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201. Green Chemistry is fundamentally defined as the design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances. Who coined this term and pioneered the concept?
ⓐ. Mario Molina
ⓑ. Rachel Carson
ⓒ. Paul Anastas and John Warner
ⓓ. Sherwood Rowland
Correct Answer: Paul Anastas and John Warner
Explanation: Paul Anastas and John Warner are widely credited with defining the principles of Green Chemistry in the 1990s, shifting the focus from cleaning up pollution to fundamentally preventing its creation.
202. Which of the following best encapsulates the core philosophy of Green Chemistry?
ⓐ. Cleaning up chemical waste efficiently after it is produced.
ⓑ. Using only natural, non-synthetic raw materials.
ⓒ. Pollution prevention at the molecular level.
ⓓ. Developing technologies to capture carbon emissions.
Correct Answer: Pollution prevention at the molecular level.
Explanation: The core idea is to design chemical reactions and syntheses to be inherently safer and more efficient, thereby preventing the creation of hazardous waste or byproducts from the start (i.e., at the molecular level), rather than treating pollution after the fact.
203. Green Chemistry is often summarized by its reliance on 12 Principles. These principles aim to make chemical synthesis processes:
ⓐ. Faster, cheaper, and more complex.
ⓑ. Safer, more resource-efficient, and less polluting.
ⓒ. Exclusive to renewable energy sources.
ⓓ. Only applicable to pharmaceutical manufacturing.
Correct Answer: Safer, more resource-efficient, and less polluting.
Explanation: The 12 Principles provide a framework to guide chemists toward developing processes that use minimal energy, minimize waste (atom economy), and avoid toxic or explosive reagents, thereby achieving the goals of safety, efficiency, and environmental protection.
204. Which concept emphasizes that it is better to prevent waste than to treat or clean up waste after it has been formed?
ⓐ. The Prevention Principle (Principle 1 of Green Chemistry)
ⓑ. The Polluter Pays Principle
ⓒ. The Precautionary Principle
ⓓ. The At-the-Source Principle
Correct Answer: The Prevention Principle (Principle 1 of Green Chemistry)
Explanation: The first and most foundational principle of Green Chemistry is Prevention. It states that pollution prevention is fundamentally more desirable than post-synthesis waste management, clean-up, or remediation.
205. Green Chemistry primarily focuses on minimizing hazards related to which three areas of chemical practice?
ⓐ. Energy use, transportation costs, and labor
ⓑ. Financial costs, time delays, and regulatory compliance
ⓒ. ${CO}_2$ emissions, water usage, and land degradation
ⓓ. Chemical reagents, solvents, and products
Correct Answer: Chemical reagents, solvents, and products
Explanation: Green Chemistry principles directly address the toxicity and hazard profile of the materials used (reagents), the medium of the reaction (solvents), and the final substance (products), aiming for minimal intrinsic hazard in all three components.
206. The key difference between Green Chemistry and Environmental Chemistry is that:
ⓐ. Environmental Chemistry focuses on ozone depletion, while Green Chemistry focuses on greenhouse gases.
ⓑ. Green Chemistry designs safer processes; Environmental Chemistry studies the fate and effects of pollutants.
ⓒ. Environmental Chemistry is only applicable to water pollution control.
ⓓ. Green Chemistry is purely theoretical, while Environmental Chemistry is practical.
Correct Answer: Green Chemistry designs safer processes; Environmental Chemistry studies the fate and effects of pollutants.
Explanation: Green Chemistry is a proactive engineering and design discipline aimed at preventing pollution (source reduction). Environmental Chemistry is an analytical and descriptive science that studies the movement, concentration, and impact of contaminants already present in the air, water, and soil.
207. According to Green Chemistry, maximizing atom economy means that in a chemical reaction:
ⓐ. The maximum proportion of the starting materials should be incorporated into the final product.
ⓑ. The reaction must be exothermic.
ⓒ. The reaction must occur at room temperature.
ⓓ. Only renewable starting materials must be used.
Correct Answer: The maximum proportion of the starting materials should be incorporated into the final product.
Explanation: Atom Economy (Principle 2) is a metric that measures the efficiency of a reaction by calculating the ratio of the molecular weight of the desired product to the molecular weight of all reactants used. The goal is to minimize the mass of unwanted byproducts (waste).
208. The ultimate goal of applying Green Chemistry principles to manufacturing processes is to achieve what outcome?
ⓐ. Zero-cost production
ⓑ. $100\%$ conversion efficiency
ⓒ. Zero discharge of hazardous substances (Zero Waste Concept)
ⓓ. Exclusive use of biological catalysts
Correct Answer: Zero discharge of hazardous substances (Zero Waste Concept)
Explanation: While $100\%$ atom economy (Principle 2) is a goal, the overall, practical ultimate goal of Green Chemistry is to make the process inherently safe and efficient enough to achieve zero discharge of hazardous waste, aligning with a sustainable Zero Waste Concept.
209. The primary reason Green Chemistry emphasizes the use of safer solvents and reaction conditions is to reduce the risk associated with:
ⓐ. Product purity requirements
ⓑ. Toxicity, fire, and explosion
ⓒ. The speed of the chemical reaction
ⓓ. The color and texture of the final product
Correct Answer: Toxicity, fire, and explosion
Explanation: Many traditional organic solvents are volatile, flammable, or outright toxic (e.g., benzene, carbon tetrachloride). Green Chemistry focuses on replacing these with safer alternatives like water or supercritical ${CO}_2$ to mitigate the risks of worker exposure, fires, and explosions.
210. Which statement is an inherent goal of Green Chemistry principles?
ⓐ. To increase the complexity of chemical synthesis steps.
