Organic Chemistry

VidyaarOctober 22, 20260413 views

The collection includes hydrocarbons, alcohols, polymers, organic acids, explosive substances, fuels, and related organic chemistry topics.

280. Unsaturated hydrocarbons usually produce:

[RRB Group D — 10 Feb 2026, Shift 2]

(A) Yellow flame with black smoke

(B) Clean blue flames

(D) No flame at all

Answer: (A) Yellow flame with black smoke

Explanation: Unsaturated hydrocarbons contain carbon–carbon double or triple bonds. In ordinary air they tend to burn with a luminous, smoky flame when combustion is incomplete. Soot consists of fine carbon particles, whereas complete combustion chiefly yields carbon dioxide and water.

279. Which property of carbon allows it to form a large number of compounds by bonding with itself and other elements?

[RRB Group D — 10 Feb 2026, Shift 2]

(A) Catenation

(B) Tetravalency

(D) Isomerism

Answer: (A) Catenation

Explanation: Catenation is the capacity of carbon atoms to link to other carbon atoms through stable covalent bonds. Together with tetravalency, it enables long chains, branches and rings. This structural variety explains the enormous number of organic compounds.

278. Baking soda releases which gas on heating?

[RRB Group D — 09 Feb 2026, Shift 2]

(A) CO₂

(B) H₂

(D) O₂

Answer: (A) CO₂

Explanation: Sodium hydrogen carbonate decomposes on heating into sodium carbonate, water vapour and carbon dioxide. The released gas contributes to the rising of baked products. Although baking soda is an inorganic salt, its reactions are relevant to organic food acids.

277. Which of the following is a straight-chain saturated hydrocarbon?

[RRB Group D — 06 Feb 2026, Shift 1]

(A) Butane

(B) Cyclohexane

(D) Benzene

Answer: (A) Butane

Explanation: Butane has four carbon atoms joined in an unbranched chain by single covalent bonds. Cyclohexane is cyclic, propene contains a double bond, and benzene is aromatic. Straight-chain alkanes have the general molecular formula CnH2n+2.

276. A molecule of methane contains one carbon atom bonded to four hydrogen atoms. What is the chemical formula for methane?

[RRB Group D — 06 Feb 2026, Shift 1]

(A) C₄H

(B) CH₄

(D) C₂H₄

Answer: (B) CH₄

Explanation: Methane is the simplest alkane. Its one carbon atom shares electrons with four hydrogen atoms, forming four single covalent bonds. The formula CH₄ also reflects the tetravalency of carbon and methane’s importance as the principal constituent of natural gas.

275. Statement A: Carboxylic acids are strong acids that completely ionise in water.
Statement B: Ethanoic acid is a weak acid compared to hydrochloric acid.

Select the correct option.

[RRB Group D — 05 Feb 2026, Shift 3]

(A) Both A and B are correct

(B) A is incorrect but B is correct

(D) A is correct but B is incorrect

Answer: (B) A is incorrect but B is correct

Explanation: Ethanoic acid is a weak organic acid because only a small fraction ionises in aqueous solution. Hydrochloric acid is much more extensively ionised at comparable concentrations. Therefore, the assertion about all carboxylic acids being strong is false.

274. Which of the following is a ring-chain hydrocarbon?

[RRB Group D — 05 Feb 2026, Shift 2]

(A) Propane

(B) Benzene

(D) Heptyne

Answer: (B) Benzene

Explanation: Benzene contains six carbon atoms joined in a cyclic aromatic structure. Propane, ethene and heptyne have open-chain arrangements. Benzene’s delocalised pi electrons distinguish its reactions from those of ordinary alkenes, even though both contain unsaturation.

273. What are the primary products formed during the complete combustion of most carbon compounds?

[RRB Group D — 05 Feb 2026, Shift 1]

(A) Carbon monoxide and water

(B) Carbon dioxide, water, and energy

(D) Soot and carbon dioxide

Answer: (B) Carbon dioxide, water, and energy

Explanation: When sufficient oxygen is supplied, carbon in a combustible organic compound is oxidised mainly to carbon dioxide and hydrogen to water. Combustion also releases energy, commonly as heat and light. Oxygen deficiency may instead produce soot or carbon monoxide.

