1 Marks Questions

1.What is troposphere?

Ans:The lowest region atmosphere in which the human beings along with other organisms live is called troposphere. It extends upto the height of km from sea level.

2.Name some gaseous air pollutants.

Ans:Gaseous air pollutants are oxides of sulphur, nitrogen and carbon, hydrogen sulphide, hydrocarbons, ozone and other oxidants.

3.What are the diseases caused by sulphur dioxide?

Ans:Sulphur dioxide causes respiratory diseases eg. asthma, bronchitis, emphysema in human beings, sulphur dioxide causes irritation to the eyes, resulting in tears and redness.

4.List gases which are responsible for green house effect?

Ans:Carbon dioxide, methane, water vapors, nitrous oxide, CFC’s and ozone are responsible for green house effect.

5.What is the effect of CFC’s on ozone layer?

Ans: 02Chlorofluorocarbon (CFC’s) damage the ozone layer and creates holes in ozone layer.

6.What is greenhouse effect?

Ans:Atmosphere traps the Sun’s heat near the Earth’s surface and keeps it warm. This is Greenhouse effect.

7.Which disease is caused due to ozone layer depletion?

Ans:Ultraviolet rays reaching the earth passing through the ozone hole cause skin cancer.

8.What is smog?

Ans: When smoke with fog, it is called smog.

9.The London smog is caused in which season and time of the day?

Ans: The London smog is caused during summer season and in the afternoon part of the day when it is very hot.

10.Name two gases which form acid rain.

Ans: 04SO₂ and NO₂.

11.Which acid is present is the acid rain?

Ans: 05The acids present in the acid rain are

H₂SO₄, HNO₃ and HCl.

12.What is PAN?

Ans: 06PAN is Peroxy acetyl nitrate.

13.When does rain water become acid rain?

Ans: 08When pH of rain water becomes as low as 2 to 3.5. It forms acid rain.

14.What is BOD?

Ans: 01BOD stands for Biochemical Oxygen Demand.

15.Define green chemistry.

Ans: 03The branch of chemistry that emphasizes on the processes and products that reduce or eliminate the use and generation of toxic / hazardous substances is called green chemistry.

16.What are pesticides?

Ans: 04Pesticides are those chemicals which are used to destroy pests, rats, parasites and fungi.

17.What should be the pH of drinking water?

Ans:The pH of drinking water should be between 5.5 and 9.5.

18.What is the desirable concentration of fluoride ion (F^-) in drinking water?

Ans:1ppm or 1 mg dm^-3 is desirable concentration of F^- ions in drinking water.

19.What is an insecticide?

Ans: 10Insecticides are used to control insects and curve disease (for eg. malaria and yellow fever) and protect crops. Eg. DDT.

20.Name two air pollutants which forms photochemical smog.

Ans: 03PAN and O₃

21.What is the effect of excess of SO₄^2- ion in drinking water

Ans: Excess of SO₄^2- in drinking water (> 500 ppm) may cause a laxative effect.

2 Marks Questions

1.What is the role of ozone layer in the stratosphere?

Ans. The presence of ozone in the stratosphere prevents about 99.5% of the sun’s harmful ultraviolet (uv) radiations from reaching the earth’s surface and thereby protecting humans and other animals from its effect.

2.What includes stratospheric pollutants? Give examples.

Ans Depletion of ozone layer in stratospheres leading to reach harmful uv radiation on earth is the result of stratospheric pollution. The presence of chloro fluoro carbon compounds in the atmosphere is responsible for this depletion.

3.Why is carbon monoxide considered to be poisonous?

Ans. Carbon monoxide binds to hemoglobin to form carboxyl – haemoglobin, which is about 300 times more stable than the oxygen – haemoglobin complex. In blood when the concentration of carboxyl hemoglobin is greatly reduced. This oxygen deficiency, results into headache, weak eyesight, nervousness and cardiovascular disorder.

