THE OXIDES OF NITROGEN
(By Michael Colgan Y11 Ta Chem)

 

NITROGEN MONOXIDE ( also called nitrogen (ii) oxide or  nitric oxide)
NITROGEN DIOXIDE  (also called nitrogen (iv) oxide or nitrous oxide)  
Their formulae, respectively, are NO and NO₂ 
NO is a colourless gas while NO2 is a brown gas 
(as in the picture above).

Nitrogen oxides are produced above all as unwanted by-products of firing processes at high temperatures (above all in in motor vehicle engines and power stations) and in the chemicals industry (fertiliser production). 

Nitrogen, because of its extremely strong and stable triple covalent bond, is very unreactive. It will only react when the conditions of temperature and pressure are extreme, like in the engine of a car or in the reactor of chemical plant.  These oxides are made as a result of the following chemical reactions under such extreme conditions: - 

N₂ + O₂  =  2NO

N₂  + 2O₂  =  2NO₂

• Nitrogen oxides attack the membranes of the respiratory organs
  and increase the likelihood of respiratory illness.  
  

• Short-term exposures (e.g., less than 3 hours) to low levels of nitrogen dioxide (NO₂)
  may lead to changes in airway responsiveness and lung function in individuals with pre-existing respiratory illnesses. 
  

• Their effects are worse in children (5–12 years old). 
  

• Long term exposures to NO₂ may lead to increased susceptibility to respiratory infection and may cause permanent alterations in the lung.
  

• Nitrogen oxides react in the air to form... 
  ground-level ozone (O₃) and fine particle pollution, 
  which are both associated with adverse health effects.

[Please click here to see our OZONE PAGE.]

The oxides of nitrogen also react with ammonia, moisture, and other compounds to form nitric acid and related particles. Human health concerns include effects on breathing and the respiratory system, damage to lung tissue, and premature death. Small particles penetrate deeply into sensitive parts of the lungs and can cause or worsen respiratory disease such as emphysema and bronchitis, and aggravate existing heart disease

Factories are the main source of nitrogen oxides. The graph below shows how levels of the oxides typically change throughout the working day.

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