272. Which of the following is an example of a cyclic hydrocarbon?

[RRB Group D — 05 Feb 2026, Shift 1]

(A) Methane

(B) Butane

(D) Ethene

Answer: (C) Cyclohexane

Explanation: Cyclohexane is a saturated ring containing six carbon atoms and has the formula C₆H₁₂. Methane has one carbon atom, butane is an open-chain alkane, and ethene is an open-chain alkene with a carbon–carbon double bond.

271. Which of the following is true about the homologous series?

[RRB Group D — 05 Feb 2026, Shift 1]

(A) Each successive member differs by a –CH₂– group

(B) All members have different functional groups

(D) All members have the same boiling point

Answer: (A) Each successive member differs by a –CH₂– group

Explanation: Consecutive members of a homologous series differ by one methylene unit, CH₂, equivalent to 14 atomic mass units. They share a functional group and therefore show related chemical properties, while physical properties generally vary gradually with molecular size.

270. What is typically involved in an addition reaction?

[RRB Group D — 04 Feb 2026, Shift 3]

(A) Functional groups are replaced by others

(B) Removal of atoms from molecules takes place

(D) Oxidation changes without new bonding

Answer: (C) Atoms get added to unsaturated bonds

Explanation: Addition reactions characteristically occur across carbon–carbon double or triple bonds. During the reaction, the multiple bond’s pi component is broken while new sigma bonds form with incoming atoms or groups. Hydrogenation of alkenes is a familiar example.

269. Ethanoic acid reacts with ethanol in the presence of concentrated H₂SO₄ to form:

[RRB Group D — 04 Feb 2026, Shift 1]

(A) Ethyl ethanoate

(B) Methanol

(D) Sodium acetate

Answer: (A) Ethyl ethanoate

Explanation: Ethanoic acid reacts with ethanol through esterification to produce ethyl ethanoate and water. Concentrated sulphuric acid catalyses the reaction. Ethyl ethanoate is an ester with a characteristic fruity smell, and the process is reversible.

268. What is formed when ethanol is oxidised using an oxidising agent like alkaline KMnO₄?

[RRB Group D — 04 Feb 2026, Shift 1]

(A) Methane

(B) Methanoic acid

(D) Ethanoic acid

Answer: (D) Ethanoic acid

Explanation: Ethanol is a primary alcohol that can be oxidised first to ethanal and subsequently to ethanoic acid. Strong oxidising agents such as potassium permanganate commonly drive the conversion towards the carboxylic acid. Its carbon chain remains two atoms long.

267. Which of the following is a homologous series?

[RRB Group D — 03 Feb 2026, Shift 3]

(A) Methane, methanol, methanoic acid

(B) Ethene, ethyne, ethane

(D) Methane, ethane, ethene

Answer: (C) Methane, ethane, propane

Explanation: Methane, ethane and propane are successive members of the alkane family. Each next member adds a CH₂ group and all follow the general formula CnH2n+2. The other sets mix compounds from different functional or bond classes.

266. Carbon has the unique ability to form bonds with other carbon atoms, giving rise to large molecules. This property is called:

[RRB Group D — 03 Feb 2026, Shift 3]

(A) Addition

(B) Catenation

(D) Conjugation

Answer: (B) Catenation

Explanation: Catenation refers to self-linking among atoms of the same element. Carbon is particularly effective because its small atomic size permits strong carbon–carbon bonds. This allows the formation of stable chains and rings that underlie organic chemistry.

265. What is the primary characteristic that defines organic compounds?

[RRB Group D — 03 Feb 2026, Shift 1]

(A) They always contain oxygen

(B) They are formed only by living organisms

(D) They principally consist of carbon-based covalent structures

Answer: (D) They principally consist of carbon-based covalent structures

Explanation: Organic chemistry mainly investigates carbon compounds, particularly those with carbon–hydrogen bonds and covalent molecular frameworks. Organic compounds may also contain oxygen, nitrogen, sulphur or halogens. They need not originate in living organisms; many are synthesised industrially.

264. The reaction of an alcohol with ethanoic acid in the presence of a catalyst forms water and:

[RRB Group D — 02 Feb 2026, Shift 2]

(A) An aldehyde

(B) A hydrocarbon

(D) An ester

Answer: (D) An ester

Explanation: This is esterification, a condensation process in which an alcohol and a carboxylic acid yield an ester plus water. For ethanol and ethanoic acid, the product is ethyl ethanoate. An acid catalyst increases the reaction rate.