ⓑ. To design products that degrade slowly in the environment.
ⓒ. To design chemical products that, at the end of their function, break down into innocuous degradation products.
ⓓ. To rely solely on non-catalytic chemical reactions.
Correct Answer: To design chemical products that, at the end of their function, break down into innocuous degradation products.
Explanation: This aligns with Principle 10 (Design for Degradation), which states that chemical products should be designed so that they do not persist in the environment but instead break down into substances that pose no environmental or human health hazard.
211. Which principle of Green Chemistry states that chemical synthetic methods should be designed to maximize the incorporation of all materials used in the process into the final product?
ⓐ. Design for Degradation
ⓑ. Less Hazardous Chemical Syntheses
ⓒ. Prevent Waste
ⓓ. Atom Economy
Correct Answer: Atom Economy
Explanation: Atom Economy (Principle 2) is a metric that measures the efficiency of a reaction by calculating the ratio of the mass of atoms in the final product to the total mass of atoms in all starting materials, with the goal of minimizing waste by maximizing incorporation.
212. Principle 6 of Green Chemistry, “Design for Energy Efficiency,” primarily suggests that energy requirements for chemical processes should be minimized and, if possible, reactions should be conducted under which specific condition?
ⓐ. High-pressure conditions
ⓑ. In the presence of a strong reducing agent
ⓒ. Ambient temperature and pressure
ⓓ. With maximum stirring rate
Correct Answer: Ambient temperature and pressure
Explanation: Conducting reactions at ambient (room) temperature and pressure significantly reduces the need for external heating, cooling, or compression, which are energy-intensive processes, thereby minimizing the environmental impact associated with energy production.
213. The principle “Safer Solvents and Auxiliaries” (Principle 5) advocates for replacing hazardous organic solvents with which greener alternative media whenever possible?
ⓐ. Highly flammable organic liquids
ⓑ. Concentrated strong acids
ⓒ. Water, supercritical fluids (e.g., ${scCO}_2$), or solvent-free conditions
ⓓ. High-boiling petroleum distillates
Correct Answer: Water, supercritical fluids (e.g., ${scCO}_2$), or solvent-free conditions
Explanation: Solvents and separation agents (auxiliaries) often constitute the largest mass of waste in a chemical process. Green Chemistry seeks to replace traditional toxic and volatile organic solvents with safer, non-toxic alternatives like water or supercritical carbon dioxide (${scCO}_2$).
214. The principle “Catalysis” (Principle 9) suggests that catalytic reagents are superior to stoichiometric reagents. A catalyst is better because it:
ⓐ. Is used in small amounts and regenerated, minimizing waste.
ⓑ. Must be used in large amounts to drive the reaction forward.
ⓒ. Is consumed in the reaction, ensuring no residual waste.
ⓓ. Changes the final product’s physical state.
Correct Answer: Is used in small amounts and regenerated, minimizing waste.
Explanation: A catalyst increases the reaction rate without being consumed in the overall reaction. By being used in small, recoverable amounts, it drastically reduces the generation of waste materials compared to stoichiometric reagents, which are consumed and often become byproducts.
215. Which principle requires that analytical methodologies should be developed to allow for continuous monitoring and control of a chemical process during synthesis to minimize the formation of hazardous substances?
ⓐ. Design for Pollution Prevention (Principle 1)
ⓑ. Safer Chemistry for Accident Prevention
ⓒ. Real-time Analysis for Pollution Prevention (Principle 11)
ⓓ. Inherently Safer Chemistry
Correct Answer: Real-time Analysis for Pollution Prevention (Principle 11)
Explanation: Real-time Analysis for Pollution Prevention (Principle 11) stresses the need for analytical tools to monitor a reaction in progress. By immediately detecting the formation of a hazardous intermediate or byproduct, the process can be adjusted before significant pollution occurs.
216. The principle “Less Hazardous Chemical Syntheses” (Principle 3) states that wherever practicable, synthetic methods should be designed to use and generate substances that possess little or no:
ⓐ. Boiling point
ⓑ. Flammability
ⓒ. Molecular weight
ⓓ. Toxicity to human health and the environment
Correct Answer: Toxicity to human health and the environment
Explanation: This principle directly addresses the hazard profile of all chemical species in a reaction (reactants, intermediates, and products), striving to minimize the intrinsic toxicity risk to both workers and the environment.
217. Principle 10, “Design for Degradation,” is applied to a chemical product to ensure it does what after its intended function is complete?
ⓐ. Remains stable for long-term storage
ⓑ. Breaks down into innocuous degradation products
ⓒ. Reacts with atmospheric ${CO}_2$
ⓓ. Is easily crystallized
Correct Answer: Breaks down into innocuous degradation products
Explanation: Design for Degradation requires that chemical products (e.g., pharmaceuticals, pesticides) are designed to be stable during their use but then rapidly decompose into non-toxic, innocuous substances upon release into the environment, preventing persistence and accumulation.
218. The principle “Use of Renewable Feedstocks” (Principle 7) encourages the use of raw materials derived from:
ⓐ. Petroleum and natural gas
ⓑ. Metals and minerals from the Earth’s crust
ⓒ. Agricultural products or biomass rather than depletable fossil fuels
ⓓ. Industrial waste slag
Correct Answer: Agricultural products or biomass rather than depletable fossil fuels
Explanation: Renewable feedstocks are those resources that are replenished naturally (e.g., through photosynthesis). This principle aims to decrease the reliance on finite, depletable, and environmentally damaging fossil fuels and mining operations.
