180. Which greenhouse gas is produced when fossil fuels burn?
[WBCS Mains 2021 — held May 2022, Paper IV]
(A) Methane
(B) Carbon monoxide
(C) Hydrogen
(D) Carbon dioxide
Answer: (D) Carbon dioxide
Explanation: Complete combustion of hydrocarbon fuels converts carbon into carbon dioxide and hydrogen into water. Carbon dioxide absorbs outgoing infrared radiation and contributes to the greenhouse effect. Incomplete combustion may additionally release carbon monoxide and soot, depending on the available oxygen.
179. Which crop is a major anthropogenic source of both methane and nitrous oxide?
[UPSC CSE Prelims — 05 Jun 2022]
(A) Cotton
(B) Rice
(C) Sugarcane
(D) Wheat
Answer: (B) Rice
Explanation: Flooded paddy fields create low-oxygen soil conditions in which microbes generate methane. Nitrogen transformations in fertilised soils can also release nitrous oxide. This is why rice cultivation is discussed in greenhouse-gas inventories for agriculture and climate change.
178. Which compound is the principal component of natural gas?
[UPPCS Prelims — 12 Jun 2022]
(A) Butane
(B) Hexane
(C) Benzene
(D) Methane
Answer: (D) Methane
Explanation: Natural gas consists mainly of methane, the simplest hydrocarbon with formula CH₄. It may also contain smaller amounts of ethane, propane, heavier hydrocarbons and non-combustible gases. Because methane is combustible and widely distributed, natural gas is an important fuel and chemical feedstock.
177. In which form is the chemical compound RDX used?
[HSSC Police Constable — 07 Aug 2021, Shift 1]
(A) As a composition
(B) As a reactor
(C) As an explosive
(D) As a nuclear weapon
Answer: (C) As an explosive
Explanation: RDX is classified as an energetic organic compound used as an explosive, not a reactor or a nuclear weapon. It is also known as cyclonite or hexogen. Such questions assess the general identification of a chemical substance.
176. Consider furnace oil:
1. It is a refinery product.
2. Industries use it to generate power.
3. Its use can release sulphur pollutants.
Which statements are correct?
[UPSC CSE Prelims — 10 Oct 2021]
(A) 1 and 2 only
(B) 2 and 3 only
(C) 1 and 3 only
(D) 1, 2 and 3
Answer: (D) 1, 2 and 3
Explanation: Furnace oil is obtained during petroleum refining and is commonly burned to provide industrial heat or power. Its sulphur-containing constituents may yield sulphur dioxide during combustion, creating pollution concerns. Therefore all three stated characteristics are correct for typical furnace oil.
175. Which organisation is the largest producer of crude oil and natural gas in India?
[RRB NTPC CBT-I — 05 Apr 2021, Shift 1]
(A) NTPC
(B) SAIL
(C) BHEL
(D) ONGC
Answer: (D) ONGC
Explanation: ONGC is a major government-owned exploration and production company for India’s crude oil and natural gas resources. Crude oil is refined into many hydrocarbon fuels and petrochemical feedstocks. Its dominant role in domestic extraction distinguishes it from the other listed public-sector companies.
174. Which combinations were identified for conversion of benzene into benzaldehyde?
I. CO/HCl/AlCl₃/Cu₂Cl₂;
II. Zn(CN)₂/HCl followed by hydrolysis;
III. HCHO/HCl/AlCl₃;
IV. DMF/POCl₃ conditions.
[UPPSC GIC Lecturer Chemistry — 2021]
(A) I, II and III only
(B) I, II and IV only
(C) II, III and IV only
(D) All four
Answer: (B) I, II and IV only
Explanation: Gattermann–Koch formylation introduces a formyl group onto an aromatic ring; other specified formylation methods can also be applied in the source examination’s scheme. Formaldehyde and hydrogen chloride instead favour chloromethylation, so set III does not directly produce benzaldehyde.
173. Evaluate:
I. Aspirin and paracetamol are narcotic analgesics.
II. Morphine and heroin are non-narcotic analgesics.
[NEET Chemistry — 2021]
(A) Only II is correct
(B) Both statements are correct
(C) Neither statement is correct
(D) Only I is correct
Answer: (C) Neither statement is correct
Explanation: Aspirin and paracetamol are non-narcotic analgesics used for mild to moderate pain and fever. Morphine and heroin belong to the opioid or narcotic class instead. The statements reverse both classifications, so neither is correct under the examination’s terminology.
172. Who among the following scientists invented dynamite?
[SSC CHSL — 18 Mar 2020, Shift 1]
(A) Alfred Nobel
(B) Thomas Alva Edison
(C) Rudolf Diesel
(D) Benjamin Franklin
Answer: (A) Alfred Nobel
Explanation: Alfred Nobel invented dynamite during the nineteenth century, and his name later became associated with the Nobel Prizes. Edison is linked to electrical inventions, Diesel to the diesel engine, and Franklin to early electrical research.
171. LPG is chiefly a mixture of which gases?
[WBCS Prelims — 2020]
(A) Methane and butane
(B) Propane and butane
(C) Ethane and propane
(D) Ethane and butane
Answer: (B) Propane and butane
Explanation: Liquefied petroleum gas mainly consists of propane and butane, both saturated hydrocarbons. They liquefy relatively easily under pressure, supporting cylinder storage and transport. Natural gas, by contrast, is dominated by methane and is generally distributed through pipelines or as CNG.