263. Statement A: Alcohols react with sodium to evolve hydrogen.
Statement B: No gas is evolved when sodium reacts with ethanol.

Choose the correct statement.

[RRB Group D — 02 Feb 2026, Shift 2]

(A) Both A and B are correct

(B) A is correct but B is incorrect

(D) A is incorrect but B is correct

Answer: (B) A is correct but B is incorrect

Explanation: Reactive sodium metal displaces the hydrogen of ethanol’s hydroxyl group, yielding sodium ethoxide and hydrogen gas. Hence the first statement is true and the second false. The result distinguishes alcohol chemistry from some reactions involving hydrocarbons.

262. Which alcohol is commonly used as fuel?

[RRB Group D — 09 Jan 2026, Shift 1]

(A) Butanol

(B) Ethanol

(D) Propanol

Answer: (B) Ethanol

Explanation: Ethanol is widely used as a renewable fuel and petrol-blending component. It can be produced through fermentation of sugars from biomass. Because it contains oxygen and burns readily, its addition to petrol can influence combustion characteristics and fossil-fuel use.

261. Select the example of a functional group that does not contain a double bond in its structure.

[RRB Group D — 09 Jan 2026, Shift 1]

(A) Propanone

(B) Propanol

(D) Propanoic acid

Answer: (B) Propanol

Explanation: Propanol is an alcohol containing a hydroxyl group with single carbon–oxygen bonding. Propanone, propanal and propanoic acid each possess a carbonyl C=O group. Therefore, among the choices, propanol lacks the double bond present in the other functional groups.

260. Esters are __________ substances.

[RRB Group D — 08 Jan 2026, Shift 2]

(A) Sweet-smelling

(B) Musty-smelling

(D) Bitter-smelling

Answer: (A) Sweet-smelling

Explanation: Many small, volatile esters possess pleasant, fruity or sweet odours. They are common ingredients in fragrances and flavour formulations. An ester typically contains the –COO– linkage and can form by reacting a carboxylic acid with an alcohol.

259. What type of gas is released when ethanol reacts with sodium?

[RRB Group D — 08 Jan 2026, Shift 1]

(A) Methane

(B) Carbon dioxide

(D) Hydrogen

Answer: (D) Hydrogen

Explanation: Sodium replaces the hydroxyl hydrogen of ethanol, forming sodium ethoxide and liberating hydrogen gas. The observation reflects the presence of the O–H bond in alcohols. It is not the usual reaction of a simple saturated hydrocarbon.

258. Which structural feature contributes to the high reactivity of unsaturated organic compounds?

[RRB Group D — 29 Dec 2025, Shift 3]

(A) Halogen atoms on the carbon framework

(B) Absence of all hydrogen atoms

(D) Double or triple bonds between carbon atoms

Answer: (D) Double or triple bonds between carbon atoms

Explanation: Unsaturation means a carbon–carbon double or triple bond. The associated pi bonds are susceptible to addition reactions and make such compounds more reactive toward certain reagents than corresponding alkanes. Saturated hydrocarbons contain only carbon–carbon single bonds.

257. Which of the following hydrocarbons contains a branched chain?

[RRB Group D — 27 Dec 2025, Shift 3]

(A) Butane

(B) Ethene

(D) Methane

Answer: (C) Isobutane

Explanation: Isobutane is the common name of 2-methylpropane, a branched structural isomer of butane. Both have the molecular formula C₄H₁₀ but differ in the arrangement of their carbon atoms. Branching can change physical properties such as boiling point.

256. Which of the following represents a straight-chain hydrocarbon?

[RRB Group D — 23 Dec 2025, Shift 2]

(A) Isobutane

(B) Benzene

(D) Butane

Answer: (D) Butane

Explanation: Normal butane consists of four consecutive carbon atoms with no side branch. Isobutane has a branched skeleton, while benzene and cyclopentane are ring compounds. Thus butane is the only straight-chain example among the available choices.

255. Why does carbon form covalent bonds in organic compounds?

[RRB Group D — 22 Dec 2025, Shift 1]

(A) It has a complete outer electron shell

(B) It readily forms positive ions

(D) It easily loses all its valence electrons

Answer: (C) It has four valence electrons and shares electrons to complete its octet

Explanation: Carbon possesses four valence electrons. Gaining or losing four electrons completely is energetically unfavourable, so it normally achieves stable bonding by sharing electron pairs. This explains the prevalence of covalent carbon–carbon and carbon–hydrogen bonds in organic substances.