219. The principle “Inherently Safer Chemistry for Accident Prevention” (Principle 12) advises choosing substances and forms of substances that minimize the potential for chemical accidents, including the potential for:
ⓐ. Explosions, fires, and chemical releases
ⓑ. High product yields
ⓒ. Extended reaction times
ⓓ. Low material costs
Correct Answer: Explosions, fires, and chemical releases
Explanation: This principle focuses on intrinsic process safety. It suggests that by selecting safer substances (less flammable, less reactive, less explosive), the risk of catastrophic events like explosions, fires, and accidental releases is minimized, making the process inherently safer.
220. Which principle focuses on minimizing the formation of derivatives, such as the use of temporary protecting groups, which adds extra steps to a synthesis and generates more waste?
ⓐ. Design for Energy Efficiency
ⓑ. Avoid Derivatization (Principle 8)
ⓒ. Use of Stoichiometric Reagents
ⓓ. Safer Solvents and Auxiliaries
Correct Answer: Avoid Derivatization (Principle 8)
Explanation: Avoid Derivatization suggests that unnecessary chemical modifications (like using protecting groups which require subsequent deprotection steps) should be avoided because these extra steps consume additional reagents and generate significant amounts of extra waste.
221. The production of biodiesel from vegetable oils or animal fats via transesterification is a key application of Green Chemistry because it:
ⓐ. Requires extremely high temperatures and pressures.
ⓑ. Uses large amounts of toxic petroleum-based solvents.
ⓒ. Utilizes a renewable feedstock and minimizes reliance on fossil fuels.
ⓓ. Generates significant volumes of hazardous glycerol as waste.
Correct Answer: Utilizes a renewable feedstock and minimizes reliance on fossil fuels.
Explanation: Biodiesel relies on renewable feedstocks (Principle 7) like soybean oil or waste cooking oil. This reduces dependence on finite petroleum reserves and closes the carbon cycle, aligning with key Green Chemistry goals.
222. Solvent-free reactions (or solid-state synthesis) directly address which two major principles of Green Chemistry?
ⓐ. Safer Solvents and Auxiliaries, and Design for Energy Efficiency
ⓑ. Design for Degradation and Prevention
ⓒ. Atom Economy and Catalysis
ⓓ. Inherently Safer Chemistry and Use of Renewable Feedstocks
Correct Answer: Safer Solvents and Auxiliaries, and Design for Energy Efficiency
Explanation: Eliminating solvents completely adheres to the “Safer Solvents” principle (Principle 5) by removing the largest single source of waste. It also contributes to “Energy Efficiency” (Principle 6) by eliminating the energy required for solvent heating, cooling, distillation, and recovery.
223. Bioethanol is an alternative fuel produced primarily by the fermentation of sugars derived from crops like corn, sugarcane, or cellulosic biomass. This production method is an application of Green Chemistry that emphasizes the use of:
ⓐ. Hazardous strong acids
ⓑ. Non-renewable materials
ⓒ. High-pressure liquid chromatography
ⓓ. Catalytic reagents (enzymes/microbes)
Correct Answer: Catalytic reagents (enzymes/microbes)
Explanation: Fermentation is a biological process catalyzed by living organisms (yeast or bacteria) or their purified enzymes. The use of biological catalysts (biocatalysis) is a pillar of Green Chemistry as it typically occurs under mild, ambient conditions, replacing harsh, energy-intensive chemical catalysts.
224. Poly-Lactic Acid (${PLA}$) is a common example of a biodegradable plastic. Its biodegradability directly aligns with which Green Chemistry principle?
ⓐ. Real-time Analysis for Pollution Prevention
ⓑ. Design for Degradation
ⓒ. Less Hazardous Chemical Syntheses
ⓓ. Atom Economy
Correct Answer: Design for Degradation
Explanation: ${PLA}$ is designed to break down under certain environmental conditions into harmless substances (lactic acid and ${CO}_2$). This characteristic adheres to Design for Degradation (Principle 10), ensuring that the product does not persist as litter or long-term pollution.
225. Supercritical ${CO}_2$ (${scCO}_2$) is an increasingly used green alternative to organic solvents in processes like dry cleaning and chemical extraction because it:
ⓐ. Is flammable and highly toxic.
ⓑ. Generates large amounts of liquid sludge waste.
ⓒ. Requires vacuum conditions for its use.
ⓓ. Is non-toxic, non-flammable, and easily recycled by simple pressure changes.
Correct Answer: Is non-toxic, non-flammable, and easily recycled by simple pressure changes.
Explanation: ${scCO}_2$ acts as an excellent, tunable solvent when subjected to high pressure and moderate temperature. Because it is non-toxic, non-flammable, and can be separated from the product simply by reducing pressure (where it reverts to a gas), it is considered a very safe and recyclable green solvent substitute (Principle 5).
226. The key challenge that the development of lignocellulosic biofuels (from agricultural waste like stalks and wood chips) attempts to solve, in alignment with Green Chemistry, is:
ⓐ. Competition with food crops for arable land resources.
ⓑ. The need for stronger chemical catalysts.
ⓒ. The elimination of all nitrogen oxide emissions.
ⓓ. The high toxicity of the fuel itself.
Correct Answer: Competition with food crops for arable land resources.
Explanation: First-generation biofuels use food crops (corn, sugarcane). Lignocellulosic biofuels (second-generation) utilize non-food plant matter, like agricultural residues or dedicated energy crops grown on marginal land. This addresses the ethical and resource management issue of food vs. fuel competition, maximizing resource efficiency (Principle 7).
