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Silver azide

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Silver azide
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.034.173 Edit this at Wikidata
  • InChI=1S/Ag.N3/c;1-3-2/q+1;-1 checkY
    Key: QBFXQJXHEPIJKW-UHFFFAOYSA-N checkY
  • InChI=1/Ag.N3/c;1-3-2/q+1;-1
    Key: QBFXQJXHEPIJKW-UHFFFAOYAJ
  • InChI=1S/Ag.N3/c;1-3-2/q+1;-1
    Key: QBFXQJXHEPIJKW-UHFFFAOYSA-N
  • [Ag+].[N-]=[N+]=[N-]
Properties
AgN3
Molar mass 149.888 g/mol
Appearance colorless solid
Density 4.42 g/cm3, solid
Melting point 250 °C, explosive
Boiling point decomp.
Solubility in other solvents 2.0×10-8 g/L
Structure
Orthorhombic oI16[1]
Ibam, No 72
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
Very toxic, explosive
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 0: Will not burn. E.g. waterInstability 4: Readily capable of detonation or explosive decomposition at normal temperatures and pressures. E.g. nitroglycerinSpecial hazards (white): no code
3
0
4
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

Silver azide is the chemical compound with the formula AgN3. This colorless solid is a well-known explosive.

Structure and chemistry

Silver azide can be prepared by treating an aqueous solution of silver nitrate with sodium azide.[2] The silver azide precipitates as a white solid, leaving sodium nitrate in solution.

AgNO
3
(aq) + NaN
3
(aq) → AgN
3
(s) + NaNO
3
(aq)

X-ray crystallography shows that AgN3 is a coordination polymer with square planar Ag+ coordinated by four azide ligands. Correspondingly, each end of each azide ligand is connected to a pair of Ag+ centers. The structure consists of two-dimensional AgN3 layers stacked one on top of the other, with weaker Ag–N bonds between layers. The coordination of Ag+ can alternatively be described as highly distorted 4 + 2 octahedral, the two more distant nitrogen atoms being part of the layers above and below.[3]

Part of a layer
Layer stacking
4 + 2 coordination of Ag+
2 + 1 coordination of N in N
3

In its most characteristic reaction, the solid decomposes explosively, releasing nitrogen gas:

2 AgN
3
(s) → 3 N
2
(g) + 2 Ag (s)

The first step in this decomposition is the production of free electrons and azide radicals; thus the reaction rate is increased by the addition of semiconducting oxides.[4] Pure silver azide explodes at 340 °C, but the presence of impurities lowers this down to 270 °C.[5] This reaction has a lower activation energy and initial delay than the corresponding decomposition of lead azide.[6]

Safety

AgN3, like most heavy metal azides, is dangerously explosive. Decomposition can be triggered by exposure to ultraviolet light or by impact.[2] Ceric ammonium nitrate is used as an oxidising agent to destroy AgN
3
in spills.[5]

See also

References

  1. ^ Marr H.E. III., Stanford R.H. Jr. (1962). "The unit-cell dimensions of silver azide". Acta Crystallographica. 15 (12): 1313–1314. doi:10.1107/S0365110X62003497.
  2. ^ a b Jacqueline Akhavan (2004). The chemistry of explosives (2nd ed.). Royal Society of Chemistry. pp. 30–31. ISBN 0854046402.
  3. ^ Schmidt, C. L. Dinnebier, R.; Wedig, U.; Jansen, M. (2007). "Crystal Structure and Chemical Bonding of the High-Temperature Phase of AgN3". Inorganic Chemistry. 46 (3): 907–916. doi:10.1021/ic061963n. PMID 17257034.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  4. ^ Andrew Knox Galwey; Michael E. Brown (1999). Thermal decomposition of ionic solids (vol.86 of Studies in physical and theoretical chemistry. Elsevier. p. 335. ISBN 0444824375.
  5. ^ a b Margaret-Ann Armour (2003). Hazardous laboratory chemicals disposal guide, Environmental Chemistry and Toxicology (3rd ed.). CRC Press. p. 452. ISBN 1566705673.
  6. ^ Jehuda Yinon; Shmuel Zitrin (1996). Modern Methods and Applications in Analysis of Explosives. John Wiley and Sons. pp. 15–16. ISBN 0471965626.