254. Which of the following is a saturated hydrocarbon?

[RRB Group D — 17 Dec 2025, Shift 1]

(A) Butyne

(B) Ethene

(D) Propane

Answer: (D) Propane

Explanation: Propane belongs to the alkane homologous series and has only single carbon–carbon bonds. Butyne and ethyne contain triple bonds, while ethene contains a double bond. Propane therefore has the maximum hydrogen content compatible with its open-chain carbon skeleton.

253. What is the primary role of a functional group in an organic compound?

[RRB Group D — 16 Dec 2025, Shift 2]

(A) Change the chain from straight to branched

(B) Determine the physical state alone

(D) Increase molecular mass

Answer: (C) Provide characteristic chemical properties

Explanation: A functional group is the atom or group of atoms chiefly responsible for predictable chemical reactions of an organic molecule. Alcohols, aldehydes, ketones and carboxylic acids have different groups and therefore distinct reactivity, even when their carbon frameworks are similar.

252. Which of the following compounds is a saturated hydrocarbon?

[RRB Group D — 14 Dec 2025, Shift 3]

(A) Benzene

(B) Propene

(D) Cyclohexane

Answer: (D) Cyclohexane

Explanation: Cyclohexane is a saturated cyclic hydrocarbon whose ring carbons are connected exclusively by single bonds. Propene and propyne have multiple carbon bonds, while benzene has an aromatic delocalised system. Cyclic saturation does not require the open-chain alkane formula.

251. Which of the following is an organic compound?

[RRB Group D — 11 Dec 2025, Shift 3]

(A) NaCl

(B) C₂H₆

(D) Na₂CO₃

Answer: (B) C₂H₆

Explanation: Ethane, C₂H₆, is a covalently bonded hydrocarbon and a member of the alkane series. Sodium chloride is inorganic, while calcium and sodium carbonates are conventionally classified as inorganic carbon compounds. Carbon content alone does not establish organic classification.

250. Which of the following has a branched-chain hydrocarbon?

[RRB Group D — 10 Dec 2025, Shift 1]

(A) Isobutane

(B) Butane

(D) Ethane

Answer: (A) Isobutane

Explanation: Isobutane is 2-methylpropane and has a side branch in its carbon skeleton. The other three choices are straight-chain alkanes. Isobutane and normal butane are structural isomers, illustrating how hydrocarbons can share a molecular formula but have different structures.

249. Which property of carbon permits one carbon atom to bond with other carbon atoms?

[RRB Group D — 09 Dec 2025, Shift 2]

(A) Valency

(B) Polymerisation

(D) Isomerisation

Answer: (C) Catenation

Explanation: Catenation allows carbon atoms to form chains, branched structures and rings by bonding to other carbon atoms. The comparatively strong carbon–carbon covalent bond gives these structures stability. Polymerisation is a chemical process, whereas catenation is an underlying bonding capability.

248. An organic compound always contains which of the following?

[RRB Group D — 09 Dec 2025, Shift 1]

(A) Silicon and phosphorus

(B) Halogens and noble gases

(D) At least one carbon atom

Answer: (D) At least one carbon atom

Explanation: Organic compounds contain carbon, although not every carbon compound is classed as organic. Many organic molecules also contain hydrogen, oxygen, nitrogen or halogens, but these additional elements are not universal requirements. Carbon-based bonding provides the essential chemical framework.

247. What type of bonding exists in most organic compounds?

[RRB Group D — 08 Dec 2025, Shift 1]

(A) Coordinate

(B) Covalent

(D) Metallic

Answer: (B) Covalent

Explanation: Covalent bonding involves the sharing of electron pairs between atoms. It predominates in the carbon skeletons of organic molecules because carbon bonds readily with nonmetals. This is why many molecular organic compounds lack the mobile charged particles needed for electrical conduction.