227. In the context of Green Chemistry, the synthesis of many polymers is moving toward polycondensation (step-growth) reactions in the solid state rather than traditional solution polymerization. This shift is primarily to avoid the massive use of:
ⓐ. High-cost monomers
ⓑ. Volatile Organic Solvents (${VOCs}$)
ⓒ. Metal catalysts
ⓓ. Thermal energy input
Correct Answer: Volatile Organic Solvents (${VOCs}$)
Explanation: Traditional polymer synthesis requires large volumes of liquid solvents to dissolve the reactants and control viscosity. Shifting to solid-state or bulk polymerization directly eliminates the use of these ${VOC}$ solvents, adhering to the “Safer Solvents” principle (Principle 5).
228. Which characteristic of biodegradable plastics (${BDPs}$) prevents them from becoming a long-term problem in landfills and the marine environment?
ⓐ. They have high tensile strength.
ⓑ. They are cheaper to manufacture.
ⓒ. They are chemically designed to break down via microbial action or hydrolysis.
ⓓ. They require very high temperatures to melt.
Correct Answer: They are chemically designed to break down via microbial action or hydrolysis.
Explanation: ${BDPs}$ are designed with unstable links in their polymer chain that can be broken by enzymes secreted by microorganisms or by water (hydrolysis). This ensures their non-persistence, fulfilling the Design for Degradation principle (Principle 10).
229. Solvent-free synthesis often leads to much faster reaction rates, better selectivity, and higher yields compared to solution-based reactions. This efficiency gain contributes directly to which Green Chemistry principle?
ⓐ. Use of Renewable Feedstocks
ⓑ. Less Hazardous Chemical Syntheses
ⓒ. Design for Energy Efficiency
ⓓ. Inherently Safer Chemistry
Correct Answer: Design for Energy Efficiency
Explanation: Faster reactions and higher yields mean the process runs for less time and uses less starting material per unit of product, leading to reduced energy consumption over the entire manufacturing cycle. This is a direct benefit of the Design for Energy Efficiency principle (Principle 6).
230. A key application of Green Chemistry is the replacement of highly toxic heavy metal catalysts (e.g., Lead or Mercury) with more environmentally benign alternatives, such as:
ⓐ. Strong oxidizing agents (e.g., permanganate)
ⓑ. Organocatalysts or Biocatalysts (enzymes)
ⓒ. High-pressure ${H}_2$ gas
ⓓ. Extremely corrosive mineral acids
Correct Answer: Organocatalysts or Biocatalysts (enzymes)
Explanation: The use of metal-free organocatalysts (small organic molecules) and biocatalysts (enzymes) eliminates the hazard associated with heavy metal toxicity, disposal, and recovery, aligning with the principles of Catalysis (Principle 9) and Less Hazardous Chemical Syntheses (Principle 3).
231. Acid rain is formed when water vapor in the atmosphere reacts with the oxides of Sulphur and Nitrogen. The two primary gaseous precursors are:
ⓐ. Sulphur Dioxide (${SO}_2$) and Nitrogen Oxides (${NO}_{{x}}$)
ⓑ. Carbon Monoxide (${CO}$) and Methane (${CH}_4$)
ⓒ. Chlorofluorocarbons (${CFCs}$) and Ozone (${O}_3$)
ⓓ. Carbon Dioxide (${CO}_2$) and Water Vapor (${H}_2{O}$)
Correct Answer: Sulphur Dioxide (${SO}_2$) and Nitrogen Oxides (${NO}_{{x}}$)
Explanation: ${SO}_2$ and ${NO}_{{x}}$, released primarily from industrial combustion and vehicular exhaust, react with water and oxygen in the atmosphere to form sulfuric acid (${H}_2{SO}_4$) and nitric acid (${HNO}_3$), which fall as acid rain.
232. The Greenhouse Effect occurs when certain atmospheric gases trap heat by:
ⓐ. Absorbing incoming short-wave solar radiation (${UV}$).
ⓑ. Absorbing outgoing long-wave infrared radiation (heat) emitted by the Earth’s surface.
ⓒ. Chemically reacting with water molecules in the clouds.
ⓓ. Reflecting solar radiation back into space.
Correct Answer: Absorbing outgoing long-wave infrared radiation (heat) emitted by the Earth’s surface.
Explanation: Greenhouse gases (${CO}_2, {CH}_4, {N}_2{O}$) allow visible solar radiation to pass through to the Earth, but they effectively absorb the infrared heat radiated back up by the planet’s surface, trapping it and warming the atmosphere.
233. How does the release of Chlorofluorocarbons (${CFCs}$) cause the depletion of stratospheric ozone (${O}_3$)?
ⓐ. ${CFCs}$ absorb all ${UV}$ radiation, starving the ozone layer.
ⓑ. ${CFCs}$ react with ${CO}_2$ to form a protective shield.
ⓒ. ${CFCs}$ release chlorine atoms, which act as catalysts to break down ozone molecules.
ⓓ. ${CFCs}$ cool the stratosphere, which prevents ozone formation.
Correct Answer: ${CFCs}$ release chlorine atoms, which act as catalysts to break down ozone molecules.
Explanation: ${CFCs}$ are photolyzed by ${UV}$ radiation in the stratosphere, releasing highly reactive chlorine atoms (${Cl}$), which can then catalytically destroy tens of thousands of ${O}_3$ molecules, leading to ozone depletion.
234. The most significant and persistent area of stratospheric ozone depletion, often referred to as the “ozone hole,” occurs annually over which geographical area?
ⓐ. The Arctic
ⓑ. The Equator
ⓒ. North America
ⓓ. Antarctica
Correct Answer: Antarctica
Explanation: The most severe ozone depletion happens over the Antarctic during the Southern Hemisphere spring (September to November). This is due to the extremely cold temperatures and the presence of polar stratospheric clouds (PSCs), which facilitate the ozone-destroying chemical reactions.
