Question

Correct statements about oxidising smog are I. \[ \text{Primary precursors of it are } O_3,\ PAN \] II. It occurs in warm, dry and sunny climate III. Its formation can be controlled by the use of catalytic converters in automobiles

• A. II, III only
• B. I, II only
• C. I, III only
• D. I, II, III

Hint:

Photochemical (oxidising) smog: \[ \text{Primary pollutants} = NO_x + \text{Hydrocarbons} \] \[ \text{Secondary pollutants} = O_3,\ PAN,\ Aldehydes \] It is commonly called Los Angeles smog and forms on sunny days.

Answer 1

The Correct Option is A

Statement I: Photochemical (oxidising) smog is formed from the primary pollutants \[ NO_x \] and \[ \text{hydrocarbons (VOCs)}. \] The compounds \[ O_3 \] and \[ PAN \] are formed during the reaction process and are therefore

secondary pollutants, not primary precursors. \[ \boxed{\text{Statement I is incorrect}} \]

Statement II: Photochemical smog forms due to sunlight-driven reactions involving nitrogen oxides and hydrocarbons. Hence it is commonly observed in \[ \text{warm, dry and sunny climates}. \] \[ \boxed{\text{Statement II is correct}} \]

Statement III: Catalytic converters reduce emissions of \[ NO_x, \] carbon monoxide and hydrocarbons from automobiles. Since these pollutants are responsible for photochemical smog formation, catalytic converters help control it. \[ \boxed{\text{Statement III is correct}} \]

Final Result: Only statements II and III are correct. \[ \boxed{\text{II, III only}} \] \[ \boxed{\text{Answer = (A)}} \]