246. What is the IUPAC name of an organic compound having two carbon atoms and a hydroxyl (–OH) group?

[RRB Group D — 05 Dec 2025, Shift 3]

(A) Methanal

(B) Ethanol

(D) Ethanoic acid

Answer: (B) Ethanol

Explanation: The prefix eth- identifies two carbon atoms, while the suffix -ol identifies an alcohol containing a hydroxyl functional group. The compound is ethanol, C₂H₅OH. Methanal is an aldehyde, propanone a ketone, and ethanoic acid a carboxylic acid.

245. Detergents can work in which of the following?

[RRB Group D — 05 Dec 2025, Shift 3]

(A) Only distilled water

(B) Only hot water

(D) Both hard and soft water

Answer: (D) Both hard and soft water

Explanation: Many synthetic detergents remain effective in hard water because their calcium and magnesium salts generally do not produce the same insoluble scum as ordinary soaps. This makes detergents useful for washing where dissolved mineral ions are abundant.

244. Which of the following products is formed on complete combustion of hydrocarbons?

[RRB Group D — 05 Dec 2025, Shift 2]

(A) CO and water

(B) CO₂ and water

(D) Methane and oxygen

Answer: (B) CO₂ and water

Explanation: Hydrocarbons contain carbon and hydrogen. When oxygen is sufficient, carbon is fully oxidised to carbon dioxide and hydrogen to water. Carbon monoxide may arise under oxygen-limited combustion and should not be confused with the normal products of complete burning.

243. Which compound is classified as a saturated hydrocarbon?

[RRB Group D — 03 Dec 2025, Shift 3]

(A) Benzene

(B) Ethane

(D) Ethene

Answer: (B) Ethane

Explanation: Ethane is an alkane with only single covalent bonds and the molecular formula C₂H₆. Ethene contains a double bond, ethyne a triple bond, and benzene is aromatic. Thus ethane represents a fully saturated open-chain hydrocarbon.

242. Which structural formula represents the branched-chain compound neopentane?

[RRB Group D — 03 Dec 2025, Shift 2]

(A) CH₃–CH(CH₃)–CH₂–CH₂–CH₃

(B) CH₃–CH(CH₃)–CH₃

(D) C(CH₃)₄

Answer: (D) C(CH₃)₄

Explanation: Neopentane is 2,2-dimethylpropane, one of the three structural isomers of pentane. A central carbon is bonded to four methyl groups, yielding the condensed formula C(CH₃)₄. Its compact branching gives distinctive physical properties.

241. When a hydrocarbon is burnt in excess air, the final products are:

[RRB Group D — 01 Dec 2025, Shift 2]

(A) Carbon dioxide and hydrogen

(B) Carbon monoxide and water

(D) Carbon dioxide and water

Answer: (D) Carbon dioxide and water

Explanation: Excess air provides enough oxygen for complete combustion. The carbon atoms in a hydrocarbon form carbon dioxide and the hydrogen atoms form water. This oxidation releases useful energy and explains why hydrocarbons serve as widely used fuels.

240. Which of the following is NOT considered an organic compound?

[RRB Group D — 01 Dec 2025, Shift 1]

(A) Sodium carbonate (Na₂CO₃)

(B) Acetic acid (CH₃COOH)

(D) Ethanol (C₂H₅OH)

Answer: (A) Sodium carbonate (Na₂CO₃)

Explanation: Sodium carbonate is classified as an inorganic salt despite containing carbon. Acetic acid, methane and ethanol are organic compounds with typical carbon frameworks and carbon–hydrogen bonding. Carbonates, carbon dioxide and certain other carbon compounds are traditionally treated as inorganic.

239. Which of the following has a straight-chain hydrocarbon?

[RRB Group D — 27 Nov 2025, Shift 3]

(A) 3-Methylpentane

(B) 2-Methylpropane

(D) Butane

Answer: (D) Butane

Explanation: Butane has an unbranched chain of four carbon atoms. The other options describe molecules containing side branches. Structural differences can exist even between compounds that share a molecular formula, as illustrated by normal butane and isobutane.

238. Which of these organic compounds is saturated?

[RRB Group D — 27 Nov 2025, Shift 3]

(A) Bromopropane

(B) Propyne

(D) Propene

Answer: (A) Bromopropane

Explanation: Bromopropane has only single carbon–carbon bonds even though one hydrogen atom is substituted by bromine. Propyne has a triple bond, and propene or bromopropene contains a double bond. Saturation concerns multiple bonds in the carbon skeleton.