235. The single largest contributor to the human-induced increase in atmospheric Carbon Dioxide (${CO}_2$) since the industrial revolution is:
ⓐ. The burning of fossil fuels (coal, oil, and natural gas)
ⓑ. Volcanic eruptions and geothermal activity
ⓒ. Deforestation and land-use change
ⓓ. Increased water vapor condensation
Correct Answer: The burning of fossil fuels (coal, oil, and natural gas)
Explanation: While deforestation (C) is a major contributor, the overwhelming source of anthropogenic ${CO}_2$ is the combustion of fossil fuels for energy, transportation, and industrial processes, which releases stored geological carbon into the atmosphere.
236. A visible effect of acid rain on the human environment is the damage caused to historical monuments, statues, and buildings made of marble or limestone. This process is called:
ⓐ. Neutralization
ⓑ. Biological oxidation
ⓒ. Stone leprosy or weathering
ⓓ. Thermal expansion
Correct Answer: Stone leprosy or weathering
Explanation: The sulfuric and nitric acids in acid rain chemically react with calcium carbonate (${CaCO}_3$) found in marble and limestone, slowly dissolving the material. This process, often termed stone leprosy, leads to the erosion, pitting, and etching of historic structures.
237. The primary environmental concern resulting from the depletion of the protective stratospheric ozone layer is:
ⓐ. A decrease in global average temperatures.
ⓑ. Increased levels of harmful Ultraviolet-B (${UV-B}$) radiation reaching the Earth’s surface.
ⓒ. The enhancement of the natural greenhouse effect.
ⓓ. A massive increase in acid precipitation.
Correct Answer: Increased levels of harmful Ultraviolet-B (${UV-B}$) radiation reaching the Earth’s surface.
Explanation: The stratospheric ozone layer is critical because it absorbs most of the high-energy ${UV-B}$ radiation. Its depletion allows more ${UV-B}$ to penetrate, increasing the risks of skin cancer, cataracts, and immune suppression in humans, and damage to crops and marine life.
238. Global Warming Potential (${GWP}$) is a metric used to compare the warming impact of different greenhouse gases. ${GWP}$ is calculated based on the gas’s ability to absorb infrared radiation and its:
ⓐ. Atmospheric lifetime (how long it remains in the atmosphere)
ⓑ. Solubility in seawater
ⓒ. Total concentration in the stratosphere
ⓓ. Rate of chemical reaction with ${CO}_2$
Correct Answer: Atmospheric lifetime (how long it remains in the atmosphere)
Explanation: The ${GWP}$ is a measure of how much energy the emissions of 1 ton of a gas will absorb over a given period (usually 100 years), relative to 1 ton of ${CO}_2$. It is highly dependent on both the gas’s heat-trapping efficiency and its atmospheric lifetime.
239. Which international treaty, adopted in 1997, first set legally binding emission reduction targets for developed countries to combat climate change?
ⓐ. The Montreal Protocol
ⓑ. The Paris Agreement
ⓒ. The Convention on Biological Diversity
ⓓ. The Kyoto Protocol
Correct Answer: The Kyoto Protocol
Explanation: The Kyoto Protocol was the first major international agreement under the United Nations Framework Convention on Climate Change (${UNFCCC}$) to establish mandatory greenhouse gas emission reduction commitments for industrialized nations.
240. The world’s largest natural sink (storage area) for atmospheric ${CO}_2$ is:
ⓐ. Terrestrial plants and soils
ⓑ. The oceans
ⓒ. Polar ice caps
ⓓ. Deep geological repositories
Correct Answer: The oceans
Explanation: The oceans absorb massive amounts of ${CO}_2$ through physical and biological processes, making them the largest natural reservoir for carbon, though this absorption also leads to the problem of ocean acidification.
241. Methane (${CH}_4$) has a much shorter atmospheric lifetime (about 12 years) compared to Carbon Dioxide (${CO}_2$) (hundreds of years). Despite this, Methane is considered a very potent greenhouse gas because its Global Warming Potential (${GWP}$) over a 100-year period is:
ⓐ. Exactly 1, the same as ${CO}_2$.
ⓑ. Approximately 25 to 30 times higher than ${CO}_2$.
ⓒ. Less than 1, making it a cooling agent.
ⓓ. Over 500 times higher than ${CO}_2$.
Correct Answer: Approximately 25 to 30 times higher than ${CO}_2$.
Explanation: Although short-lived, Methane is vastly more efficient at trapping heat than ${CO}_2$. The ${GWP}_{100}$ value is typically cited as $\sim 28$, meaning one ton of ${CH}_4$ warms the planet as much as 28 tons of ${CO}_2$ over a century.
242. Ocean acidification is a direct consequence of increasing atmospheric ${CO}_2$. The chemical reaction that causes the ocean’s ${pH}$ to drop is the ${CO}_2$ reacting with water (${H}_2{O}$) to form:
ⓐ. Sodium Chloride (${NaCl}$)
ⓑ. Molecular Oxygen (${O}_2$)
ⓒ. Carbonic Acid (${H}_2{CO}_3$)
ⓓ. Methane (${CH}_4$)
Correct Answer: Carbonic Acid (${H}_2{CO}_3$)
Explanation: When the ocean absorbs excess atmospheric ${CO}_2$, the ${CO}_2$ dissolves and reacts with water to form carbonic acid (${H}_2{CO}_3$). This acid releases hydrogen ions (${H}^{+}$), which lowers the water’s ${pH}$ and reduces the availability of carbonate ions needed by shell-forming marine organisms.
