Miscellaneous: UPSC Previous Year Questions (Science and Technology)

Explanation

Alternative Powertrain Vehicles: Vehicles using propulsion systems other than conventional petrol or diesel internal combustion engines (ICEs), focusing on sustainable transport via electricity, hydrogen, or hybrid systems. Full Battery Electric Vehicles (BEVs): Powered solely by electricity in rechargeable battery packs, using electric motors, no ICE, fuel tank, or exhaust. Key Features:

Zero tailpipe emissions, reducing environmental impact. Efficiency depends on electricity source (renewable vs. fossil fuels). Examples: Tesla Model 3 (2017), Tata Nexon EV (2020). Hydrogen Fuel Cell Vehicles (FCEVs): They generate electricity via hydrogen-oxygen electrochemical reaction in fuel cell stack, powering electric motors; emit water vapor, heat. Key Features:

Zero-emission, suited for long-range, heavy-duty applications with fast refueling. Examples: Toyota Mirai (2014), Hyundai Nexo (2018). Fuel Cell Electric Hybrid Vehicles (FCE-HVs): They integrate hydrogen fuel cells and rechargeable batteries to power electric motors, using regenerative braking (turns kinetic energy into electricity by reversing the process that drives the car forward.) Key Features:

Combine fuel cell range, battery power for efficiency. Examples: Toyota, Honda prototypes (2020s). Hence, option (c) is correct.

Explanation

In electric vehicle lithium-ion batteries, cobalt, lithium, and nickel form cathodes determining energy density, lifespan, cost, and performance. Graphite is used exclusively in anodes, not cathodes. Electrolytes enable lithium ion movement, while separators prevent short circuits, allowing ion flow. Lithium-ion cell types are generally recognised by the cathode material. Some of the most common lithium-ion variants (based on cell chemistry) are NMC (Lithium nickel manganese cobalt), LFP (Lithium ferro (iron) phosphate), NCA (Lithium nickel cobalt aluminium oxide), LMO (Lithium manganese oxide) and LCO (Lithium cobalt oxide). Element-Wise Analysis Cobalt: Enhances thermal stability, extends lifespan in LCO, NMC, NCA. Used in smartphones, laptops (LCO), EVs Challenges: Expensive, toxic, 70% sourced from Democratic Republic of Congo (DRC), raising ethical concerns. Lithium: Critical for cathode (LiCoO₂, LiNiMnCoO₂, LiNiCoAlO₂, LiFePO₄) and electrolyte. Enables high voltage, sourced from Lithium Triangle (Chile, Argentina, Bolivia) and Australia. Nickel: Boosts energy density, range in NMC, NCA (80% of EV battery capacity, 2021). Supplied by Indonesia, Russia, Philippines. Challenge: Reduces thermal stability, needs cobalt, manganese. Graphite: Exclusive to anodes (28% of EV battery minerals), not cathodes. Natural/synthetic graphite intercalates lithium ions for conductivity, stability. China dominates anode-grade graphite. Research explores silicon anodes. Hence, option (c) is correct.

Explanation

Ethanol and urea can be produced via coal gasification, while nitroglycerine is not practically produced due to the lack of a viable glycerol synthesis pathway from syngas. Coal Gasification: It is a thermochemical process that converts coal into syngas (synthesis gas), a mixture of carbon monoxide (CO), hydrogen (H₂), carbon dioxide (CO₂), and methane (CH₄), through partial oxidation with oxygen and steam under high temperature (1000°C or more) and pressure. Syngas serves as a versatile chemical feedstock for producing fuels, fertilizers, and chemicals, supporting India’s National Coal Gasification Mission (2021) to gasify 100 million tonnes of coal by 2030 to reduce imports of natural gas, urea, and methanol. Ethanol: Production via Coal Gasification Process: Ethanol (CHOH) is produced from syngas through catalytic conversion (e.g., Fischer-Tropsch synthesis with rhodium-based catalysts) or microbial fermentation (e.g., using Clostridium ljungdahlii). Relevance: Syngas provides carbon monoxide and hydrogen, which are converted to ethanol as part of coal-to-liquids (CTL) processes. This supports India’s 20% ethanol blending policy (G20 Biofuel Policy) to reduce crude oil imports. Nitroglycerine: Feasibility via Coal Gasification Process: Nitroglycerine (CHNO), an explosive and pharmaceutical vasodilator, is produced by nitrating glycerol with nitric acid and sulfuric acid under controlled conditions. Relevance to coal gasification:

Syngas can produce hydrogen for ammonia via the Haber-Bosch process, which is used to make nitric acid. However, glycerol synthesis from syngas (e.g., via methanol-to-olefins or propylene pathways) is commercially unviable and not documented in coal gasification applications. While syngas can indirectly support nitric acid production, the glycerol required for nitroglycerine is not practically derived from coal gasification, making the process infeasible for industrial use. Urea: Production via Coal Gasification Process: Urea (CO(NH₂)₂) is produced by reacting ammonia (NH₃) with carbon dioxide (CO₂), both derivable from syngas. Hydrogen from syngas is used in the Haber-Bosch process to produce ammonia. Carbon monoxide in syngas is converted to CO via the water-gas shift reaction (CO + H₂O → CO₂ + H₂).

Explanation

Rare earth elements (REEs) are a group of 17 chemically similar metallic elements that are known for their high luster, high density, and unique magnetic, phosphorescent, and catalytic properties.

Statement 1 is correct: Rare earth elements such as europium, terbium, and yttrium are crucial for producing the bright, vivid colors in modern flat screens and monitors.

Statement 2 is correct: Many rare earth elements, like europium and terbium, have phosphorescent or luminescent properties, meaning they can absorb energy and emit light, which is used in various applications including displays.