================================== DOCUMENT 4: SESSION 7 (S7) ================================== POLLUTION ABATEMENT (21CHO105T) Unit 1 - Session 7 I. MULTIPLE CHOICE QUESTIONS (MCQs) 1. Which method improves reaction efficiency and reduces waste? ● Answer: B) Catalysis ● Explanation: Catalysts increase reaction rates and product selectivity, lower required activation energy, and enable reactions to proceed under milder conditions, minimizing waste generation. 2. Which of the following feedstocks is renewable? ● Answer: D) Plant biomass ● Explanation: Plant biomass is replenishable on human timescales, unlike finite fossil fuel resources such as coal, petroleum, and natural gas. 3. Which technique reduces solvent use in chemical reactions? ● Answer: A) Solid-state reactions ● Explanation: Solvent-free or solid-state reactions carry out chemical transformations without organic solvents, eliminating volatile organic compound (VOC) emissions and solvent recovery steps. 4. Which process reduces hazardous by-products? ● Answer: A) High atom economy reactions ● Explanation: High atom economy maximizes the incorporation of all raw material atoms into the desired final product, minimizing unwanted by-products. 5. Which energy source is most environmentally friendly? ● Answer: B) Solar energy ● Explanation: Solar energy is a renewable, zero-emission resource during power generation, replacing fossil fuels like coal, diesel, and petrol. II. SHORT ANSWER QUESTIONS 1. What is meant by an environment-friendly chemical process? ● Answer: An environment-friendly chemical process (or green chemical process) is a chemical manufacturing approach designed to minimize or eliminate the generation of hazardous substances, optimize atom efficiency, lower energy usage, and utilize renewable feedstocks throughout design, synthesis, and application. 2. Why are renewable feedstocks important in green chemistry? ● Answer: ○ Resource Preservation: Replaces depleting petroleum and fossil fuel reserves with bio-based materials (e.g., agricultural waste, biomass). ○ Carbon Neutrality: Bio-based feedstocks recycle contemporary atmospheric carbon via biological carbon cycles rather than adding subterranean fossil carbon into the carbon cycle. III. LONG ANSWER QUESTION 1. Discuss the principles and advantages of environment-friendly chemical processes. ● Answer: 1. Core Principles of Environment-Friendly Chemical Processes ● Waste Prevention: Designing chemical syntheses to prevent waste generation prior to production rather than treating or cleaning up waste after formation. ● Atom Economy: Maximizing the efficiency of chemical processes by designing reactions where maximum reactant atoms are conserved in the target product: $$\text{Percent Atom Economy} = \left( \frac{\text{Molecular Weight of Desired Product}}{\text{Total Molecular Weight of All Reactants}} \right) \times 100\%$$ ● Less Hazardous Chemical Syntheses: Selecting synthetic methods that utilize and produce substances with minimal toxicity to human health and natural ecosystems. ● Design for Energy Efficiency: Conducting chemical reactions at ambient temperature and pressure parameters whenever possible to reduce thermal energy demands. ● Use of Renewable Feedstocks: Prioritizing agricultural and biological waste materials over non-renewable fossil fuel inputs. ● Catalytic vs. Stoichiometric Reagents: Employing catalytic reagents that can be reused, avoiding consumption of stoichiometric amounts of reagents. 2. Practical Industrial Applications ● Supercritical Fluids: Utilizing supercritical carbon dioxide ( ) as a non-toxic 𝑠𝑐𝐶𝑂 2 alternative to halogenated organic solvents in extraction and synthesis. ● Biocatalysis: Applying enzymatic catalysts for highly specific transformation steps in pharmaceutical production under aqueous conditions. 3. Environmental and Economic Advantages ● Reduced Eco-toxicity: Significant decreases in hazardous chemical spills, volatile organic compound (VOC) emissions, and hazardous waste disposal burdens. ● Cost Efficiency: Lower raw material consumption, reduced energy expenditures, and decreased hazardous waste treatment costs. ● Enhanced Industrial Safety: Lower operational pressure/temperature regimes reduce explosive hazards and workplace toxic exposures.