Acid Rain

Essay by emja September 2009

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Acid rain as the name suggests is rain that is acidic, the term isused to describe rain with a pH below 5, before the industrialrevolution rain had a typical pH of 5 to 6 this was before theincrease in air pollution brought about by the burning of fossilfuels, that are burned in factories, vehicles and power stations.

The term “acid rain” was first used over a hundred years ago by theBritish chemist Robert Angus Smith. When he realized that the smokefrom human activity could change the acidity of precipitation, despitethis it was not until the 1950’s that concern was raised about theenvironmental effect and even then this situation was allowed tocontinue to rise until it reached crisis proportions in the late1970’sThe only forms of air pollution were caused by geological events forexample volcano eruptions, lightning and bacterial action in soilsetc.

The increase of certain gasses in the air, sulphur dioxide, carbondioxide, methane, halocarbons and nitrogen oxides being the main ones,leads to them being absorbed into it the water vapour that is presentin the atmosphere at high altitudes this reaction is increased by theenergy from sun light, As the sulphur dioxide and nitrogen oxidesreact with the water vapour, oxygen and other oxidants a mild solutionof sulphuric acid and nitric acid are formed.

This weak acid vapourcan now precipitate into clouds and fall as acid rain, acid snow andeven acidic fog.

Global warming is another problem thatChemistry of acid rain.rainwater is slightly acidic.

Co2+H2OÃ H2CO3H2CO3Ã H++HCO3Carbon dioxide can dissolve in water, some of which forms carbonicacid. Carbonic acid releases H+ making the water slightly acidic.

.Burning sulphur releases SO2.

2S+O2Ã 2SO2Sulphur in coal released as sulphur dioxide.

.sulphur dioxide acidifies water slightly.

SO2+H2OÃ H2SO3H2SO3Ã H++HSO3Sulphur dioxide can dissolve in water, some of which forms sulphurousacid, which releases H+ making the water slightly acidic.

.oxidation of sulphur dioxide...