Silver oxide

From Wikipedia, the free encyclopedia
  (Redirected from Silver(I) oxide)
Jump to: navigation, search
Not to be confused with silver(I,III) oxide, used in silver-oxide batteries.
Silver oxide
Silver oxide.jpg
Identifiers
CAS number 20667-12-3 YesY
RTECS number VW4900000
Properties
Molecular formula Ag2O
Molar mass 231.735 g/mol
Appearance black/brown cubic crystals
Density 7.14 g/cm3
Melting point 280 °C (536 °F; 553 K) (decomposition)
Solubility in water 0.025 g/L[1]
Solubility product, Ksp of AgOH 1.52×10−8 (20 °C)
Solubility soluble in acid, alkali
insoluble in alcohol, ethanol[1]
Structure
Crystal structure cubic
Thermochemistry
Specific
heat capacity
C
65.9 J·mol−1·K−1[2]
Std molar
entropy
So298
122 J·mol−1·K−1[3]
Std enthalpy of
formation
ΔfHo298
−31 kJ·mol−1[3]
Related compounds
Related compounds silver(I,III) oxide, AgO
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 YesY (verify) (what is: YesY/N?)
Infobox references

Silver(I) 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[edit]

Silver oxide can be prepared by combining aqueous solutions of silver nitrate and an alkali hydroxide.[4] This reaction does not afford appreciable amounts of silver hydroxide due to the favorable energetics for the following reaction:[5]

2 AgOH → Ag2O + H2O (pK = 2.875[6])

Structure and properties[edit]

Ag2O structure

Ag2O is isostructural with Cu2O. It is therefore expected that Ag2O is insoluble in all solvents,[7] except by reaction. It is slightly soluble in water due to the formation of the ion Ag(OH)2 and possibly related hydrolysis products.[8] It dissolves in ammonia solution to give soluble derivatives.[citation needed]

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.[9][8]

Like many silver compounds, silver oxide is photosensitive. It also decomposes at temperatures above 280 °C.[7]

Applications[edit]

This oxide is used in some silver-oxide batteries, as is the peroxide, Ag4O4. In organic chemistry, silver oxide is used as a mild oxidizing agent. For example, it oxidizes aldehydes to carboxylic acids. Such reactions often work best when the silver oxide is prepared in situ from silver nitrate and alkali hydroxide.

References[edit]

  1. ^ a b Lide, David R. (1998). Handbook of Chemistry and Physics (87 ed.). Boca Raton, FL: CRC Press. pp. 4–83. ISBN 0-8493-0594-2. 
  2. ^ Lide, David R. (1998). Handbook of Chemistry and Physics (87 ed.). Boca Raton, FL: CRC Press. pp. 5–5. ISBN 0-8493-0594-2. 
  3. ^ a b Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A23. ISBN 0-618-94690-X. 
  4. ^ Janssen, D. E.; Wilson, C. V. (1963), "4-Iodoveratrole", Org. Synth. ; Coll. Vol. 4: 547 
  5. ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
  6. ^ Biedermann, George; Sillén, Lars Gunnar (1960). "Studies on the Hydrolysis of Metal Ions. Part 30. A Critical Survey of the Solubility Equilibria of Ag2O". Acta Chemica Scandinavica 14: 717. doi:10.3891/acta.chem.scand.14-0717. 
  7. ^ a b Merck Index of Chemicals and Drugs, 14th ed. monograph 8521
  8. ^ a b Cotton, F. Albert; Wilkinson, Geoffrey (1966). Advanced Inorganic Chemistry (2nd Ed.). New York:Interscience. p. 1042. 
  9. ^ General Chemistry by Linus Pauling, 1970 Dover ed. p703-704

External links[edit]