Why Correct: LPG has a calorific value of approximately 50 MJ/kg, which is significantly higher than many other common fuels. This high energy density makes it efficient for cooking and heating applications as it provides substantial energy per unit mass.
Distractor Analysis: 25 MJ/kg is closer to the calorific value of coal, 35 MJ/kg is typical for some petroleum products but lower than LPG, and 65 MJ/kg exceeds the actual value for LPG.
Takeaway: The high calorific value of LPG (around 50 MJ/kg) combined with its ability to be stored as a liquid under pressure and vaporize upon release makes it an efficient and practical fuel for domestic and industrial use.

Why Correct: Methane (CH₄) is the principal component of Compressed Natural Gas (CNG), which is widely used as a vehicular fuel due to its lower emissions compared to gasoline or diesel.
Distractor Analysis: Ethane (C₂H₆) is a minor constituent in natural gas but not the main fuel component. Propane (C₃H₈) and butane (C₄H₁₀) are key constituents of LPG, not CNG.
Takeaway: CNG, rich in methane, offers advantages like higher auto-ignition temperature and lower carbon dioxide emissions per unit energy, making it a preferred choice for reducing urban air pollution.

Why Correct: Ethane (C₂H₆) is a significant byproduct of petroleum refining and natural gas processing. It's primarily used as a feedstock in steam crackers to produce ethylene, which is the building block for many plastics and chemicals. Distractor Analysis: Methane (CH₄) is the main component of natural gas but not typically a major byproduct of petroleum cracking. Propane (C₃H₈) and butane (C₄H₁₀) are components of LPG but are less important than ethane as ethylene feedstocks. Takeaway: Ethane's industrial importance lies in its role as a primary raw material for ethylene production through thermal cracking processes.

Why Correct: Ethyl mercaptan (ethanethiol) is added to LPG as an odorant because LPG itself is odorless. This strong, unpleasant smell helps detect leaks and prevents accidents.
Distractor Analysis: LPG has a high calorific value of about 50 MJ/kg due to its hydrocarbon composition. The auto-ignition temperature of LPG ranges from 410-580°C, which is higher than petrol's 246-280°C. LPG is heavier than air with a density of about 2.01 kg/m³, causing it to settle in low areas during leaks.
Takeaway: CNG (Compressed Natural Gas) also receives odorant additives, typically tetrahydrothiophene or mercaptans, for the same safety purpose.

Why Correct: LPG has a density of about 2.01 kg/m³, which is higher than air's 1.225 kg/m³. This causes LPG to accumulate near the ground during leaks, creating a fire hazard in confined spaces.
Distractor Analysis: LPG's calorific value is approximately 50 MJ/kg, making it more energy-dense than many fuels. The auto-ignition temperature of LPG ranges from 410-580°C, affecting combustion safety. Propane is a significant component of LPG but does not determine its density relative to air.
Takeaway: CNG primarily contains methane and has a lower density than air, causing it to rise and disperse quickly during leaks.

Why Correct: LPG has an auto-ignition temperature of 410-580°C. This is significantly higher than petrol's 246-280°C and diesel's 210°C.
Distractor Analysis: Petrol ignites at 246-280°C under compression in engines. Diesel auto-ignites around 210°C in compression ignition systems. CNG (methane) auto-ignites at approximately 540°C, still lower than LPG's maximum range.

Why Correct: Walter Snelling, an American chemist, first developed the commercial process for liquefying petroleum gases around 1910 while working for the U.S. Bureau of Mines.
Distractor Analysis: Robert Bunsen invented the Bunsen burner and made contributions to gas analysis. Humphry Davy invented the miner's safety lamp and discovered several elements. Michael Faraday discovered benzene and made fundamental contributions to electromagnetism.

Why Correct: LPG liquefies under moderate pressure of 2-8 bar for storage and transport. CNG remains a compressed gas at much higher pressures, typically 200-250 bar.
Distractor Analysis: CNG requires high-pressure storage, not LPG. CNG primarily contains methane, not propane and butane. CNG has a higher ignition temperature than LPG.
Takeaway: The primary source of LPG is petroleum refining and natural gas processing, making it a byproduct of hydrocarbon industries.

Why Correct: Propane boils at -42°C, while butane boils at -0.5°C. This lower boiling point allows propane to vaporize more readily in cold temperatures, ensuring consistent fuel supply.
Distractor Analysis: Ignition temperature affects safety but not cold-weather performance. Density influences storage but not vaporization. Carbon content relates to energy output, not climate suitability.

Why Correct: Propane has a lower boiling point (-42°C) than butane (-0.5°C). This ensures better vaporization and consistent gas supply in cold winter temperatures.
Distractor Analysis: Production costs are not the primary factor in seasonal LPG blending. Combustion efficiency depends on complete oxidation, not seasonal composition. LPG density remains heavier than air regardless of propane-butane ratio.
Takeaway: Summer LPG blends contain more butane, which has higher energy content per unit volume and is more economical in warmer conditions.

Why Correct: Butane and isobutane are structural isomers. They share the same molecular formula C4H10 but differ in the arrangement of carbon atoms in their skeletal structure.
Distractor Analysis: Functional isomers have different functional groups despite the same molecular formula. Geometrical isomers arise from restricted rotation around double bonds or rings. Chain isomers are a subtype of structural isomers specifically involving different carbon chain arrangements.
Takeaway: Structural isomerism includes chain, position, and functional isomerism as its main categories in organic chemistry.

Why Correct: Propane has a lower boiling point of -42°C compared to butane's -0.5°C. This allows propane to vaporize more readily in cold winter temperatures.
Distractor Analysis: Calorific value measures energy content per unit mass. Density affects how gases disperse in air. Flash point indicates the lowest temperature at which vapors ignite.
Takeaway: Winter LPG blends typically contain 50-60% propane to ensure adequate vapor pressure for appliance operation in cold climates.

Why Correct: CNG contains 85-95% methane, making it the primary component that differentiates it from LPG.
Distractor Analysis: Butane and propane are the main components of LPG, not CNG. Ethane is a minor component present in both natural gas and LPG in small quantities.
Takeaway: CNG is stored at high pressure (200-250 bar) as a gas, while LPG is stored under moderate pressure as a liquid.

Why Correct: LPG has a density approximately 1.5-2.0 times that of air. This causes leaked LPG to accumulate at ground level in low-lying areas, creating explosive mixtures that require proper ventilation for safety.
Distractor Analysis: LPG's high calorific value of 46-50 MJ/kg makes it an efficient fuel but doesn't directly cause accumulation hazards. LPG is indeed colorless but this property doesn't affect its accumulation behavior. LPG has an ignition temperature around 450-500°C, which is comparable to many other hydrocarbon fuels.
Takeaway: Ethyl mercaptan (ethanethiol) is added to LPG at 10-50 ppm concentrations specifically to give it a distinctive rotten egg smell for leak detection.