Question

Oxidation of sulphur dioxide into sulphur trioxide in the absence of a catalyst is a slow process but this oxidation occurs easily in the atmosphere. Explain how does this happen. Give chemical reactions for the conversion of SO₂ into SO₃.

Answer 1

The presence of particulate matter in polluted air catalyses the oxidation of SO₂ to SO₃. The reaction is also promoted by ozone and hydrogen peroxide.

\[\ce{2SO2 + O2 ->[Dust or soot particles] 2SO3}\]

\[\ce{SO2 + O3 ->[hv] SO3 + O2}\]

\[\ce{SO2 + H2O2 -> H2O + SO3}\]