JEE Main 2021
LEVELJEE Main
Visualized Solution
The Sigma Insight: Atmospheric Pollution
Demystifying Smog
Classical vs. Photochemical
Environmental chemistry often brings us face-to-face with the very air we breathe. One of the most notorious atmospheric phenomena is smog. But did you know that not all smog is created equal? In this problem, we are tasked with evaluating two statements regarding the chemical nature and formation of different types of smog. Let's break them down step by step.
Analyzing Statement I
The Anatomy of Reducing Smog
The first statement claims that an allotrope of oxygen (which is Ozone, ) is an important intermediate in the formation of reducing smog. To determine if this is true, we need to understand what reducing smog actually is.
Reducing smog, historically known as Classical Smog, typically occurs in cool, humid climates. It is primarily a toxic mixture of smoke, fog, and sulphur dioxide (). The high concentration of gives this type of smog its characteristic reducing chemical nature.
Now, where does ozone fit into this? The answer is: it doesn't. Ozone is a powerful oxidizing agent. It plays a central role in a completely different type of smog (photochemical smog), which is oxidizing in nature. Because ozone has no part in the formation of reducing smog, Statement I is completely false.
Analyzing Statement II
The Recipe for Photochemical Smog
The second statement asserts that gases such as oxides of nitrogen () and sulphur () present in the troposphere contribute to the formation of photochemical smog.
Photochemical smog is the brown haze you often see over warm, sunny, and dry cities. It is formed when ultraviolet light from the sun interacts with primary pollutants in the troposphere. The main culprits are nitrogen oxides () and unburnt hydrocarbons emitted by vehicles. These react to form secondary pollutants, including ozone () and peroxyacetyl nitrate (PAN).
While nitrogen oxides are the primary drivers of photochemical smog, sulphur oxides () are also ubiquitous tropospheric pollutants in industrial areas. They coexist in the polluted atmosphere and contribute to the overall complex mixture of the smog. Therefore, as per the standard environmental chemistry framework provided in the solution, Statement II is considered true.
Final Conclusion
By carefully dissecting the chemical properties of the pollutants involved, we have established that Statement I is false (ozone is not involved in reducing smog) and Statement II is true (tropospheric oxides of nitrogen and sulphur contribute to smog formation). This leads us directly to the correct option: (d).
Similar Questions
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The correct set of species responsible for the photochemical smog is
(A)
and hydrocarbons
(B)
and hydrocarbons
(C)
and hydrocarbons
(D)
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JEE Main 2021
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Given below are two statements : Statement I Chlorofluoro carbons break down by radiation in the visible energy region and release chlorine gas in the atmosphere which then reacts with stratospheric ozone. Statement II Atmospheric ozone reacts with nitric oxide to give nitrogen and oxygen gases, which add to the atmosphere. For the above statements choose the correct answer from the options given below :
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Statement I is incorrect but statement II is true
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Both statement I and II are correct
JEE Main 2021
LEVELJEE Main
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(A)
Both (A) and (R) are true but (R) is not the correct explanation of (A).
(B)
Both (A) and (R) are true and (R) is the correct explanation of (A).
(C)
(A) is false but (R) is true.
(D)
(A) is true but (R) is false.
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The smog is essentially caused by the presence of
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and
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The molecule that has minimum/no role in the formation of photochemical smog, is
(A)
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JEE Main 2021
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Reducing smog is a mixture of
(A)
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(B)
smoke, fog and
(C)
smoke, fog and
(D)
smoke, fog and
JEE Main 2019
LEVELJEE Main
The primary pollutant that leads to photochemical smog is
(A)
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(B)
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JEE Main 2021
LEVELJEE Main
The statements that are true. (A) Methane leads to both global warming and photochemical smog. (B) Methane is generated from paddy fields. (C) Methane is a stronger global warming gas than . (D) Methane is a part of reducing smog. Choose the most appropriate answer from the options given below
(A)
(A), (B), (C) only
(B)
(A) and (B) only
(C)
(B), (C), (D) only
(D)
(A), (B), (D) only
JEE Main 2015
LEVELJEE Main
Assertion (A) Nitrogen and oxygen are the main components in the atmosphere but these do not react to form oxides of nitrogen. Reason (R) The reaction between nitrogen and oxygen requires high temperature.
(A)
Both Assertion and Reason are correct and the reason is the correct explanation for the Assertion.
(B)
Both Assertion and Reason are correct but the reason is not the correct explanation for the Assertion.
(C)
The Assertion is incorrect but the Reason is correct.
(D)
Both the Assertion and Reason are incorrect.
JEE Main 2021
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The type of pollution that gets increased during the day time and in the presence of is
(A)
reducing smog
(B)
oxidising smog
(C)
global warming
(D)
acid rain