Question

From where does ozone come in the photochemical smog?

Answer 1

NO₂ absorbs energy from sunlight and breaks up into nitric oxide and free oxygen atom and this can be shown as- 

\[\ce{NO2 (g) ->[hv] NO (g) + O (g)}\]

Here the oxygen atom produced is very reactive and combines with oxygen molecule in the air to give rise to ozone. 

\[\ce{O (g) + O2 (g) + M -> O3 (g) + M}\]

Here ‘M’ is an inert gas like Nitrogen gas and ozone gets produced during the formation of smog.