Photochemical smog and its production is a reason that is causing wide concern.

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OXFORD CAMBRIDGE AND RSA EXAMINATIONS                

CHEMISTRY (SALTERS)                                                           Lawrence Johnson

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Photochemical smog and its production is a reason that is causing wide concern. It happens when primary pollutants, which are air pollutants that enter the atmosphere directly from things such as motor vehicles, power stations, industry and domestic sources, interact under the influence of sunlight to produce secondary pollutants. Secondary pollutants are therefore atmospheric pollutants that are created chemically when primary pollutants and other components of air react. The main primary pollutants emitted as a result of motor vehicles are Nitrogen oxides (NO×) hydrocarbons(C×Hγ), Carbon Monoxide (CO) and Sulphur oxides (SO×). The main secondary pollutants formed as a result of vehicle emissions are Ozone (O3) and peroxyacetyl nitrate) H O.

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Coal fired power stations are another way in which primary pollutants are emitted into the air and thus contribute to the production of photochemical smog.  This is because the outputs as a result of fuel combustion are things such as NO× gases.

The emission of these nitrogen oxides occurs as flue gases from burning the coal contain oxides of nitrogen.

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In the combustion of coal the nitrogen compounds are oxidised to form the fuel NO×, which is a primary pollutant.

Another way this primary pollutant is formed is when at the high temperatures of combustion, atmospheric nitrogen combines with oxygen to from thermal NO×. Most NO× emissions are thermal so it is this way of Nitrogen combing with oxygen at high temperatures that result in the largest quantities of NO×.

SO× emissions happen in the same sort of way.  As all living organisms contain sulphur in some form when the coal burns in the power station, sulphur compounds are ...

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