Why it is so that if aromatic compounds are burned In the air, produce a very smoky flame?
Correct answer: B. The available amount of oxygen present in the air is not sufficient to completely burn the available compound
- A. An aromatic compound cannot be completely converted into CO2 and other products during burning
- B. The available amount of oxygen present in the air is not sufficient to completely burn the available compound
- C. Aromatic compounds produce compounds on burning that are of black color
- D. None of the above
Explanation
Aromatic compounds produce a smoky flame when burned due to their high carbon content. The combustion process requires more oxygen than is typically available in the air to completely convert all carbon into carbon dioxide. Without sufficient oxygen, incomplete combustion occurs, resulting in unburnt carbon particles that give the flame its smoky appearance.Option B is correct because it captures the need for adequate oxygen to complete the combustion of carbon in aromatic compounds. Option A touches on incomplete conversion but does not explain the oxygen requirement. Option C incorrectly attributes the smoky appearance to specific compounds rather than unburnt carbon. Option D is incorrect because the correct explanation is provided in Option B.
This question appeared on the ETEA MDCAT 2012 paper, which you can sit online with every answer explained.
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About Benzene and Aromatic Compounds
Benzene has a planar ring of delocalised π electrons, giving aromatic stability and equal carbon-carbon bond lengths. The topic covers resonance, electrophilic substitution reactions such as nitration, halogenation, sulphonation and Friedel-Crafts reactions, along with substituent effects and the distinction between substitution in benzene and addition in ordinary alkenes.
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