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 SO_2 into SO_3.

Oxidation of sulphur dioxide into sulphur trioxide in the absence of a

1.	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 SO_2 into SO_3.
Answer» Solution :The oxidation of SULPHUR DIOXIDE into sulphur trioxide can occur both photochemically or non-photochemically. In the NEAR ULTRAVIOLET region, the `SO_2` molecules react `O_3` photochemically. `SO_2 + O_3 overset(hv)to SO_3 +O_2` `2SO_2 + O_2 overset(hv)to 2SO_3` Non-photochemically, `SO_2` may be oxidised by molecular oxygen in presence of dust and soot particles. `2SO_2 + O_2 overset("Particulates")to 2SO_3`