Nitrogen dioxide
Nitrogen dioxide is a chemical compound with the formula NO
2. It is one of several nitrogen oxides. NO
2 is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year for use primarily in the production of fertilizers. At higher temperatures it is a reddish-brown gas. It can be fatal if inhaled in large quantity.[8] Nitrogen dioxide is a paramagnetic, bent molecule with C2v point group symmetry.
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![]() NO 2 converts to the colorless dinitrogen tetroxide (N 2O 4) at low temperatures and reverts to NO 2 at higher temperatures. | |||
Names | |||
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IUPAC name
Nitrogen dioxide | |||
Other names
Nitrogen(IV) oxide,[1] deutoxide of nitrogen | |||
Identifiers | |||
3D model (JSmol) |
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ChEBI | |||
ChemSpider | |||
ECHA InfoCard | 100.030.234 | ||
EC Number |
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976 | |||
PubChem CID |
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RTECS number |
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UNII | |||
UN number | 1067 | ||
CompTox Dashboard (EPA) |
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Properties | |||
NO• 2 | |||
Molar mass | 46.006 g/mol[2] | ||
Appearance | Brown gas[2] | ||
Odor | Chlorine-like | ||
Density | 1.880 g/L[2] | ||
Melting point | −9.3 °C (15.3 °F; 263.8 K)[2] | ||
Boiling point | 21.15 °C (70.07 °F; 294.30 K)[2] | ||
Hydrolyses | |||
Solubility | Soluble in CCl 4, nitric acid,[3] chloroform | ||
Vapor pressure | 98.80 kPa (at 20 °C) | ||
+150.0·10−6 cm3/mol[4] | |||
Refractive index (nD) |
1.449 (at 20 °C) | ||
Structure | |||
C2v | |||
Bent | |||
Thermochemistry[5] | |||
Heat capacity (C) |
37.2 J/(mol·K) | ||
Std molar entropy (S |
240.1 J/(mol·K) | ||
Std enthalpy of formation (ΔfH⦵298) |
+33.2 kJ/mol | ||
Hazards | |||
Occupational safety and health (OHS/OSH): | |||
Main hazards |
Poison, oxidizer | ||
GHS labelling: | |||
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Danger | |||
H270, H314, H330 | |||
P220, P260, P280, P284, P305+P351+P338, P310 | |||
NFPA 704 (fire diamond) | |||
Lethal dose or concentration (LD, LC): | |||
LC50 (median concentration) |
30 ppm (guinea pig, 1 h) 315 ppm (rabbit, 15 min) 68 ppm (rat, 4 h) 138 ppm (rat, 30 min) 1000 ppm (mouse, 10 min)[6] | ||
LCLo (lowest published) |
64 ppm (dog, 8 h) 64 ppm (monkey, 8 h)[6] | ||
NIOSH (US health exposure limits): | |||
PEL (Permissible) |
C 5 ppm (9 mg/m3)[7] | ||
REL (Recommended) |
ST 1 ppm (1.8 mg/m3)[7] | ||
IDLH (Immediate danger) |
13 ppm[7] | ||
Safety data sheet (SDS) | ICSC 0930 | ||
Related compounds | |||
Related nitrogen oxides |
Dinitrogen pentoxide Dinitrogen tetroxide | ||
Related compounds |
Chlorine dioxide Carbon dioxide | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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It is included in the NOx family of atmospheric pollutants.