The+Origins+of+Acid+Rain

Oxides of Sulfur: Sulfur occurs naturally in volcanoe and small quantities are found in coal deposits. When these are burnt the sulfur reacts to produce sulfur dioxide

S(s) + O2 (g) > SO2 (g)

In the presence of sunlight and the oxygen in the atmospher further oxidation can take place giving sulfur trioxide.

SO2(g) + 1/2 O2 (g) > SO3 (g)

When this dissolves in rain water in the atmosphere the result is sulfuric acid

SO3(g) + H2O(l)> H2SO4(aq)

Oxides of nitrogen: Although there occur naturally during thunder storms they are mainly produced during the burning of petrol

N2(g) + O2(g)->2NO(g)

Nitrogen dioxide is then formed by further oxidation in the pressence of sunlight in the atmosphere

2NO(g) + O2(g)--->2NO2(g)

When this dissolves in rain water in the pressence of more atmospheric oxygen the result is nitirc acid

4NO2(g) + O2(g) + H2O(l)> 4HNO3(aq)