Silver oxide

This article is about silver(I) oxide. For the mixed-valence oxide, see Silver(I,III) oxide.

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.

Silver oxide

Silver(I) oxide structure in unit cell Unit cell
Crystal packing
Silver(I) oxide powder
Names
IUPAC name Silver(I) oxide
Other names Silver rust, Argentous oxide, Silver monoxide
Identifiers
CAS Number	20667-12-3 Y
3D model (JSmol)	Interactive image
ChemSpider	7970393 N
ECHA InfoCard	100.039.946
EC Number	243-957-1
MeSH	silver+oxide
PubChem CID	9794626
RTECS number	VW4900000
UNII	897WUN6G6T Y
CompTox Dashboard (EPA)	DTXSID40893897
InChI InChI=1S/2Ag.O/q2*+1;-2 N Key: NDVLTYZPCACLMA-UHFFFAOYSA-N N InChI=1S/2Ag.O/q2*+1;-2 Key: NDVLTYZPCACLMA-UHFFFAOYSA-N
SMILES [O-2].[Ag+].[Ag+]
Properties
Chemical formula	Ag2O
Molar mass	231.735 g·mol−1
Appearance	Black/ brown cubic crystals
Odor	Odorless[1]
Density	7.14 g/cm3
Melting point	300 °C (572 °F; 573 K) decomposes from ≥200 °C[2][3]
Solubility in water	0.013 g/L (20 °C) 0.025 g/L (25 °C)[4] 0.053 g/L (80 °C)[2]
Solubility product (Ksp) of AgOH	1.52·10−8 (20 °C)
Solubility	Soluble in acid, alkali Insoluble in ethanol[4]
Acidity (pKa)	12.1 (estimated)[5]
Magnetic susceptibility (χ)	−134.0·10−6 cm3/mol
Structure
Crystal structure	Cubic
Space group	Pn3m, 224
Thermochemistry
Heat capacity (C)	65.9 J/mol·K[4]
Std molar entropy (S⦵298)	122 J/mol·K[6]
Std enthalpy of formation (ΔfH⦵298)	−31 kJ/mol[6]
Gibbs free energy (ΔfG⦵)	−11.3 kJ/mol[3]
Hazards
GHS labelling:
Pictograms	[7]
Signal word	Danger
Hazard statements	H272, H315, H319, H335[7]
Precautionary statements	P220, P261, P305+P351+P338[7]
NFPA 704 (fire diamond)	[1] 2 0 1
Lethal dose or concentration (LD, LC):
LD50 (median dose)	2.82 g/kg (rats, oral)[1]
Related compounds
Related compounds	Silver(I,III) oxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Preparation

Silver(I) oxide produced by reacting lithium hydroxide with a very dilute silver nitrate solution

Silver oxide can be prepared by combining aqueous solutions of silver nitrate and an alkali hydroxide.^[8][9] This reaction does not afford appreciable amounts of silver hydroxide due to the favorable energetics for the following reaction:^[10]

2 AgOH → Ag₂O + H₂O    (pK = 2.875^[11])

With suitably controlled conditions, this reaction can be used to prepare Ag₂O powder with properties suitable for several uses including as a fine grained conductive paste filler.^[12]

Structure and properties

Ag₂O features linear, two-coordinate Ag centers linked by tetrahedral oxides. It is isostructural with Cu₂O. It "dissolves" in solvents that degrade it. It is slightly soluble in water due to the formation of the ion Ag(OH)−2 and possibly related hydrolysis products.^[13] It is soluble in ammonia solution, producing active compound of Tollens' reagent. A slurry of Ag₂O is readily attacked by acids:

Ag₂O + 2 HX → 2 AgX + H₂O

where HX = HF, HCl, HBr, HI, or CF₃COOH. It will also react with solutions of alkali chlorides to precipitate silver chloride, leaving a solution of the corresponding alkali hydroxide.^[13][14]

Despite the photosensitivity of many silver compounds, silver oxide is not photosensitive,^[15] although it readily decomposes at temperatures above 280 °C.^[16]

Applications

This oxide is used in silver-oxide batteries.^[17] In organic chemistry, silver oxide is used as a mild oxidizing agent.^[18] For example, it oxidizes aldehydes to carboxylic acids.^[19]