Environmental Chemistry(12th Grade > Chemistry ) Questions and answers for exam Preparation

12th Grade > Chemistry

ENVIRONMENTAL CHEMISTRY MCQs

Total Questions : 40 | Page 1 of 4 pages

Question 1. Assertion (A): Use of Chlorofluorocarbons (CFC’s) is hazardous to environment. Reason (R): CFC’s are very reactive, flammable and toxic gases.

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

Discuss Question

Answer: Option C. -> A is correct but R are not correct.
:
C
CFC’s are responsible for depletion of ozone layer. Hence it is hazardous to environment. But they are non-reactive, non-flammable and non-toxic gases. That’s why they are used in refrigerators.

Question 2. Minamata disease is due to pollution of

organic waste into drinking water
oil spill in water
industrial waste mercury into fishing water
arsenic into the atmosphere

Discuss Question

Answer: Option C. -> industrial waste mercury into fishing water
:
C
Due to Hg poisoning in fishing water,minamataiscaused.

Question 3. Loam soil contains equal amounts of

sand
silt
clay, humus, air and water
all of the above.

Discuss Question

Answer: Option D. -> all of the above.
:
D
Loam soil contains almost equal amounts of sand, silt, clay humus, air and water.

Question 4. Which of the following statement is not true? Reforestation will-

transpire more water vapour
cause more rain fall
increase pollution by particulate matter
raise the underground water level.

Discuss Question

Answer: Option C. -> increase pollution by particulate matter
:
C
Reforestation will decrease the pollution by particulate matter because it helps in deposition of suspended particulates on the leaves which are subsequently washed down by rain waters.

Question 5. Water is often treated with chlorine to

increase oxygen content
kill germs
remove suspended particles
remove hardness

Discuss Question

Answer: Option B. -> kill germs
:
B
Water is treated with chlorine to kill germs.

Question 6. Modes of controlling pollution in large cities include-

less use of insecticides
proper disposal of organic wastes, sewage and industrial effluents.
shifting of factories out of the residential area
all the above.

Discuss Question

Answer: Option D. -> all the above.
:
D
All three can prevent pollution in large cities.

Question 7. Which of the following statement is true about the ozone layer?

It is harmful because ozone is dangerous to living organism
It is beneficial because oxidation reaction can proceed faster in the presence of ozone.
It is beneficial because ozone cuts off the UV radiation of the sun.
It is harmful because ozone cuts out the important radiations of the sun which are vital for photosynthesis.

Discuss Question

Answer: Option C. -> It is beneficial because ozone cuts off the UV radiation of the sun.
:
C
Ozone layer in upper atmosphere absorbs UV radiations and is beneficial to human life.

Question 8.

C F C l_{3}

is responsible for the decomposition of ozone layer. Which of the following reacts with ozone to form oxygen?

Cl2
Cl−
F−
Cl∗

Discuss Question

Answer: Option D. -> Cl∗
:
D
The free radical produced causes destruction of ozone.

C F C l_{3} (g) \to C F C l_{2}^{*} + C l^{*}

C l^{*} (g) + O_{3} (g) \to C l O^{*} + O_{2} (g)

Question 9. Which one is not correct? Greenhouse effect:

Is mainly due to high concentration of CO2 in atmosphere
Is influenced by gases such as CH4, O3 and chlorofluorocarbons
Would result in the warming up of the earth
Would result in lowering the level of oceans due to high evaporation

Discuss Question

Answer: Option D. -> Would result in lowering the level of oceans due to high evaporation
:
D
Greenhouse effect would cause melting of polar ice caps and glaciers that will result in increasing the ocean levels, thereby causing submergence of low lying areas.

Question 10. If BOD of river is high, it means that the river is:

Not polluted
Very much polluted with inorganic chemicals
Very much polluted with organic chemicals which are decomposed by micro-organisms
Polluted with pesticides

Discuss Question

Answer: Option C. -> Very much polluted with organic chemicals which are decomposed by micro-organisms
:
C
BOD is the amount of oxygen required by bacteria to break down the organic matter present in certain volume of water. High BOD means high demand for oxygen, which means high levels of organic pollutants.