Sodium azide

Sodium azide

Sodium azide sample
Names
IUPAC name Sodium azide
Systematic IUPAC name Sodium azide
Other names Azium Sodium trinitride Smite
Identifiers
Jmol-3D images	Image
SMILES [N-]=[N+]=[N-].[Na+]
Properties
Chemical formula	NaN3
Molar mass	65.0099 g/mol
Appearance	White solid
Odor	Odorless
Density	1.846 g/cm3 (20 °C)
Melting point	275 °C (527 °F; 548 K) (violent decomposition)
Boiling point	Violent decomposition
Solubility in water	38.9 g/100 mL (0 °C) 40.8 g/100 mL (20 °C) 55.3 g/100 mL (100 °C)
Solubility	Very soluble in anhydrous ammonia Slightly soluble in benzene Insoluble in acetone, chloroform, diethyl ether, hexane, toluene
Solubility in methanol	2.48 g/100 mL (25 °C)
Solubility in ethanol	0.22 g/100 mL (0 °C)
Acidity (pKa)	4.8
Thermochemistry
Std molar entropy (So298)	70.5 J/mol K
Std enthalpy of formation (ΔfHo298)	21.3 kJ/mol
Hazards
Safety data sheet	ScienceLab
Flash point	300 °C
Lethal dose or concentration (LD, LC):
LD50 (Median dose)	27 mg/kg (oral, rats/mice)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Sodium azide is a sodium salt with the chemical formula NaN₃.

Properties

Chemical

Sodium azide will decompose at temperatures over 300°C to yield nitrogen gas.

2 NaN₃ → 2Na + 3 N₂

In contact with a strong acid will release hydrazoic acid.

NaN₃ + H⁺ → HN₃ + Na⁺

Sodium azide can be destroyed by reacting it with nitrous acid

2 NaN₃ + 2 HNO₂ → 3 N₂ + 2 NO + 2 NaOH

Physical

Sodium azide is a white odorless salt. Sodium azide is soluble in water (40.8 g/100 mL at 20 °C) and ammonia, but insoluble in acetone, ether, chloroform and hexane.

Availability

Sodium azide was used in the first car airbags, as the gas generator. It is usually mixed with either silica and iron(III) oxide so purification is required.

Preparation

Industrially sodium azide is prepared via "Wislicenus process", by reacting sodium amide with nitrous oxide. Sodium amide is prepared by reacting metallic sodium with anhydrous ammonia.

2 Na + 2 NH₃ → 2 NaNH₂ + H₂

2 NaNH₂ + N₂O → NaN₃ + NaOH + NH₃

As this method uses metallic sodium and inert conditions it is expensive for the amateur chemist.

A less complex synthesis involves the reaction of a nitrite ester with hydrazine:

R-ONO + N₂H₄ + NaOH → NaN₃ + R-OH + 2 H₂O

Another method discussed involves the reaction of sodium nitrite with urea under controlled conditions.

Projects

• Generating pure nitrogen gas
• Preparation of pure sodium

Handling

Safety

Sodium azide is extremely toxic. The toxicity of azides is similar that of cyanides, the lethal dose for an adult human is around 0.7 g.

Storage

Sodium azide should be stored in spark-free containers, away from moisture or any acidic vapors.

Disposal

When disposed of, it must never be poured down the drain, as it will react to either copper or lead plumbing to yield hydrazoic acid. Hydrolysis can also occur in aqueous solutions, at certain pH. Sodium azide must be treated with nitrous acid before being discarded. Sodium nitrite can also be used.

References

Relevant Sciencemadness threads

• Sodium Azide
• Sodium nitrate/urea complex
• Sodium azide toxicity