243. The localized phenomenon where acidic particles (${SO}_2$ and ${NO}_{{x}}$ derivatives) are trapped and concentrated within low-hanging, damp air is referred to as:
ⓐ. Acid fog or acid mist
ⓑ. Photochemical Smog
ⓒ. Thermal inversion
ⓓ. Stratospheric ozone depletion
Correct Answer: Acid fog or acid mist
Explanation: Acid fog or mist occurs when acidic pollutants dissolve in fog droplets. Since fog is much denser than rain, these droplets can contain up to 40 times more acidity than acid rain, causing severe, localized damage to vegetation and structures.
244. Despite the success of the Montreal Protocol, scientists estimate that the stratospheric ozone layer will not return to pre-1980 levels globally until approximately:
ⓐ. 2030
ⓑ. 2050
ⓒ. 2080
ⓓ. 2060s or later
Correct Answer: 2060s or later
Explanation: Due to the very long atmospheric lifetime of the ${CFCs}$ that have already been released, it takes decades for them to break down and for the ozone layer to naturally recover. Current projections place the global recovery around the 2060s, with the Antarctic hole closing slightly later.
245. Acid rain affects soil quality by causing the leaching (removal) of essential nutrients required for plant growth, most notably:
ⓐ. Nitrogen and Phosphorus
ⓑ. Iron and Copper
ⓒ. Calcium and Magnesium
ⓓ. Chlorine and Fluorine
Correct Answer: Calcium and Magnesium
Explanation: The hydrogen ions (${H}^{+}$) from acid rain displace positively charged essential nutrient ions like calcium (${Ca}^{2+}$) and magnesium (${Mg}^{2+}$) from the soil particles. These vital nutrients are then washed away, or leached, making the soil less fertile.
246. The single largest anthropogenic (human-caused) source of Nitrous Oxide (${N}_2{O}$) emissions, which is both a potent greenhouse gas and an ozone-depleting substance, is:
ⓐ. Agricultural soil management (application of synthetic and organic fertilizers)
ⓑ. High-altitude commercial jet travel
ⓒ. Nuclear power generation
ⓓ. Solid waste incineration
Correct Answer: Agricultural soil management (application of synthetic and organic fertilizers)
Explanation: The vast majority of anthropogenic ${N}_2{O}$ emissions come from the microbial processes of nitrification and denitrification that occur in soils, especially after the application of nitrogen-based synthetic and organic fertilizers used heavily in agriculture.
247. The primary reason why the persistent pesticide ${DDT}$ is biomagnified in the food chain is due to its characteristic of being:
ⓐ. Highly fat-soluble (lipophilic)
ⓑ. Highly water-soluble (hydrophilic)
ⓒ. Highly volatile
ⓓ. Extremely reactive with oxygen
Correct Answer: Highly fat-soluble (lipophilic)
Explanation: ${DDT}$ is lipophilic, meaning it readily dissolves in and accumulates within the fatty tissues of organisms. Since it is non-biodegradable and accumulates at each trophic level, this fat-solubility is the chemical basis for biomagnification.
248. Chemical Oxygen Demand (${COD}$) is a measurement often used alongside Biochemical Oxygen Demand (${BOD}$) in wastewater analysis. The key difference is that ${COD}$ measures:
ⓐ. Only the oxygen consumed by biodegradable organic matter.
ⓑ. Only inorganic pollutants in the water.
ⓒ. The oxygen required to chemically oxidize both biodegradable and non-biodegradable organic matter.
ⓓ. The total dissolved solids content.
Correct Answer: The oxygen required to chemically oxidize both biodegradable and non-biodegradable organic matter.
Explanation: ${BOD}$ measures only the oxygen consumed by microbes to degrade biodegradable matter. ${COD}$ uses a strong chemical oxidant (e.g., potassium dichromate) to measure the total oxygen equivalent of nearly all oxidizable organic matter, including the non-biodegradable fractions.
249. The formation of the protective stratospheric ozone layer (${O}_3$) is primarily initiated by which process?
ⓐ. The reaction of ${NO}$ and ${VOCs}$ from pollution.
ⓑ. Photolysis (the breaking of ${O}_2$ by high-energy ${UV}$ radiation).
ⓒ. The oxidation of water vapor.
ⓓ. The breakdown of ${CFCs}$ by visible light.
Correct Answer: Photolysis (the breaking of ${O}_2$ by high-energy ${UV}$ radiation).
Explanation: Ozone formation begins when high-energy ${UV}$ light breaks an oxygen molecule (${O}_2$) into two free oxygen atoms (${O}$). These highly reactive oxygen atoms then combine with other ${O}_2$ molecules to form ozone (${O}_3$).
250. Which heavy metal impurity, if present in fuel, will permanently poison and render a vehicular catalytic converter useless?
ⓐ. Lead (${Pb}$)
ⓑ. Zinc (${Zn}$)
ⓒ. Iron (${Fe}$)
ⓓ. Nickel (${Ni}$)
Correct Answer: Lead (${Pb}$)
Explanation: Leaded gasoline was phased out globally because lead deposits coated the precious metal catalysts (${Pt}, {Pd}, {Rh}$) within the converter, preventing the catalytic reactions and effectively poisoning the device.
251. Minamata disease is a neurological syndrome caused by severe poisoning from which heavy metal, often accumulating in fish and shellfish?
ⓐ. Cadmium (${Cd}$)
ⓑ. Lead (${Pb}$)
ⓒ. Arsenic (${As}$)
ⓓ. Mercury (${Hg}$)
Correct Answer: Mercury (${Hg}$)
Explanation: Minamata disease was first discovered in Japan, caused by the release of industrial wastewater containing methylmercury (an organomercury compound) which bioaccumulated in seafood and was consumed by the local population.
