Answer. Combustion of fossil fuels in internal combustion engines, in thermal power stations and factories where huge amount of coal is burnt, NO is formed by the direct combination of nitrogen and oxygen as shown in figure.
N2 + O2 2NO
However, it quickly reacts with air to form nitrogen dioxide. NO is highly toxic gas.
2NO + O2 2NO2
Nitrogen in the air is normally
unreactive
Formation of NO & NO2 on combustion of fossil fuel and causing air
Pollution.
Mixture of these gases represented as NOX enter in the air through automobile exhaust and chimneys of thermal power station
and factories. It irritates breathing passage.