237. Match each polymer to its monomer unit:
(i) Glyptal,
(ii) Bakelite,
(iii) Nylon-2-nylon-6,
(iv) Buna-N.

(A) Glycine + aminocaproic acid,
(B) Phenol + formaldehyde,
(C) Butadiene + acrylonitrile,
(D) Ethylene glycol + phthalic acid.

[RPSC Senior Teacher Grade II (Science) — 09 Sep 2025]

(A) (i)-D, (ii)-B, (iii)-A, (iv)-C

(B) (i)-D, (ii)-B, (iii)-C, (iv)-A

(D) (i)-A, (ii)-B, (iii)-C, (iv)-D

Answer: (A) (i)-D, (ii)-B, (iii)-A, (iv)-C

Explanation: Glyptal is derived from ethylene glycol and phthalic acid; Bakelite from phenol and formaldehyde. Nylon-2-nylon-6 uses glycine and aminocaproic acid, and Buna-N combines butadiene with acrylonitrile. Identifying monomers reveals polymer structure and classification.

236. What is the full form of PETN, an explosive referred to in tunnelling applications?

[RRB JE Civil CBT-2 — 22 Apr 2025]

(A) Pentane Energy Nitrate

(B) Polyethylene Nitrogen Trinitrate

(D) Pentaerythritol Tetranitrate

Answer: (D) Pentaerythritol Tetranitrate

Explanation: PETN stands for pentaerythritol tetranitrate. It is an energetic nitrate ester, conventionally discussed in chemistry and engineering examinations under explosive materials. Its name identifies a specific compound rather than a generic category of industrial blasting substances.

235. The most powerful explosive used in blasting among the following is:

[SSC JE Civil — 05 Dec 2025, Shift 1]

(A) Blasting powder

(B) Dynamite

(D) Cordite

Answer: (C) Gun cotton

Explanation: Gun cotton is a form of nitrated cellulose and is grouped among energetic materials. The question compares named substances appearing in engineering examinations; their practical properties depend on composition and conditions. This is a classification question, not an instruction for use.

234. Which of the following is an example of a synthetic polymer used in industry?

[RRB NTPC UG CBT-I — 20 Aug 2025, Shift 3]

(A) Starch

(B) Nylon-6,6

(D) Rubber

Answer: (B) Nylon-6,6

Explanation: Nylon-6,6 is a synthetic polyamide made by condensation polymerisation of hexamethylenediamine and adipic acid. Its strong amide-linked chains provide toughness and abrasion resistance. Starch, cellulose and natural rubber are naturally occurring macromolecules rather than this industrially manufactured polyamide.

233. Which resilient polymer is used in industrial brushes and toothbrush bristles?

[RRB NTPC UG CBT-I — 08 Aug 2025, Shift 2]

(A) Neoprene

(B) Terylene

(D) Nylon-6,6

Answer: (D) Nylon-6,6

Explanation: Nylon-6,6 is a strong, flexible synthetic polyamide that retains its shape under repeated bending, making it useful for bristles. Neoprene is an elastomer, Terylene is a polyester fibre, and Teflon is valued primarily for chemical resistance and non-stick applications.

232. DNA is a polymer of deoxyribonucleotides. Which structural feature does this describe?

[RRB NTPC Graduate CBT-I — 16 Jun 2025, Shift 1]

(A) Sugar-phosphate backbone with nitrogenous bases

(B) Nucleotides linked by parallel hydrogen bonds

(D) A necessarily circular self-replicating structure

Answer: (A) Sugar-phosphate backbone with nitrogenous bases

Explanation: DNA consists of nucleotide units connected through phosphodiester links forming a repeating sugar-phosphate backbone. Each sugar carries a nitrogenous base. Hydrogen bonds hold complementary strands together, but they are not the covalent linkages that form an individual DNA polymer chain.

231. Amylopectin consists mainly of glucose units joined along its chains by which bonds?

[RRB NTPC UG CBT-I — 11 Aug 2025, Shift 1]

(A) α-1,4 glycosidic bonds

(B) β-1,4 glycosidic bonds

(D) α-1,2 glycosidic bonds

Answer: (A) α-1,4 glycosidic bonds

Explanation: Amylopectin is the branched component of starch. Its glucose residues are linked mainly by alpha-1,4 glycosidic bonds along the chains, while alpha-1,6 bonds occur at branch points. These linkage types help distinguish amylopectin from cellulose and other polysaccharides.

