This set of Class 11 Chemistry Chapter 14 Multiple Choice Questions & Answers (MCQs) focuses on “Environmental Chemistry – Atmospheric Pollution”.
1. Identify the correct order of the different regions of the atmosphere.
Explanation: The troposphere is the lowest region of the atmosphere in which human beings and other living organisms live. Above the troposphere, between 10 and 50 km above sea level lies the stratosphere. Then comes the mesosphere, followed by the thermosphere and finally the exosphere.
2. Which of the following is not a gaseous air pollutant?
c) Hydrogen sulphide
Explanation: Fumes come under the category of particulate pollutants and not gaseous air pollutants. It consist of solid particles in the form of suspension in the air. Such particulate pollutants can be released from different types of human activities. Fumes can be released from industries and other chemical plants as well. The other examples of particulate pollutants are dust, mist, smoke, smog, etc.
3. The irritant red haze in traffic and congested places is due to the oxides of which of the following?
Explanation: The irritant red haze in traffic and congested paces is due to the oxides of nitrogen. Haze can refer to aerosols of the wet type that causes reduction in visibility. Nitrogen gas is abundantly found in the atmosphere. This nitrogen will combine with oxygen which is also present in the atmosphere and form nitrogen dioxide. Nitrogen gas has a deep red color. Now, nitrogen dioxide will combine with the aerosols and thus, form the red haze that occur in traffic and congested places.
4. CO has high affinity for haemoglobin.
Explanation: Carbon monoxide (CO) is highly poisonous has a high affinity for haemoglobin. It binds with haemoglobin to form carboxyhaemoglobin, which is about 300 times more stable than the oxygen-haemoglobin complex. In blood, when the concentration of carboxyhaemoglobin reaches about 3-4 per cent, the oxygen carrying capacity of blood is greatly reduced. This oxygen deficiency, results in headache, weak eyesight, nervousness, and cardiovascular disorder.
5. Identify the correct method by which carbon dioxide is produced.
a) By the incomplete combustion of coal or petrol
b) During volcanic eruptions
c) Mainly by automobile exhaust
d) By burning sulfur containing fossil fuels.
Explanation: Volcanic eruptions produce carbon dioxide. The gas is released either during eruptions or through underground magma. Carbon dioxide through underground magma is released through vents, porous rocks, etc. that feeds volcanic lakes. Due to the production of significant amounts of carbon dioxide, volcanoes also contribute to global warming.
6. The amount of carbon dioxide should not cross the delicate proportion of which of the following?
Explanation: The amount of carbon dioxide optimum for the environment should be 0.03 per cent. If this per cent is crossed, then the natural greenhouse balance may get disturbed since carbon dioxide is the major contributor to global warming. But, low concentrations are also not desirable. It can lead to kidney diseases. This condition can cause the body’s blood acid level to go up due to the lack of insulin to digest sugars in the body.
7. Which of the following are the main constituents of acid rain?
a) Carbon, nitrogen
b) Sulphur, oxygen
c) Sulphur, nitrogen
d) Nitrogen, hydrogen
Explanation: Acid rain comprises of the oxides of sulphur and nitrogen. Oxides of nitrogen and sulfur which are acidic in nature can be blown by wind along with solid particles in the atmosphere and finally settle down either on the ground as dry deposition or in water, fog, and snow as wet deposition.
8. When the pH of rain water is above 5.6, then it is called acid rain.
Explanation: On the pH scale, 7 is neutral; below 7 is said to be acidic and above 7 is said to be alkaline. Rain water normally has a pH of 5.6 due to the presence of H+ ions formed by the reaction of rain water with carbon dioxide present in the atmosphere.When the pH of rain water falls below 5.6, then it is called as acid rain.
H2O (l) + CO2 (g)→ H2CO3 (aq)
H2CO3 (aq) → H+ (aq) + HCO3–(aq)
9. Which of the following is the suitable climate for photochemical smog to occur?
a) Cool, humid
b) Dry, warm
c) Sunny, humid
d) Cool, dry
Explanation: Photochemical smog occurs in warm, dry, and sunny climate. The main components of the photochemical smog results from the action of sunlight on unsaturated hydrocarbons and nitrogen oxides produced by automobiles and factories.
10. What is the full form of PAN?
a) Peroxyacetyl nitrate
b) Peroxyacetyl nitrite
c) Peroxyacetylene nitride
d) Peroxyacetyl nitride
Explanation: The full form of PAN is peroxyacetyl nitrate. It is a secondary pollutant present in photochemical smog and is unstable. They dissolve more easily in water than in ozone. It has a chemical formula of C2H3NO5 and a boiling point of 105°C. PAN is formed by oxidation of non-methane volatile organic compounds.
11. Which is the gas that causes eye irritation as a result of photochemical smog?
Explanation: Acrolein is a colorless, clear liquid with a pungent, suffocating odor. It is a toxic gas, to which if exposed, can cause severe irritations in the eye, skin, and also causes respiratory tract irritations. Acrolein is highly flammable and produces toxic concentrations at room temperature.
12. What is the major reason of ozone depletion?
a) Release of CO
b) Release of CO2
c) Release of CFC
d) Release of CH4
Explanation: Chlorofluorocarbons (CFCs), also known as freons, are the major reason for depletion of the protective ozone layer which protects us from the harmful UV radiations, which can be hazardous to human beings and other living organisms. Exposure to UV radiations can cause skin cancer in humans. CFCs, when they reach the stratosphere, will be broken down into free radicals by the UV radiations to liberate chlorine free radical. This chlorine free radical will combine with the stratospheric ozone to form chlorine monoxide and molecular oxygen. In this way, the ozone gets used up and there will be lack of ozone available for protection against UV radiations. Thus, ozone gets depleted.
13. Where does the ozone hole occur?
a) North pole
b) South pole
c) The arctic
Explanation: In the 1980s, depletion of ozone layer, known as ozone hole, over the South Pole. In the summer season, NO2 and CH4 react with chlorine monoxide and chlorine atoms forming chlorine sinks, preventing much ozone depletion. In winter season, special clouds called polar stratospheric clouds are formed over Antarctica.
14. Identify the viable pollutant from the following.
b) Dry leaves
c) Fly ash
d) Oil smoke
Explanation: Moulds is an example of viable pollutant. These are in the category of minute living organisms dispersed in the atmosphere. These can lead to plant diseases. They can also turn out to be allergic to human beings. Changes in temperature or increase in humidity can cause the development of moulds.
15. Pick out the one that is not one of the effects of ozone depletion.
b) Damages paints and fibers
d) Increase in the moisture content of soil
Explanation: Ozone depletion leads to increase in the evaporation of surface water through the stomata of the leaves and decreases the moisture content of the soil. In addition to this, plant proteins get easily affected by UV radiations and therefore, leads to harmful mutation of cells. Thus, ozone depletion has adverse effects on plant life.
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