Advertisements
Advertisements
Question
Some time ago formation of polar stratospheric clouds was reported over Antarctica. Why were these formed? What happens when such clouds break up by warmth of sunlight?
Advertisements
Solution
In summer season, nitrogen dioxide and methane react with chlorine monoxide and chlorine atoms forming chlorine sinks, preventing much ozone depletion, whereas in winter, special type of clouds called polar stratospheric clouds are formed over Antarctica. These polar stratospheric clouds provide surface on which chlorine nitrate gets hydrolysed to form hypochlorous acid. It also reacts with hydrogen chloride to give molecular chlorine.
\[\ce{ClO (g) + NO2 -> ClONO (g)}\]
\[\ce{Cl (g) + CH4 (g) -> CH3 (g) + HCl (g)}\]
\[\ce{ClONO2 (g) + H2O (g) -> HOCl (g) + H2O3}\]
\[\ce{CLONO2 (g) + HCL (g) -> Cl2 (g) + HNO3 (g)}\]
When sunlight returns to the Antarctica in spring, the sun’s warmth breaks up the clouds and HOCl, Cl2 are photolysed by sunlight.
\[\ce{HOCl (g) ->[hv] OH (g) + Cl (g)}\]
\[\ce{Cl2 (g) ->[hv] 2Cl (g)}\]
The chlorine radicals thus formed initiate the chain reaction for ozone depletion.
APPEARS IN
RELATED QUESTIONS
Explain tropospheric pollution in 100 words.
Carbon monoxide gas is more dangerous than carbon dioxide gas. Why?
List gases which are responsible for greenhouse effect.
Statues and monuments in India are affected by acid rain. How?
Which of the following gases is not a green house gas?
The gaseous envelope around the earth is known as atmosphere. The lowest layer of this is extended upto 10 km from sea level, this layer is ______.
The acids present in acid rain are:
(i) Peroxyacetylnitrate
(ii) H2CO3
(iii) HNO3
(iv) H2SO4
Acid rain is known to contain some acids. Name these acids and where from they come in rain?
Match the terms given in Column I with the compounds given in Column II.
| Column I | Column II |
| (i) Acid rain | (a) CHCl2 – CHF2 |
| (ii) Photochemical smog | (b) CO |
| (iii) Combination with haemoglobin | (c) CO2 |
| (iv) Depletion of ozone layer | (d) SO2 |
| (e) Unsaturated hydrocarbons |
Match the pollutants given in Column I with their effects given in Column II.
| Column I | Column II |
| (i) Phosphate fertilisers in water | (a) BOD level of water increases |
| (ii) Methane in air | (b) Acid rain |
| (iii) Synthetic detergents in water | (c) Global warming |
| (iv) Nitrogen oxides in air | (d) Eutrophication |
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.
Assertion (A): Carbon dioxide is one of the important greenhouse gases.
Reason (R): It is largely produced by respiratory function of animals and plants.
Green plants use carbon dioxide for photosynthesis and return oxygen to the atmosphere, even then carbon dioxide is considered to be responsible for greenhouse effect. Explain why?
Which of the following is a secondary pollutant?
The gas released during anaerobic degradation of vegetation may lead to ______.
Assertion (A): Ozone is destroyed by CFCs in the upper stratosphere.
Reason (R): Ozone holes increase the amount of UV radiation reaching the earth.
