Silver oxide

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IUPACName = Silver oxide
OtherNames = Silver rust Argentous oxide
Formula = Ag₂O
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CASNo = 20667-12-3
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MolarMass = 231.7148 g/mol
MolarMass_notes = Ag = 93.1%, O = 6.9%
Appearance = black/brown solid
Density = 7.2 g/cm³, solid
MeltingPt = 280°CFact|date=February 2008
Melting_notes = decomposition
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Solubility = 0.0013 g/100 ml (20°C)
SolubilityProduct = 1.52 × 10^-8 (20°C)
SolubilityProductAs = AgOH
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ExternalMSDS = [http://physchem.ox.ac.uk/MSDS/SI/silver_oxide.html Material Safety Data Sheet]
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OtherCpds = silver(I,III) oxide, AgO

Silver oxide is the chemical compound with the formula Ag₂O. It is a fine black or dark brown powder that is used to prepare other silver compounds.

Preparation

Silver oxide is commercially available. It can be easily prepared by combining aqueous solutions of silver nitrate and an alkali hydroxide. [This publication gives the preparation of Ag₂O and silver trifluoroacetate: "4-Iodoveratrole" Janssen, D. E.; Wilson, C. V. Organic Syntheses, Collected Volume 4, pp. 547 (1963). http://www.orgsyn.org/orgsyn/pdfs/CV4P0547.pdf] Noteworthy is the fact that this reaction does not afford appreciable amounts of silver hydroxide due to the favorable energetics for the following reaction: [Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.] :2 AgOH → Ag₂O + H₂O K is large

Properties

Like most binary oxides, Ag₂O is a three-dimensional polymer with covalent metal-oxygen bonding. It is therefore expected that Ag₂O is insoluble in all solvents, [http://themerckindex.cambridgesoft.com/TheMerckIndex/default.asp?formgroup=basenp_form_group&dataaction=db&dbname=TheMerckIndex Merck Index of Chemicals and Drugs] , 14th ed. monograph 8521] except by reaction. It is also slightly soluble in aqueous solution due to the formation of the ion, Ag(OH)₂^– and possibly related hydrolysis products.cite book | author=Cotton, F. Albert; Wilkinson, Geoffrey | title=Advanced Inorganic Chemistry (2nd Ed.) | publisher=New York:Interscience | year=1966 Advanced Inorganic Chemistry by Cotton and Wilkinson, 2nd ed. p1042] It hydrolyzes only slightly in water (1 part in 40,000) and dissolves in ammonium hydroxide solution to give soluble derivatives.

A slurry of Ag₂O is readily attacked by acids::Ag₂O + 2 HX → 2 AgX + H₂Owhere HX = HF, HCl, HBr, or HI, HO₂CCF₃. It will also react with solutions of alkali chlorides to precipitate silver chloride, leaving a solution of the corresponding alkali hydroxide.General Chemistry by Linus Pauling, 1970 Dover ed. p703-704]

Like many silver compounds, silver oxide is photosensitive. It also decomposes at temperatures above 280 °C.

Applications

Silver oxide is used in a silver-oxide battery. Silver oxide reacts easily with ligand precursors such as 1,3-disubstituted imidazolium or benzimidazolium salts to generate the corresponding N-heterocyclic carbene complexes. These silver complexes are useful as carbene-transfer agents, easily displacing labile ligands such as cyclooctadiene or acetonitrile. This is a common way of synthesizing transition metal carbene complexes. [Wang, H. M. J.; Lin, I. J. B. "Facile Synthesis of Silver(I)-Carbene Complexes. Useful Carbene Transfer Agents" Organometallics 1998, "17", 972-975. doi|10.1021/om9709704]

References

ee also

*silver(I,III) oxide, AgO

External links

* [http://www.job-stiftung.de/index.php?id=31,163,0,0,1,0 Annealing of Silver Oxide] Demonstration experiment: Instruction and video
* [http://www.saltlakemetals.com/Silver_Oxide.htm Silver Oxide, Ag2O]