Prob 1. Why does rain water have a pH of about 5 – 6?

Sol. Normally rain has a pH of about 5 – 6 due to dissolution CO2 of  of the atmosphere into it.

Prob 2. When does a rain is considered to be acid rain?

Sol.  When the pH of rain falls below 5 – 6, it becomes acid rain.

Prob 3. Explain giving reasons. ‘The presence of CO reduces the amount of haemoglobin available in the blood for carrying oxygen to the body cells’.

Sol. CO combines with haemoglobin of the red blood corpuscles about 300 times more easily than oxygen to form carboxy haemoglobin reversibly as follows:

Thus it is not able to combine with oxygen to form oxyhaemoglobin and transport of oxygen to different body cell cannot take place.

Prob 4. Why is acid rain considered as a threat to ‘Taj Mahal’?

Sol.  Taj Mahal is made of marble. The acid rain contains which attacks the marble  thereby pitting it, decolourising it and making it lustreless.

Prob 5. Fish do not grow as well in warm water as in cold water, why?

Sol.  The amount of dissolved oxygen in warm water is less than in cold water.

Prob 6. Oxygen plays a key role in the troposphere while ozone in the stratosphere. Explain.

Sol. All biological activities take place in the troposphere for which oxygen is required. Ozone in the stratosphere absorbs the harsh UV radiation coming from the sun which otherwise cause skin cancer, affect the cornea of the eye.

Prob 7. What is temperature range of the atmosphere?


Prob 8. Which gas leaked to bring havoc in Bhopal tragedy?

Sol. Methyl isocynate (MIC)

Prob 9. What is % of in the pure dry air?

Sol. About 0.032%

 Prob 10. What is anoxia or asphyxiation?

Sol. Acute oxygen starvation in the body (due to CO poisoning) is called anoxia or asphyxiation.

Prob 11. How are NO and formed in the atmosphere.

Sol. NO is formed due to reaction between during lightening or combustion of Fossil fuels. It is further oxidised to

Prob 12. What is chlorosis?

Sol. Slowing down the formation of chlorophyll in plants due to presence of as pollutant is called chlorosis.

Prob 14. What is the size range of particulates?

Sol. 5 nm to 50,000 nm.

Prob 15. What type of aromatic compounds are present as particulates in the air?

Sol. Polycyclic aromatic hydrocarbon (PAH).

Prob 16. Why is COD preferred over BOD?

Sol. COD can be found in few minutes whereas BOD requires atleast 5 days.

Prob 17.  Name three gases which are major air pollutants.

Sol. CO,

Prob 18. Name three natural sources of air pollution.

Sol. Volcanic eruptions, forest fires and pollen grains of flowers.

Prob 19. What is the compound formed when CO combines with blood.

Sol. Carboxyhaemoglobin (HbCO).

Prob 20. Why ‘photo chemical smog’ is so called?

Sol. It is because it is formed as a result of photo chemical reaction (i.e. in presence of sunlight) between oxides of nitrogen and hydrocarbons.

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