230. Biogas plants are most commonly used in which sector in rural India?

[RRB NTPC UG CBT-I — 02 Sep 2025, Shift 2]

(A) Industrial use

(B) Household cooking and lighting

(D) Iron smelting

Answer: (B) Household cooking and lighting

Explanation: Village biogas units digest dung and biodegradable waste without oxygen. The resulting methane-rich gas can supply households with fuel for cooking and lighting. The residue may be used as manure, making the system helpful for household energy needs and waste treatment.

229. What fuel combination was announced for ISRO’s Next Generation Launch Vehicle engine?

[RRB NTPC UG CBT-I — 18 Aug 2025, Shift 3]

(A) Liquid oxygen–kerosene hybrid

(B) Hydrogen-fuelled engine

(D) Liquid oxygen–methane engine

Answer: (D) Liquid oxygen–methane engine

Explanation: The LOX–methane concept combines liquid oxygen as oxidiser with methane as the hydrocarbon fuel. Methane is considered promising for reusable propulsion because it can burn relatively cleanly compared with heavier hydrocarbon fuels. It is therefore a relevant advanced application of organic fuel chemistry.

228. How many additional million tonnes of FCI rice were allocated for ethanol production in May 2025?

[RRB NTPC UG CBT-I — 20 Aug 2025, Shift 2]

(A) 2.1 million tonnes

(B) 2.8 million tonnes

(D) 2.4 million tonnes

Answer: (B) 2.8 million tonnes

Explanation: The reported additional allocation was 2.8 million tonnes. Starch-rich rice can be converted into fermentable sugars, which yeast converts into ethanol. Fuel ethanol is blended with petrol to substitute part of the fossil-derived liquid fuel and support domestic biofuel production.

227. Which initiative supports compressed biogas plants supplying automotive and industrial fuels to oil marketing companies?

[RRB NTPC UG CBT-I — 13 Aug 2025, Shift 1]

(A) Biogas Programme

(B) Waste to Energy Programme

(D) Sustainable Alternative Towards Affordable Transportation

Answer: (D) Sustainable Alternative Towards Affordable Transportation

Explanation: The SATAT initiative promotes compressed biogas from organic wastes as a transport and industrial fuel. Biogas is upgraded to increase its methane content and then compressed for distribution. This can simultaneously reduce organic waste and displace a portion of fossil-derived natural gas.

226. Which engine under development for ISRO’s LVM3 uses a kerosene-based fuel system?

[RRB NTPC UG CBT-I — 14 Aug 2025, Shift 2]

(A) Electric jet engine

(B) Turbo plasma engine

(D) Liquid booster

Answer: (C) Semicryogenic engine

Explanation: A semicryogenic rocket engine can use liquid oxygen with refined kerosene, a mixture of petroleum hydrocarbons, as its fuel. Compared with liquid-hydrogen systems, kerosene is denser and can simplify some storage needs. The question links hydrocarbon fuels to propulsion technology.

225. What is the defining characteristic of an unsaturated carbon compound?

[RRB Group D — 28 Nov 2025, Shift 1]

(A) Only single carbon-carbon bonds

(B) An obligatory oxygen-containing group

(D) At least one carbon-carbon double or triple bond

Answer: (D) At least one carbon-carbon double or triple bond

Explanation: Unsaturation is defined by a carbon-carbon double or triple bond, not by the shape of the carbon skeleton or the presence of oxygen. Alkenes and alkynes are common examples. Such multiple bonds generally favour addition reactions unavailable to simple alkanes.

224. Which of the following compounds is unsaturated?

[RRB Group D — 04 Dec 2025, Shift 1]

(A) Butane

(B) Propane

(D) Methane

Answer: (C) Propene

Explanation: Propene is an alkene with formula C₃H₆ and one carbon-carbon double bond. Butane, propane and methane are saturated alkanes containing only single bonds. The distinguishing double bond makes propene eligible for addition and polymerisation reactions.

223. Which carbon properties together explain the huge diversity of organic compounds?

[RRB Group D — 27 Nov 2025, Shift 2]

(A) Both tetravalency and catenation

(B) Only catenation

(D) Solubility

Answer: (A) Both tetravalency and catenation

Explanation: Tetravalency allows carbon atoms to form four covalent bonds, while catenation permits stable bonding with other carbon atoms. Together they create chains, branches and rings. Double and triple bonding further multiply structural possibilities and the diversity of organic compounds.