252. The primary source of Sulphur Oxides (${SO}_{{x}}$) emissions globally is the combustion of:
ⓐ. Gasoline in automobiles
ⓑ. Natural gas for residential heating
ⓒ. Sulphur-containing coal and oil in power plants
ⓓ. Biomass for cooking
Correct Answer: Sulphur-containing coal and oil in power plants
Explanation: Coal and heavy fuel oil contain significant amounts of sulphur. The vast majority of global ${SO}_{{x}}$ emissions, the precursor to acid rain, results from burning these fuels in thermal power stations and industrial boilers.
253. The Exhaust Gas Recirculation (${EGR}$) system in a vehicle controls emissions by lowering the combustion temperature. Lowering the temperature directly suppresses the formation of which pollutant?
ⓐ. Carbon Monoxide (${CO}$)
ⓑ. Nitrogen Oxides (${NO}_{{x}}$)
ⓒ. Particulate Matter (${PM}$)
ⓓ. Unburnt Hydrocarbons (${HC}$)
Correct Answer: Nitrogen Oxides (${NO}_{{x}}$)
Explanation: ${NO}_{{x}}$ is a product of high-temperature combustion (${N}_2 + {O}_2 \rightarrow 2{NO}$ at high heat). The ${EGR}$ system recirculates inert exhaust gas into the engine, which acts as a thermal ballast, lowering the peak combustion temperature and dramatically reducing ${NO}_{{x}}$ formation.
254. Persistent Organic Pollutants (${POPs}$) like ${DDT}$ and ${PCBs}$ are difficult to remove from the environment primarily because they are:
ⓐ. Chemically and biologically resistant to degradation
ⓑ. Highly reactive with atmospheric oxygen
ⓒ. Naturally found in soil minerals
ⓓ. Easily dissolved by acid rain
Correct Answer: Chemically and biologically resistant to degradation
Explanation: The term ‘Persistent’ refers to the stability of their chemical structure, which resists breakdown by hydrolysis, photolysis, or biological metabolism (microbes), allowing them to persist in the environment for decades.
255. In a modern sanitary landfill, the primary purpose of the thick, impermeable layer of clay or high-density plastic sheeting at the base is to:
ⓐ. Increase the decomposition rate of the waste.
ⓑ. Provide structural support for the waste layers.
ⓒ. Prevent the escape of toxic leachate into the groundwater.
ⓓ. Facilitate the collection of methane gas (${CH}_4$).
Correct Answer: Prevent the escape of toxic leachate into the groundwater.
Explanation: The liner system (clay and synthetic membranes) is a containment barrier designed to collect and isolate leachate (toxic liquid produced as water percolates through the waste) from contaminating underlying soil and groundwater (Principle of Containment).
256. The Green Chemistry principle “Use of Renewable Feedstocks” most directly encourages the shift from using materials derived from which source?
ⓐ. Biomass (plants and animals)
ⓑ. Petroleum and mined minerals
ⓒ. Water and air
ⓓ. Recycled plastics
Correct Answer: Petroleum and mined minerals
Explanation: Renewable feedstocks are derived from biomass (e.g., sugar, plant oils) that can be regenerated on a human timescale. Non-renewable feedstocks are finite resources, primarily petroleum (fossil carbon) and mined geological minerals, which Green Chemistry seeks to reduce reliance upon.
257. In the formation of photochemical smog, the highly reactive species that contributes significantly to rapid chemical cycling and the formation of ${O}_3$ and ${PAN}$ is the:
ⓐ. Carbon Monoxide (${CO}$) radical
ⓑ. Sulphur Dioxide (${SO}_2$) radical
ⓒ. Hydrogen Peroxide (${H}_2{O}_2$)
ⓓ. Hydroxyl radical (${OH}^{\\bullet}$) and Peroxy radicals (${RO}_2^{\\bullet}$)
Correct Answer: Hydroxyl radical (${OH}^{\\bullet}$) and Peroxy radicals (${RO}_2^{\\bullet}$)
Explanation: The hydroxyl radical (${OH}^{\\bullet}$) is the ‘detergent’ of the atmosphere. It initiates the oxidation of ${VOCs}$ and hydrocarbons, forming peroxy radicals (${RO}_2^{\\bullet}$). These radicals propagate the chain reaction that converts ${NO}$ to ${NO}_2$ (which forms ozone) and leads to ${PAN}$ formation.
258. The solubility characteristic of many major soil pollutants, such as heavy metals and certain ionic compounds, that makes them non-leaching (i.e., less likely to wash away) is:
ⓐ. High volatility
ⓑ. High solubility in water
ⓒ. Low solubility (they are retained/adsorbed by soil particles)
ⓓ. High rate of microbial degradation
Correct Answer: Low solubility (they are retained/adsorbed by soil particles)
Explanation: Many heavy metals and pollutants become tightly bound (adsorbed) to soil particles like clay and organic matter. Their low solubility prevents them from easily dissolving in rainwater and leaching out into the groundwater, thus contributing to their persistence as soil pollutants.
259. A significant consequence of thermal pollution in water bodies is the severe stress placed on fish and aquatic organisms due to:
ⓐ. A decrease in the concentration of Dissolved Oxygen (${DO}$)
ⓑ. An increase in the water’s ${pH}$ level
ⓒ. A decrease in the rate of microbial decomposition
ⓓ. An increase in the water’s viscosity
Correct Answer: A decrease in the concentration of Dissolved Oxygen (${DO}$)
Explanation: The solubility of gases (like oxygen) in water is inversely proportional to temperature. When the water temperature increases due to thermal pollution, the Dissolved Oxygen (${DO}$) concentration drops, leading to oxygen stress or death (asphyxiation) for fish.
260. Which Green Chemistry principle is summarized by the statement: “It is better to prevent waste than to treat or clean up waste after it has been formed”?
