Question

Photochemical smog is _____ in character while classical smog is _____ in character.

Answer 1

Photochemical smog is formed by the action of sunlight on unsaturated hydrocarbons and nitrogen oxides.
Photochemical smog is sometimes called as oxidising smog as it contains high concentration of oxidising agents like ozone, $HN{O}_3$ whereas, classical smog is called reducing smog as it contains high concentration of sulphur dioxide, which is a reducing agent.
Hence, correct option is (a).