Assertion (A) : $NO_{X}$ and volatile organic compounds (VOCs) are primary precursors in photochemical smog formation.
Reason (R) : $NO_{X}$ and VOCs form oxidants by thermal reactions.
Choose the correct answer :
Assertion (A) Analysis: Photochemical Smog Precursors
The assertion states that $NO_{X}$ (Nitrogen oxides) and volatile organic compounds (VOCs) are primary precursors in photochemical smog formation. This statement is scientifically accurate. These compounds are released into the atmosphere from sources like vehicle exhaust and industrial emissions. They undergo complex chemical reactions initiated by sunlight to form smog.
Reason (R) Analysis: Oxidant Formation Mechanism
The reason suggests that $NO_{X}$ and VOCs form oxidants through thermal reactions. While $NO_{X}$ and VOCs are involved in forming oxidants (like ozone, $O_3$) which contribute to smog, the primary mechanism is not thermal reactions. Photochemical smog formation is fundamentally a photochemical process, meaning it requires energy from solar radiation (sunlight) to drive the reactions. Sunlight breaks down precursor molecules, initiating a chain of reactions that produce ozone and other harmful oxidants.
Therefore, the reason is incorrect because it misattributes the primary reaction mechanism to thermal processes instead of photochemical ones.
Conclusion: Correct Option Selection
Based on the analysis of the assertion and reason:
- Assertion (A) is true.
- Reason (R) is false.
The correct option must state that Assertion (A) is true and Reason (R) is false.
Important Questions from Air and Noise Pollution - Teaching
- Sound pressure is equal to:
- Which of the following air pollutants are responsible for photochemical smog ?
(a) Oxides of nitrogen
(b) Ozone
(c) Unburnt hydrocarbons
(d) Sulphur dioxide
Choose the correct code : If [$_env$ < [$_d$ ,where [$_env$ and [$_d$ are environmental & dry adiabatic lapse rates respectively ,which of the following types of plume emitted from a stack of a thermal power plant is observed ?
- The photodissociation of $NO_{2}$ yields which oxygen species ?
- On take - off, an aeroplane generates noise level of 120 dB. If 5 such aeroplanes take - off simultaneously what will be the noise level ?
