Sodium azide

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Sodium azide
Sodium azide bottle and sample.jpg
Sodium azide sample
Names
IUPAC name
Sodium azide
Systematic IUPAC name
Sodium azide
Other names
Azium
Sodium trinitride
Smite
Identifiers
Jmol-3D images Image
Properties
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
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
70.5 J/mol K
21.3 kJ/mol
Hazards
Safety data sheet ScienceLab
Flash point 300 °C
Lethal dose or concentration (LD, LC):
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, in inert atmosphere.

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, though not impossible. Here's one person who managed to make it work.

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.[1] Acidified sodium nitrite can also be used.

Sodium hypochlorite diluted solution (aka bleach) can also be used.[2]

References

  1. http://www.bt.cdc.gov/agent/sodiumazide/basics/facts.asp
  2. https://www.ncbi.nlm.nih.gov/m/pubmed/20667654/

Relevant Sciencemadness threads