Answer: NO 2 → NO + O; O + O 2 → O 3 ; O 3 + hydrocarbons → PAN and other irritants.
- A NO<sub>2</sub> → NO + O; O + O<sub>2</sub> → O<sub>3</sub>; O<sub>3</sub> + hydrocarbons → PAN and other irritants
- B Atmospheric CO<sub>2</sub> absorbing sunlight and directly forming smog particles
- C SO<sub>2</sub> reacting with ozone to form the bulk of urban photochemical smog
- D Ammonia reacting with atmospheric water vapour to form smog droplets
Correct answer: A. NO<sub>2</sub> → NO + O; O + O<sub>2</sub> → O<sub>3</sub>; O<sub>3</sub> + hydrocarbons → PAN and other irritants
Explanation: Photochemical smog: sunlight photodissociates NO<sub>2</sub> → NO + O(radical); O reacts with O<sub>2</sub> to give O<sub>3</sub>; O<sub>3</sub> + VOCs produce PAN, aldehydes, and other irritants.
Xenon tetrafluoride (XeF4) has six electron domains around xenon — four Xe–F bonds plus two lone pairs. The lone pairs occupy opposite axial positions, leaving the four fluorine atoms in a square-planar shape (Xe–F ≈ 194 pm). Image: ChemSim, Public Domain, via Wikimedia Commons.
Concept context
Covers the nitrogen family (Group 15), oxygen family (Group 16), halogens (Group 17), and noble gases (Group 18). One of the highest-weightage inorganic chapters in NEET and JEE - includes preparation and properties of HNO₃, H₂SO₄, interhalogens, and xenon compounds.