ion is a dimer of the bisulfite ion (HSO3−). It can arise from:

Dehydration

In aqueous solution, the disulfite ion is formed in minor amounts by dehydration of bisulfite in an equilibrium:

2 HSO3− (aq) S2O52− (aq) + H2O (l)

Although the equilibrium lies far to the left, evaporation of a bisulfite salt will produce a substantial amount of disulfite.[2]

In fact, disulfite is the ion of disulfurous acid (pyrosulfurous acid), which originates from sulfurous acid in accordance with the dehydration reaction above:

2 H2SO3 → 2 HSO3− + 2 H+ → H2S2O5 + H2O


Addition

The disulfite ion also arises from the addition of sulfur dioxide to the sulfite ion:

HSO3− SO32− + H+

SO32− + SO2 S2O52− 		 

Other reactions

In aqueous solution, disulfite salts decompose with acids:

S2O52− + H+ → HSO3− + SO2

Examples of disulfites

References

  1. ↑ International Union of Pure and Applied Chemistry (2005). Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005). Cambridge (UK): RSC–IUPAC. ISBN 0-85404-438-8. p. 130. Electronic version.
  2. ↑ Bassam Z. Shakhashiri: Chemical demonstrations: a handbook for teachers of chemistry The University of Wisconsin Press @Google Books, 1992, p.9
This article is issued from Wikipedia. The text is available under the Creative Commons Attribution/Share Alike; additional terms may apply for the media files.