Sodium azide
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| Names | |
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| Other names
Sodium trinitride
Smite Azium |
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| Identifiers | |
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3D model (Jmol)
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| ChEBI | |
| ChemSpider | |
| ECHA InfoCard | 100.043.487 |
| EC Number | 247-852-1 |
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PubChem CID
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| RTECS number | VY8050000 |
| UN number | 1687 |
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| Properties | |
| NaN3 | |
| Molar mass | 65.0099 g/mol |
| Appearance | colorless to white solid |
| Odor | odorless |
| Density | 1.846 g/cm3 (20 °C) |
| Melting point | 275 °C (527 °F; 548 K) violent decomposition |
| 38.9 g/100 mL (0 °C) 40.8 g/100 mL (20 °C) 55.3 g/100 mL (100 °C) |
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| Solubility | very soluble in ammonia slightly soluble in benzene insoluble in ether, acetone, hexane, chloroform |
| Solubility in methanol | 2.48 g/100 mL (25 °C) |
| Solubility in ethanol | 0.22 g/100 mL (0 °C) |
| Acidity (pKa) | 4.8 |
| Structure | |
| Hexagonal, hR12 | |
| R-3m, No. 166 | |
| Thermochemistry | |
| 76.6 J/mol K | |
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Std molar
entropy (S |
70.5 J/mol K |
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Std enthalpy of
formation (ΔfH |
21.3 kJ/mol |
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Gibbs free energy (ΔfG˚)
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99.4 kJ/mol |
| Hazards | |
| Safety data sheet | External MSDS |
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EU classification (DSD)
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Highly toxic (T+) Very dangerous for the environment (N) |
| R-phrases | R28, R32, R50/53 |
| S-phrases | (S1/2), S28, S45, S60, S61 |
| NFPA 704 | |
| Flash point | 300 °C (572 °F; 573 K) |
| Lethal dose or concentration (LD, LC): | |
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LD50 (median dose)
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27 mg/kg (oral, rats/mice) |
| US health exposure limits (NIOSH): | |
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PEL (Permissible)
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none |
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REL (Recommended)
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C 0.1 ppm (as HN3) [skin] C 0.3 mg/m3 (as NaN3) [skin] |
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IDLH (Immediate danger)
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N.D. |
| Related compounds | |
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Other anions
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Sodium cyanide |
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Other cations
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Potassium azide Ammonium azide |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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 (what is   ?) |
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| Infobox references | |
Sodium azide is the inorganic compound with the formula NaN3. This colorless salt is the gas-forming component in many car airbag systems. It is used for the preparation of other azide compounds. It is an ionic substance, is highly soluble in water, and is very acutely toxic.
Sodium azide is an ionic solid. Two crystalline forms are known, rhombohedral and hexagonal. Both adopt layered structures. The azide anion is very similar in each form, being centrosymmetric with N–N distances of 1.18 Å. The Na+
ion has octahedral geometry. Each azide is linked to six Na+ centers, with three Na-N bonds to each terminal nitrogen center.
The common synthesis method is the "Wislicenus process," which proceeds in two steps from ammonia. In the first step, ammonia is converted to sodium amide:
The sodium amide is subsequently combined with nitrous oxide:
These reactions are the basis of the industrial route, which produced about 250 tons/y in 2004, with production increasing owing to the popularization of airbags.
Curtius and Thiele developed another production process where a nitrite ester is converted to sodium azide using hydrazine. This method is suited for laboratory preparation of sodium azide:
Alternatively the salt can be obtained by the reaction of sodium nitrate with sodium amide.
Treatment of sodium azide with strong acids gives hydrazoic acid, which is also extremely toxic:
Aqueous solutions contain minute amounts of hydrogen azide, the formation of which is described by the following equilibrium:
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