ⓐ. Design for Degradation
ⓑ. Atom Economy
ⓒ. Prevention
ⓓ. Catalysis
Correct Answer: Prevention
Explanation: Prevention (Principle 1) is the foundational principle of Green Chemistry, emphasizing that chemical syntheses should be designed to eliminate waste generation at the source, rather than managing waste downstream.
261. In the context of water quality assessment, water is generally considered “clean” and suitable for aquatic life if the concentration of Dissolved Oxygen (${DO}$) is consistently above:
ⓐ. $1{ ppm}$
ⓑ. $25{ ppm}$
ⓒ. $15{ ppm}$
ⓓ. $6{ ppm}$
Correct Answer: $6{ ppm}$
Explanation: While a ${DO}$ of $8-10{ ppm}$ is ideal, water with a ${DO}$ level consistently below $4-5{ ppm}$ is usually considered highly polluted and detrimental to fish life. A value above $6{ ppm}$ is generally classified as supporting healthy aquatic life.
262. In water quality testing, a Biochemical Oxygen Demand (${BOD}$) value greater than which amount generally indicates a highly polluted water source unsuitable for sustaining fish life?
ⓐ. $1{ ppm}$
ⓑ. $5{ ppm}$
ⓒ. $17{ ppm}$
ⓓ. $30{ ppm}$
Correct Answer: $17{ ppm}$
Explanation: Water with a ${BOD}$ below $5{ ppm}$ is generally considered clean. Moderately polluted water has ${BOD}$ between $5-15{ ppm}$. Highly polluted water, such as municipal sewage, often has a ${BOD}$ value exceeding $15-17{ ppm}$, indicating high levels of decomposable organic matter and severe oxygen depletion risk.
263. The process of converting organic solid waste (like vegetable and food scraps) into a nutrient-rich soil amendment through aerobic decomposition by microorganisms is called:
ⓐ. Incineration
ⓑ. Composting
ⓒ. Pyrolysis
ⓓ. Landfilling
Correct Answer: Composting
Explanation: Composting is a biological process where organic waste breaks down under aerobic (oxygen-rich) conditions to form humus, a valuable fertilizer. This is a primary method of decentralized solid waste management.
264. The highly toxic compound formed in photochemical smog that acts as a strong eye irritant and respiratory toxin, often summarized by the formula ${CH}_3{COOONO}_2$, is:
ⓐ. Peroxyacetyl Nitrate (${PAN}$)
ⓑ. Acrolein
ⓒ. Formaldehyde
ⓓ. Nitric Acid (${HNO}_3$)
Correct Answer: Peroxyacetyl Nitrate (${PAN}$)
Explanation: ${PAN}$ (Peroxyacetyl Nitrate) is a key secondary pollutant in photochemical smog. It is a potent lacrimator (causes tears) and is phytotoxic, causing significant damage to plant foliage.
265. Nitric Oxide (${NO}$) plays a catalytic role in the depletion of ozone within the stratosphere, according to the reaction ${NO} + {O}_3 \rightarrow {NO}_2 + {O}_2$. In this cycle, the ${NO}_2$ then reacts with an oxygen atom (${O}$) to regenerate the catalyst ${NO}$, completing the cycle. This cycle converts ozone into:
ⓐ. Nitrogen Pentoxide (${N}_2{O}_5$)
ⓑ. Molecular Oxygen (${O}_2$)
ⓒ. Nitrous Oxide (${N}_2{O}$)
ⓓ. Hydroxyl Radical (${OH}^{\\bullet}$)
Correct Answer: Molecular Oxygen (${O}_2$)
Explanation: The overall effect of the catalytic cycle is ${O}_3 + {O} \rightarrow 2{O}_2$. Both ${NO}$ and ${NO}_2$ are regenerated at the end of the two-step cycle, meaning the ozone is ultimately converted into two molecules of molecular oxygen (${O}_2$).
266. A method of solid waste disposal that involves the thermal decomposition of organic material at high temperatures (typically $400^{\circ}{C}$ to $850^{\circ}{C}$) in the complete absence of oxygen is known as:
ⓐ. Pyrolysis
ⓑ. Incineration
ⓒ. Bio-methanation
ⓓ. Anaerobic digestion
Correct Answer: Pyrolysis
Explanation: Pyrolysis is a thermochemical process that yields solid residue (char) and hydrocarbon gases/oils. It is distinct from incineration (which requires oxygen) and anaerobic digestion (which occurs at lower temperatures using microbes).
267. Which of the following is an effective strategy for controlling the emission of Sulphur Dioxide (${SO}_2$) from large industrial sources like coal-fired power plants?
ⓐ. Using catalytic converters at the end of the smokestack.
ⓑ. Mixing the coal with excess oxygen during combustion.
ⓒ. Cooling the combustion exhaust gases rapidly.
ⓓ. Flue Gas Desulphurization (${FGD}$) using lime (${CaO}$) scrubbers.
Correct Answer: Flue Gas Desulphurization (${FGD}$) using lime (${CaO}$) scrubbers.
Explanation: Flue Gas Desulphurization (${FGD}$) involves scrubbing the exhaust gases (flue gas) with a slurry containing a calcium compound (like lime or limestone) to chemically absorb and neutralize the ${SO}_2$, forming gypsum (${CaSO}_4\cdot 2{H}_2{O}$).
You are now on Class 11 Chemistry MCQs – Chapter 14: Environmental Chemistry (Part 3). This final section wraps up the chapter with the last 67 MCQs on advanced topics like buffer solutions and real-life applications of environmental chemistry in sustainability and pollution management.
- 👉 This page: Final 67 MCQs with answers and explanations
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