4.What are the ill-effects of hydrocarbons?

Ans. Hydrocarbons are carcinogenic i. e; they cause cancer. They harm plants by causing ageing, breakdown of tissues and shedding of leaves flowers and trigs.

5.Give one main reason of ozone depletion?

Ans. The main reason of ozone depletion is the release of chlorofluoro compounds (CFC’s) in the atmosphere also known as Freon.

6.Which zone is called ozonosphere?

AnsStratosphere zone is called ozonosphere.

7.What is ‘greenhouse effect’? How does it affects the global climate?

AnsThe warming of the earth or global warming due to re-emission of sun’s energy absorbed by the earth followed by its absorption by CO₂ molecules and H₂O vapours present in the atmosphere, near the earth’s surface and then its radiation back to the earth is called greenhouse effect.

Greenhouse affects the climate. If the rate at which solar radiation are arriving the earth continues, then the entire global climate is going to change drastically.

8.How can photochemical smog be controlled?

Ans If we control the primary precursors of photochemical smog such as NO₂ and hydrocarbons, the secondary precursors such as ozone and PAN, the photochemical smog will automatically be reduced. Usually catalytic converters are used in the automobiles which prevent the release of nitrogen oxide and hydrocarbon to the atmosphere. Certain plants eg. Pines, Juniparus, Quercus, Pyrus and Vitis can metabolise nitrogen oxide and their plantation could help in this matter.

9.What is the composition of photochemical smog?

Ans Photochemical smog is formed as a result of photochemical reaction (i. e; in the presence of sunlight) between oxides of nitrogen and hydrocarbons.

10.What does the amount of BOD signify?

Ans The amount of BOD in water is a measure of the amount of organic material in the water, in terms of how much oxygen will be required to break it down biologically. Clean water would have BOD value of less than 5 ppm whereas highly polluted water would have a BOD value of 17 ppm or more.

11.What is pneumoconiosis?

Ans The smaller particulate pollutants are more likely to penetrate into the lungs. These five particles are carcinogens Inhalation of small particles irritates the lung and exposure to such particles for long period of time causes fibrosis of the lung lining. These type of disease is termed as pneumoconiosis.

3 Marks Questions

1. What are the harmful effects of oxides of nitrogen in atmosphere?

Ans (i) High concentration of NO₂ in atmosphere is harmful to plants resulting in leaf spotting, retardation of photosynthetic activity and also suppression the vegetation growth.

(ii) Nitrogen dioxide (NO₂) results in respiratory problems in human beings and leads to bronchitis. It causes acid rain. Produce photochemical smog.

(iii) Oxides of nitrogen have harmful effects on the nylon, rayon and cotton yarns and also cause cracks in rubber.

(iv)They also react with react with ozone (O₃) present in the atmosphere, and, their decrease the density of ozone.

2. What are the reactions involved for ozone layer depletion in the atmosphere?

Ans.

3. Why does rain water normally have a pH of about 5.6? When does it become acid rain,

Ans . Rain water normally has a pH of 5.6 due to the formation of H⁺ ions from the reaction of rain water with CO₂ present in the atmosphere.

H₂O + CO₂ → 2H⁺ + CO₃^2-

When the value of pH drops below 5.6, it becomes acidic. Acid rain is also formed due to the presence of oxides of sulphar and nitrogen in the atmosphere.

2SO₂ + O₂ + 2H₂O → 2H₂SO₄

4NO₂ + O₂ + 2H₂O → 4HNO₃.

4.Discuss the water pollution caused by industrial water?

Ans.The compounds of lead, mercury, Cd, Ni, Co, Zn etc which are the products of chemical reactions, carried in the industrial units, pollute water to a large extent and are responsible for many disease. Mercury leads to minimarts disease, lead poisoning leads to many deformities. In addition, these substances adds to the soil and harmfully affect the plant growth and the whole soil biotic system. Both ground water and water bodies are polluted due to chemical reactions known as leaching.