The brown haze of photochemical smog is largely attributable to (Punjab PMET 2007)

Photochemical smog is initiated by the photochemical dissociation of NO2 that results in the formation of NO. This NO rapidly reacts with O3 [formed by molecular oxygen with O-atoms] to give NO2 [a brown gas], responsible for causing haze, if its concentration is very high. hv 2 NO g NO g O Nascent oxygen very reactive -> 2 3 3 2 2 O O O reacts rapidly with NO O NO NO O Brown gas in high concentration from haze -> ->