Environmental Issues Test

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Environmental Issues Test - 24

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Weekly Quiz Competition

Question 1
1 / -0

Why is the concentration of ozone less over the north and south poles?

A
CFC's accumulate only in area where the air is cold.

B
CFC use is highest in these areas.

C
CFC's stick to frozen water vapour and are able to act as catalysts.

D
UV rays are stronger in the atmosphere.
Solution
- The geographical location having low temperatures leads to the destruction of ozone present in the stratospheric locations.
- At these temperatures, clouds form in the lower stratosphere from the water vapour.
- CFCs allow the chemical reactions inside them to transform compounds derived from halocarbons into active compounds.
- These processes lead to the rapid destruction of ozone when sunlight returns over the pole. So, the concentration of ozone is less over the north pole and south pole.
Thus, the correct answer is option C.
Question 2
1 / -0

The purpose of biological treatment of waste-water is to

A
Reduce BOD

B
Increase BOD

C
Reduce sedimentation

D
Increase sedimentation

Solution

Decomposition of organic matter by microbes require oxygen. The degree of impurity of water due to organic matter is measured in terms of Biological Oxygen Demand (BOD). BOD is the oxygen required by microorganisms to metabolise organic wastes in the water. Biological treatment of wastewater will reduce the organic impurities or an organic load of polluted water, thus curtail the level of BOD.
So, the correct answer is option A.
Question 3
1 / -0

Protective layer of ozone in the atmosphere exists in which layer?

A
Troposphere

B
Lonosphere

C
Stratosphere

D
Atmosphere

Solution

The ozone layer exists in the lower regions of the stratosphere. Its altitude and thickness may vary depending on the geographical area but it extends over the entire globe. The ozone has a protective role in the upper atmosphere where it prevents the intense UV rays from reaching the earth's surface.
Question 4
1 / -0

Good ozone is found in

A
Atmosphere

B
Biosphere

C
Stratosphere

D
Ozonosphere

Solution

The correct answer is Stratosphere. Option C
Ozone occurs in the Earth's upper atmosphere—10 to 30 miles above the Earth's surface and protects from the sun's harmful ultraviolet (UV) rays Stratospheric ozone is formed naturally by chemical reactions involving solar ultraviolet radiation (sunlight) and oxygen molecules.
Question 5
1 / -0

Biochemical Oxygen Demand (BOD) in a river water

A
Remains unchanged when algal bloom occurs

B
Has no relationship with concentration of oxygen in the water

C
Gives a measure of salmonella in the water

D
Increases when sewage gets mixed with river water
Solution
- Sewage is wastewater having food residue, animal and human excreta, detergent, discharges from industrial and commercial establishments.
- The degree of impurity of water due to organic matter is measured in terms of
- BOD or biochemical oxygen demand. BOD is the oxygen in milligrams required for 5 days in one litre of water at 20 degrees centigrade for the microorganisms to metabolize organic wastes.
- If the water, is polluted with sewage and other organic wastes, the BOD will increase.
- So, the correct answer is option D.
Question 6
1 / -0

Fishes die by sewage because

A
Of its bad smell.

B
It replaces food material of fishes.

C
It increases oxygen competition among fishes.

D
$$CO_2$$ is mixed in large amount in water.

Solution

Sewage discharge in water bodies leads to organic loading or occurrence of excess organic matter inside water body. Its putrefaction decreases dissolved oxygen leading to competition for oxygen among fishes. Also blue green algae bloom and increase in number and release toxins. Both toxicity and decreased oxygen level kill aquatic animals, like fishes.
Question 7
1 / -0

Phosphorus-32 emits

A
$$\alpha$$ particles

B
$$\beta$$ particles

C
$$\gamma$$ particles

D
X-rays
Solution
- The beta particle is a high-energy and high-speed electron that is emitted from the radioactive element.
- Phosphorus-32 is a radioactive isotope of phosphorus. The electron is emitted from it in the form of a beta particle. Phosphorous-32 is used in medicine and molecular biology.
Thus, the correct answer is option B.
Question 8
1 / -0

When huge amount of sewage is dumped into a river, the BOD will

A
Increase

B
Remain unchanged

C
Slightly decrease

D
Decrease

Solution

Decomposition of organic matter by microbes requires oxygen. Degree of impurities of water due to organic matter is measured in terms of 'Biological Oxygen Demand' (BOD). BOD is the oxygen required by microorganisms to metabolise organic wastes. When sewage is dumped into river the BOD increases. Low pollution levels are indicated by BOD below 1500 mg per litre, medium pollution levels are indicated by BOD between 1500 and 4000 mg per litre and high organic pollution is indicated by BOD level above 4000 mg per litre.
Question 9
1 / -0

Which one of the following chemicals is responsible for the reduction of ozone content of atmosphere?

A
Hydrochloric acid

B
Photochemical smog

C
Chlorofluorocarbon (CFC)

D
Sulphur dioxide

Solution

Chlorofluorocarbons or Chlorofluoromethane are also known as freon or aerosols. They are chemicals used as refrigerants, propellants and solid plastic foams. These chemicals are also released as aerosols by jets flying at high altitudes. Along with nitrogen oxides, chlorofluorocarbons react with ozone of ozonosphere and depletes the same. Chlorofluorocarbons release reactive chloride which directly reacts with ozone molecules setting a chain reaction.
Question 10
1 / -0

What are the chief pollutants of the atmosphere, which are most likely to deplete the ozone layer?

A
Sulphur dioxide

B
Nitrogen oxide and Fluorocarbons

C
Carbon dioxide

D
Carbon monoxide

Solution

Chlorofluorocarbons or Chlorofluoromethane are also known as freon or aerosols. They are chemicals used as refrigerants, propellants and solid plastic foams. These chemicals are also released as aerosols by jets flying at high altitudes. Along with nitrogen oxides, chlorofluorocarbons react with ozone of ozonosphere and depletes the same. Chlorofluorocarbons release reactive chloride which directly reacts with ozone molecules setting a chain reaction.
So, the correct answer is option B.

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Re-Attempt Weekly Quiz Competition

Environmental Issues Test - 24

Result

Environmental Issues Test - 24

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SHARING IS CARING

Question 1

CFC's accumulate only in area where the air is cold.

CFC use is highest in these areas.

CFC's stick to frozen water vapour and are able to act as catalysts.

UV rays are stronger in the atmosphere.

Solution

Question 2

Reduce BOD

Increase BOD

Reduce sedimentation

Increase sedimentation

Solution

Question 3

Troposphere

Lonosphere

Stratosphere

Atmosphere

Solution

Question 4

Atmosphere

Biosphere

Stratosphere

Ozonosphere

Solution

Question 5

Remains unchanged when algal bloom occurs

Has no relationship with concentration of oxygen in the water

Gives a measure of salmonella in the water

Increases when sewage gets mixed with river water

Solution

Question 6

Of its bad smell.

It replaces food material of fishes.

It increases oxygen competition among fishes.

$$CO_2$$ is mixed in large amount in water.

Solution

Question 7

$$\alpha$$ particles

$$\beta$$ particles

$$\gamma$$ particles

X-rays

Solution

Question 8

Increase

Remain unchanged

Slightly decrease

Decrease

Solution

Question 9

Hydrochloric acid

Photochemical smog

Chlorofluorocarbon (CFC)

Sulphur dioxide

Solution

Question 10

Sulphur dioxide

Nitrogen oxide and Fluorocarbons

Carbon dioxide

Carbon monoxide

Solution

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