Photochemical smog occurs in a dry, sunny climate. Its components are PAN, acrolein, ozone, formaldehyde, nitric oxide. It is oxidizing in nature.It is formed as a result of the reaction of sunlight with hydrocarbons and nitrogen oxides. The reactions involved during formation of photochemical smog are shown in the attached image.................(i)Oxygen atoms are very reactive and combine with the dioxygen to produce ozone........................(ii)It rapidly reacts with NO, formed in the first reaction and regenerate (g)Both and ozone are oxidising in nature so they react with the unburnt hydrocarbon in the air to form PAN, formaldehyde and acrolein.