15 previous year UPSC Prelims questions on organic chemistry appear here, from 1996 to 2009. UPSC asks which compound is an explosive, what RDX and Bisphenol A are, what causes mine explosions and why builders are added to detergents. The explanations give the use and hazard of each substance.
Explanations state facts as of the year each question was asked; words like “recently” refer to that year.
Showing 11–15 of 15 questions
Eugenol is the active component in clove oil, contributing to its distinct aroma and analgesic properties. It is widely used in dental care and as a natural preservative.
Mustard gas (sulfur mustard) was widely used as a chemical weapon during World War I. It causes blistering of the skin and mucous membranes, along with severe respiratory damage.
Option (a) is correct: Hydrogen has the highest calorific value of around 120-150 MJ/kg, making it an efficient and eco-friendly fuel. Combustion of hydrogen produces only water, contributing to clean energy initiatives. Options (b), (c) and (d) are incorrect:
Charcoal: Has a calorific value of 30 MJ/kg(approx.), significantly lower than hydrogen. Natural gas: Primarily composed of Methane, With a fuel value of around 55 MJ/kg(approx.), it is lower than hydrogen but widely used due to availability. Gasoline: Though energy-dense around 47 MJ/kg (approx.), but lower than hydrogen.
Option (d) is correct: Ethylene glycol is a widely used anti-freeze for automobile engines. It effectively lowers the freezing point of the coolant, preventing it from freezing in cold climates. Additionally, it raises the boiling point of the coolant, ensuring efficient heat transfer during engine operation. Options (a), (b) and (c) are incorrect:
Propyl alcohol is rarely used as an anti-freeze due to its lower efficiency and higher cost compared to ethylene glycol. While ethanol has some anti-freeze properties, it is volatile and less efficient than ethylene glycol. Although methanol can be used as an anti-freeze, it is highly toxic and less efficient compared to ethylene glycol.
Option (d) is correct: Methyl alcohol (methanol) is a highly toxic substance that is sometimes illegally added to liquor to reduce costs. Once consumed, it metabolizes into formaldehyde and formic acid, causing blindness, organ failure, or death. Symptoms of methanol poisoning include blurred vision, nausea, and seizures. Options (a), (b) and (c) are incorrect:
Ethyl alcohol is commonly known as ethanol, it is the primary component in alcoholic beverages and is safe for consumption in moderate amounts. Amyl alcohol is found in some industrial applications, amyl alcohol is rarely used in adulterated liquor due to its cost and limited availability. Benzyl alcohol is a non-toxic solvent and not associated with blindness in liquor tragedies. It is used in pharmaceuticals and cosmetics.
| Q | UPSC year | Correct answer |
|---|---|---|
| 11 | 1997 | (b) Eugenol |
| 12 | 1997 | (c) Mustard gas |
| 13 | 1997 | (a) Hydrogen |
| 14 | 1997 | (d) Ethylene glycol |
| 15 | 1996 | (d) methyl alcohol |
This page covers 15 previous year UPSC Prelims GS Paper-I questions on Chemistry: Organic Chemistry (Science and Technology), asked from 1996 to 2009. Each has the correct answer and an explanation.
A powerful explosive, also called Cyclonite or Hexogen, used in military and demolition work. It is a white crystalline solid that is more powerful than TNT, and is often combined with other explosives.
A mixture of methane and air, known as firedamp. Methane released from coal seams forms an explosive mixture with air, and a spark or flame can ignite it, which is why mines are ventilated.
A chemical used to make polycarbonate plastics and epoxy resins, found in bottles and food-can linings. It has been linked to hormone-disrupting effects, which is why its use in baby bottles is restricted in many places.
