Q1. Which of the following greenhouse gases is primarily responsible for global warming?
a) Carbon monoxide
b) Methane
c) Nitrous oxide
d) Sulfur dioxide
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Correct Answer: b) Methane
Explanation: Methane (CH4) is a potent greenhouse gas, more effective at trapping heat than carbon dioxide (CO2) over a 20-year period. It is mainly emitted from agricultural activities, landfills, and natural gas production. Its high global warming potential makes it a significant contributor to climate change.
Q2. Acid rain is primarily caused by the emissions of:
a) Carbon dioxide
b) Oxygen
c) Sulfur dioxide and nitrogen oxides
d) Methane
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Correct Answer: c) Sulfur dioxide and nitrogen oxides
Explanation: Acid rain forms when sulfur dioxide (SO2) and nitrogen oxides (NOx), primarily emitted from burning fossil fuels, react with water vapor in the atmosphere to form sulfuric acid and nitric acid. These acids can cause environmental damage to forests, aquatic ecosystems, and infrastructure.
Q3. Which of the following pollutants is associated with the depletion of the ozone layer?
a) Carbon dioxide
b) Chlorofluorocarbons (CFCs)
c) Nitrogen dioxide
d) Particulate matter
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Correct Answer: b) Chlorofluorocarbons (CFCs)
Explanation: Chlorofluorocarbons (CFCs) are synthetic compounds used in refrigeration, air conditioning, and aerosol propellants. They release chlorine atoms in the stratosphere, which catalytically destroy ozone molecules, leading to the depletion of the ozone layer and increased ultraviolet radiation reaching the Earth’s surface.
Q4. Which process is responsible for converting nitrogen gas (N2) into forms usable by plants?
a) Denitrification
b) Nitrogen fixation
c) Nitrification
d) Ammonification
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Correct Answer: b) Nitrogen fixation
Explanation: Nitrogen fixation is the process by which certain microorganisms convert atmospheric nitrogen gas (N2) into ammonia (NH3) or other nitrogen compounds that can be utilized by plants for growth and development. This process is essential for maintaining soil fertility and agricultural productivity.
Q5. The main component responsible for the formation of photochemical smog is:
a) Carbon dioxide
b) Nitrogen dioxide
c) Sulfur dioxide
d) Methane
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Correct Answer: b) Nitrogen dioxide
Explanation: Photochemical smog forms when nitrogen oxides (NOx) and volatile organic compounds (VOCs) react with sunlight to produce a complex mixture of pollutants, including ozone and other harmful compounds. Nitrogen dioxide (NO2) is a key component of photochemical smog and contributes to its formation.
Q6. Which of the following pollutants is a major cause of eutrophication in water bodies?
a) Phosphorus
b) Carbon monoxide
c) Lead
d) Mercury
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Correct Answer: a) Phosphorus
Explanation: Phosphorus is a nutrient that, when present in excess in water bodies due to runoff from agricultural activities, urban runoff, or wastewater discharge, can lead to eutrophication. Eutrophication causes excessive growth of algae and aquatic plants, leading to oxygen depletion and harmful algal blooms.
Q7. The process of converting organic matter into simpler compounds by microorganisms under anaerobic conditions is called:
a) Photosynthesis
b) Decomposition
c) Fermentation
d) Combustion
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Correct Answer: b) Decomposition
Explanation: Decomposition is the breakdown of organic matter into simpler compounds by microorganisms such as bacteria and fungi. This process occurs in the absence of oxygen (anaerobic conditions) and plays a crucial role in nutrient cycling and soil formation.
Q8. The term “bioaccumulation” refers to:
a) The gradual breakdown of organic matter by microorganisms
b) The process of converting sunlight into chemical energy by plants
c) The accumulation of toxic substances in the tissues of organisms
d) The conversion of nitrogen gas into ammonia by nitrogen-fixing bacteria
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Correct Answer: c) The accumulation of toxic substances in the tissues of organisms
Explanation: Bioaccumulation occurs when organisms absorb toxic substances, such as heavy metals or persistent organic pollutants, from their environment at a rate faster than they can metabolize or excrete them. This can lead to increased concentrations of these substances in the tissues of organisms higher up the food chain.
Q9. Which of the following is not a greenhouse gas?
a) Carbon dioxide
b) Water vapor
c) Oxygen
d) Methane
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Correct Answer: c) Oxygen
Explanation: Oxygen (O2) is not considered a greenhouse gas because it does not absorb and emit infrared radiation in the Earth’s atmosphere, unlike greenhouse gases such as carbon dioxide, methane, and water vapour.
Q10. The pH of pure water is:
a) 5.5
b) 7
c) 9
d) 11
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Correct Answer: b) 7
Explanation: The pH of pure water is 7, which is considered neutral. At this pH, the concentrations of hydrogen ions (H+) and hydroxide ions (OH-) are equal. pH values below 7 indicate acidic solutions, while pH values above 7 indicate alkaline or basic solutions.