Identify the incorrect statement about air pollutants and sources Evaluate the following statements and choose the one that is wrong.
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ABenzopyrene which causes cancer is present in traces in tobacco, charcoal & petrol driven automobile exhaust.
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BNO2 is capable of penetrating the troposphere and can absorb both ultraviolet & visible light.
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CHydrocarbon pollutants are produced by sweet gum, oak & natural rubber trees.
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DH2S is not at all produced during combustion of sulphur bearing fuels as all the sulphur is oxidised to SO2.
Answer
Correct Answer: H2S is not at all produced during combustion of sulphur bearing fuels as all the sulphur is oxidised to SO2.
Explanation
Introduction / Context:This question blends toxicology, atmospheric chemistry, and combustion science. Correctly spotting the incorrect statement requires recognising typical emission profiles and natural sources of organic vapours.
Given Data / Assumptions:
- Normal combustion systems can operate in regions that are oxidising or locally reducing.
- Biogenic volatile organic compounds (VOCs) are well-documented.
- Nitrogen dioxide (NO2) has distinct optical absorption features.
Concept / Approach:(a) Benzo[a]pyrene (a polycyclic aromatic hydrocarbon) is indeed found in tobacco smoke, char/soot, and exhaust—true. (b) NO2 absorbs in the visible (brown color) and UV; it resides in the troposphere—true. (c) Certain trees emit isoprene/terpenes (hydrocarbons), supporting this statement—true. (d) Claiming H2S is never produced is false: reducing zones, incomplete combustion, or fuel-bound sulfur chemistry can yield H2S alongside SO2.
Step-by-Step Solution:
Assess (a): Known carcinogenic PAH in smoke and exhaust → correct.Assess (b): NO2 has strong visible/UV absorption; tropospheric presence is routine → correct.Assess (c): Biogenic emissions from certain trees (isoprene/monoterpenes) → hydrocarbon pollutants → correct.Assess (d): Absolute statement “not at all” contradicts reducing flame chemistry → incorrect.Verification / Alternative check:Combustion literature notes H2S and COS formation under fuel-rich conditions; flue gas desulfurisation systems also measure reduced sulfur species.
Why Other Options Are Wrong:
(a), (b), (c) align with established observations and are not wrong.Common Pitfalls:Treating combustion as perfectly oxidising everywhere; in real furnaces, mixing and local equivalence ratios vary spatially.
Final Answer:H2S is not at all produced during combustion of sulphur bearing fuels as all the sulphur is oxidised to SO2.