Q41 of 50 Page 181

Assertion (A): Photochemical smog is oxidising in nature.

Reason (R): Photochemical smog contains and , which are formed during the sequence of reactions.


(i) Both A and R are correct and R is the correct explanation of A.


(ii) Both A and R are correct but R is not the correct explanation ofA.


(iii) Both A and R are not correct.


(iv) A is not correct but R is correct.


(i) Both A and R are correct and R is the correct explanation of A.

Explanation: Photochemical smog is one of the types of pollution which generally results from the reaction of atmospheric chemicals and sunlight. The primary Photochemical smog component is the ozone along with this it also contains , acrolein, PAN (Peroxy Acetyl Nitrate) and volatile organic compounds like formaldehyde.


The formation of photochemical smog involves multiple reversible oxidation/reductions steps of nitrogen oxides, methane and sulphur oxides.








Now, both nitrogen dioxide and ozone acts as oxidising agents and react with unburnt hydrocarbons and produce other components of photochemical smog – PAN, formaldehyde and acrolein.


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39

Assertion (A): Greenhouse effect was observed in houses usedto grow plants and these are made of green glass.

Reason (R): Greenhouse name has been given because glass houses are made of green glass.


(i) Both A and R are correct and R is the correct explanation of A.


(ii) Both A and R are correct but R is not the correct explanation of A.


(iii) Both A and R are not correct.


(iv) A is not correct but R is correct.


 40

Assertion (A): The pH of acid rain is less than 5.6.

Reason (R): Carbon dioxide present in the atmosphere dissolves in rain water and forms carbonic acid.


(i) Both A and R are correct and R is the correct explanation of A.


(ii) Both A and R are correct but R is not the correct explanationof A.


(iii) Both A and R are not correct.


(iv) A is not correct but R is correct.


 42

Assertion (A): Carbon dioxide is one of the important greenhouse gases.

Reason (R): It is largely produced by respiratory function of


animals and plants.


(i) Both A and R are correct and R is the correct explanation of A.


(ii) Both A and R are correct but R is not the correct explanation of A.


(iii) Both A and R are not correct.


(iv) A is not correct but R is correct


 43

Assertion (A): Ozone is destroyed by solar radiation in upper stratosphere.

Reason (R): Thinning of the ozone layer allows excessive UV radiations to reach the surface of earth.


(i) Both A and R are correct and R is the correct explanation of A.


(ii) Both A and R are correct but R is not the correct explanation of A.


(iii) Both A and R are not correct.


(iv) A is not correct but R is correct