• # question_answer 30)   The pollutants which come directly in the air from sources are called primary pollutants. Which of the following belongs to secondary air pollutants? (a) CO                                   (b) Hydrocarbons             (c) Peroxyacetyl nitrate                 (d) No

(c) Hydrocarbons present in atmosphere combine with oxygen atom produced by the photolysis of $N{{O}_{2}}$ to form highly reactive intermediate called free radical. Free radical initiates a series of reactions. Peroxyacyl nitrates are formed, which can be said as secondary pollutant. $RH+O\to {{R}^{\centerdot }}+RC{{O}^{\centerdot }}$ $RC{{O}^{\centerdot }}+{{O}_{2}}\to RCO_{3}^{\centerdot }$ $RCO_{3}^{\centerdot }+N{{O}_{2}}\to \underset{\operatorname{Peroxyacyl}\,nitrate}{\mathop{RC{{O}_{3}}\cdot N{{O}_{2}}}}\,$