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Silver oxide
From Wikipedia, the free encyclopedia
| Silver oxide | |
|---|---|
 |
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| IUPAC name | Silver oxide |
| Other names | Silver rust Argentous oxide |
| Molecular formula | Ag2O |
| Identifiers | |
| CAS number | |
| Properties | |
| Molar mass | 231.7148 g/mol |
| Appearance | black/brown solid |
| Density | 7.2 g/cm3, solid |
| Melting point |
280°C (decomposition) |
| Solubility in water | 0.0013 g/100 ml (20°C) |
| Ksp of AgOH | 1.52 × 10-8 (20°C) |
| Acidity (pKa) | -4 |
| Structure | |
| Crystal structure | cubic |
| Hazards | |
| MSDS | Material Safety Data Sheet |
| Related Compounds | |
| Related compounds | silver(II) oxide, AgO |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references |
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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.
Contents |
Silver oxide is commercially available. It can be easily prepared by combining aqueous solutions of silver nitrate and an alkali hydroxide.[1] Noteworthy is the fact that this reaction does not afford appreciable amounts of silver hydroxide due to the favorable energetics for the following reaction:[2]
- 2 AgOH → Ag2O + H2O K is large
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,[3] 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.[4] 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 + H2O
where 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.[5][4]
Like many silver compounds, silver oxide is photosensitive. It also decomposes at temperatures above 200 °C.[3]
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.[6]
- ^ 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
- ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
- ^ a b Merck Index of Chemicals and Drugs, 9th ed. monograph 8265
- ^ a b Cotton, F. Albert; Wilkinson, Geoffrey (1966). Advanced Inorganic Chemistry (2nd Ed.). New York:Interscience. Advanced Inorganic Chemistry by Cotton and Wilkinson, 2nd ed. p1042
- ^ General Chemistry by Linus Pauling, 1970 Dover ed. p703-704
- ^ 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
- silver(II) oxide, AgO
- Annealing of Silver Oxide Demonstration experiment: Instruction and video
- Silver Oxide, Ag2O