Chemistry: Organic Chemistry: UPSC Previous Year Questions (Science and Technology)

Explanation

Option (d) is correct: Nitroglycerine is a highly explosive compound, commonly used in the production of dynamite. It is a liquid with high sensitivity to shock and heat, making it a powerful and widely used explosive in mining and demolition. Options (a), (b) and (c) are incorrect:

Phosphorus Trichloride is a chemical used in the manufacture of pesticides, not an explosive. Mercuric Oxide is an oxidizing agent used in batteries and chemical synthesis, not explosive. Graphite is a form of carbon used in lubricants and as an electrode material, not an explosive.

Explanation

Bisphenol A (BPA) is an industrial chemical extensively used in the production of polycarbonate plastics and epoxy resins. Polycarbonate plastics made using BPA are commonly employed in the manufacture of reusable water bottles, food containers, and baby bottles due to their durability and lightweight properties. Epoxy resins containing BPA are used as coatings for the inside of food and beverage cans to prevent corrosion and contamination. However, BPA is a controversial substance because it can leach into food and beverages under high temperatures or prolonged storage. It is considered a potential endocrine disruptor that may interfere with hormonal activity, prompting regulatory bodies worldwide to evaluate its safety in food-related applications.

Explanation

Methane and air are responsible for mine explosions, often referred to as fire damp explosions. Methane (CH₄) is a flammable gas that accumulates in coal mines. When mixed with air in the presence of a spark, it can cause deadly explosions. Options (a), (b) and (d) are incorrect:

While Hydrogen and Oxygen are explosive, these gases are not significantly common in mining environments. Oxygen and Acetylene are used in welding, not relevant to mine explosions. Carbon Dioxide and Methane: Carbon dioxide is inert and cannot contribute to mine explosions.

Explanation

Option (d) is correct: Cyclonite is another name for RDX (Research Department Explosive or Royal Demolition Explosive), which is a powerful military-grade explosive. It is widely used in military applications and mining operations due to its high detonation velocity and stability. Options (a), (b) and (c) are incorrect:

Cyanohydrin is a type of organic compound used in the synthesis of plastics and pharmaceuticals, not an explosive. Dextran is a complex sugar used in medical applications like blood volume expanders. Cyclohexane is a hydrocarbon commonly used as a solvent or in chemical synthesis, not an explosive.

Explanation

Option 1 is correct: Benzene was used in the past for dry cleaning but has been largely discontinued due to its toxicity and carcinogenicity.

Option 2 is correct: Carbon tetrachloride was commonly used for dry cleaning in earlier times but has been replaced by safer alternatives due to environmental concerns.

Option 3 is incorrect: Sodium carbonate (washing soda) is not typically used in dry cleaning; it is more commonly used in laundry detergents and cleaning solutions.

Option 4 is correct: Trichloroethylene is widely used as a dry cleaning solvent due to its ability to dissolve oils, greases, and waxes without damaging fabrics.

Explanation

LNG is natural gas that has been cooled to a liquid form, making it easier to transport across long distances where pipelines are not feasible. Liquefied Natural Gas (LNG) and Natural Gas Liquids (NGL) play crucial roles in the global energy market, facilitating the storage, transportation, and consumption of natural gas.

Statement 1 is correct: LNG is natural gas cooled to approximately -162°C at normal atmospheric pressure, making it a liquid for ease of storage and transportation in specialized cryogenic tanks.

Statement 2 is incorrect: The first LNG terminal in India was built at Dahej, Gujarat, not Hassan.

Statement 3 is correct: Natural Gas Liquids (NGLs), such as ethane, propane, butane, and natural gasoline, are extracted from natural gas and can be separated from LPG.

Explanation

Detergents are cleaning agents used to remove dirt, grease, and stains from surfaces and fabrics. Key additives like sodium sulphate prevent clumping by keeping the powder dry, while sodium silicate maintains alkalinity, enhancing the cleaning efficiency.

Statement 1 is correct: Sodium sulphate is added to keep the washing powder dry by preventing it from absorbing moisture.

Statement 2 is correct: Sodium silicate is used to maintain the alkalinity of the detergent, which enhances the cleaning action by breaking down grease and dirt.

Explanation

A is matched with 2: Cracking is a process in the petroleum industry where large hydrocarbons are broken into smaller hydrocarbons like gasoline and diesel. B is matched with 3:Smelting is used in the copper industry to extract metal from its ore by heating it in a furnace. C is matched with 4: Hydrogenation is used in the production of edible fats by adding hydrogen to vegetable oils, converting them into margarine or vanaspati. D is matched with 1: Vulcanization is a process in the rubber industry where sulfur is added to raw rubber to improve its elasticity and strength.

Explanation

Assertion A is true: Phenyl, a common household germicide, contains phenol derivatives that disrupt bacterial cell membranes and denature proteins, making it effective against germs. Reason R is true: Phenol, also called carbolic acid, is a well-known antiseptic and disinfectant due to its ability to kill bacteria, fungi, and viruses. This explains the germicidal property of phenyl. Thus, both Assertion (A) and Reason (R) are true, and R correctly explains A.

Explanation

The distinctive pungent odour of garlic is due to sulphur-containing compounds, mainly allicin. These compounds are formed when alliin is converted by the enzyme alliinase during chopping or crushing.