Difference between revisions of "Nitrogen dioxide" - New World Encyclopedia
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− | == | + | == Oxides of nitrogen == |
* [[Nitryl]] | * [[Nitryl]] | ||
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::NO<sub>2</sub><sup>+</sup> + e<sup>−</sup> → NO<sub>2</sub> | ::NO<sub>2</sub><sup>+</sup> + e<sup>−</sup> → NO<sub>2</sub> | ||
::NO<sub>2</sub> + e<sup>−</sup> → NO<sub>2</sub><sup>−</sup> | ::NO<sub>2</sub> + e<sup>−</sup> → NO<sub>2</sub><sup>−</sup> | ||
− | + | ||
− | * [[ | + | == See also == |
+ | |||
+ | * [[Nitrogen]] | ||
+ | * [[Nitrous oxide]] | ||
+ | * [[Nitric oxide]] | ||
+ | * [[Oxygen]] | ||
+ | |||
+ | == Notes == | ||
+ | <references/> | ||
==References== | ==References== | ||
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==External links== | ==External links== | ||
+ | |||
*[http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc09/icsc0930.htm International Chemical Safety Card 0930] | *[http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc09/icsc0930.htm International Chemical Safety Card 0930] | ||
*[http://www.npi.gov.au/database/substance-info/profiles/67.html National Pollutant Inventory - Oxides of nitrogen fact sheet] | *[http://www.npi.gov.au/database/substance-info/profiles/67.html National Pollutant Inventory - Oxides of nitrogen fact sheet] |
Revision as of 09:38, 25 May 2008
Nitrogen dioxide | |
---|---|
Identifiers | |
CAS number | [ | ]
Properties | |
Molecular formula | NO2 |
Molar mass | 46.0055 |
Appearance | brown gas |
Density | 1443 kg/m³, liquid 3.4 kg/m³, gas at 294.25 K |
Melting point |
-11.2°C (261.95 K) |
Boiling point |
21.1°C (293.25 K) |
Hazards | |
EU classification | Highly toxic (T+) |
NFPA 704 |
|
R-phrases | R26, R34 |
S-phrases | S1/2, S9, S26, S28,S36/37/39, S45 |
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
Nitrogen dioxide is the chemical compound NO2. It is one of the several nitrogen oxides. This reddish-brown gas has a characteristic sharp, biting odor. NO2 is one of the most prominent air pollutants and a poison by inhalation.
Preparation
Nitrogen dioxide (NO2) is prepared by simple reaction of nitric acid (HNO3) over copper metal. The reaction is the following:
- 4HNO3(aq) + Cu(s) → Cu(NO3)2(aq) + 2NO2(g) + 2H2O(L)
Safety and pollution considerations
Nitrogen dioxide is toxic by inhalation. Symptoms of poisoning (lung edema) tend to appear several hours after one has inhaled a low but potentially fatal dose. Also, low concentrations (4 ppm) will anesthetize the nose, thus creating a potential for overexposure.
Long-term exposure to NO2 at concentrations above 40–100 µg/m³ causes adverse health effects[1].
Nitrogen dioxide is formed in most combustion processes using air as the oxidant. At elevated temperatures nitrogen combines with oxygen to form nitrogen dioxide:
- 2O2 + N2 → 2 NO2
The most important sources of NO2 are internal combustion engines [2], thermal power stations and, to a lesser extent, pulp mills.[3]
The map shown below, depicting results of satellite measurements over Europe, illustrates nitrogen dioxide as large scale pollutant, with rural background ground level concentrations in some areas around 30 µg/m³, not far below unhealthful levels. Nitrogen dioxide plays a role in atmospheric chemistry, including the formation of tropospheric ozone. A recent study by researchers at the University of California, San Diego, suggests a link between NO2 levels and Sudden Infant Death Syndrome. [4]
Oxides of nitrogen
- Nitryl
- Nitrous oxide or N2O, "laughing gas", a linear molecule, isoelectronic with CO2 but with a nonsymmetric arrangement of atoms (NNO)
- Nitric oxide or NO, a problematic pollutant that is short lived because it converts to NO2 in the presence of free oxygen.
- NOx = all of the above in unspecified proportions but tending toward NO2.
More esoteric nitrogen oxides include N2O5 and the blue species N2O3.
Oxidized (cationic) and reduced (anionic) derivatives of many of these oxides exist: nitrite (NO2−), nitrate (NO3−), nitronium or NO2+, and nitrosonium or NO+. NO2 is intermediate between nitrite and nitronium:
- NO2+ + e− → NO2
- NO2 + e− → NO2−
See also
Notes
- ↑ Health Aspects of Air Pollution with Particulate Matter,Ozone and Nitrogen Dioxide. Retrieved 2008-02-25.
- ↑ Son, Busoon and Wonho Yang, Patrick Breysse, Taewoong Chung and Youngshin Lee (March 2004). Estimation of occupational and nonoccupational nitrogen dioxide exposure for Korean taxi drivers using a microenvironmental model. Environmental Research 94 (3): 291-296.
- ↑ Air emissions. Botnia. Retrieved 2008-02-25.
- ↑ Sids Linked to Nitrogen Dioxide Pollution. Retrieved 2008-02-25.
ReferencesISBN links support NWE through referral fees
External links
- International Chemical Safety Card 0930
- National Pollutant Inventory - Oxides of nitrogen fact sheet
- NIOSH Pocket Guide to Chemical Hazards
- WHO-Europe reports: Health Aspects of Air Pollution (2003) (PDF) and "Answer to follow-up questions from CAFE (2004) (PDF)
- Nitrogen Dioxide Air Pollution
- Nitrogen dioxide pollution in the world (image)
- Computational Chemistry Wiki
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