222. Which of the following are building blocks of proteins?

[SSC MTS — 14 Nov 2024, Shift 1]

(A) Amino acids

(B) Bases

(D) Acids

Answer: (A) Amino acids

Explanation: Proteins are natural polymers made from amino acids connected by peptide bonds. Their sequences determine folding and biological activity. Amino acids commonly contain both an amino group and a carboxyl group, making them important organic compounds in biochemistry.

221. What is denatured alcohol?

[SSC MTS — 05 Nov 2024, Shift 1]

(A) Pure ethanol

(B) Ethanol mixed with a little methanol

(D) Propanol

Answer: (B) Ethanol mixed with a little methanol

Explanation: Denatured alcohol is ethanol rendered unsuitable for drinking by adding substances such as methanol or bittering agents. It is used for industrial and cleaning purposes. Its exact formulation varies with local regulations and intended industrial application.

220. What is the chemical name of the compound responsible for the cooling sensation in mint leaves?

[SSC MTS — 04 Nov 2024, Shift 3]

(A) Ethanol

(B) Menthol

(D) Capsaicin

Answer: (B) Menthol

Explanation: Menthol is an organic compound found in mint oils. It activates cold-sensitive receptors, creating a cooling sensation without necessarily reducing temperature. Caffeine is a stimulant, capsaicin produces a hot sensation, and ethanol is a simple alcohol.

219. What is the primary acid found in citrus fruits such as oranges and lemons?

[SSC MTS — 22 Oct 2024, Shift 2]

(A) Lactic acid

(B) Tartaric acid

(D) Acetic acid

Answer: (C) Citric acid

Explanation: Citric acid is a naturally occurring organic tricarboxylic acid responsible for much of the tart flavour of citrus fruits. It is used in foods and beverages as an acidulant. It differs from ascorbic acid, which is vitamin C.

218. Which organism is used in the bread and alcohol industries?

[SSC MTS — 22 Oct 2024, Shift 1]

(A) Clostridium

(B) Nitrobacter

(D) Penicillium

Answer: (C) Yeast

Explanation: Yeast ferments sugars anaerobically to generate ethanol and carbon dioxide. Carbon dioxide makes bread dough rise, while ethanol is the desired product in alcoholic fermentation. This biological process provides an important industrial route to a familiar organic alcohol.

217. Which gas is released when vinegar and baking soda are combined, inflating a balloon?

[SSC MTS — 08 Oct 2024, Shift 2]

(A) Carbon dioxide

(B) Hydrogen

(D) Nitrogen

Answer: (A) Carbon dioxide

Explanation: Acetic acid in vinegar reacts with sodium hydrogen carbonate in baking soda to release carbon dioxide, alongside water and sodium acetate. The gas expands and inflates the balloon. This demonstrates a gas-evolving acid–hydrogen carbonate reaction.

216. Which reaction forms glucose pentaacetate when glucose reacts with acetic anhydride?

[SSC CHSL — 05 Jul 2024, Shift 3]

(A) Reduction

(B) Addition of ketone

(D) Acetylation of glucose

Answer: (D) Acetylation of glucose

Explanation: Glucose contains five hydroxyl groups capable of being acetylated. Reaction with acetic anhydride gives glucose pentaacetate. This is a modification of hydroxyl groups rather than reduction or oxidation and illustrates an important transformation in carbohydrate chemistry.

215. What does RDX stand for, according to the given options?

[UP Police Constable Re-exam — 30 Aug 2024, Shift 2]

(A) Research Department Expansion

(B) Research Department Explosive

(D) Raw Detonation Explosive

Answer: (B) Research Department Explosive

Explanation: Research Department Explosive is a commonly given expansion of RDX in general-knowledge examinations. The substance is also known as cyclonite or hexogen. Such naming questions concern identification of an energetic compound, not its synthesis or use.

214. What is the full form of TNT?

[OSSSC Forest Guard — 03 May 2024, Shift 2]

(A) Trinitrotoxin

(B) Trinitrotetra

(D) Trinitrotoluene

Answer: (D) Trinitrotoluene

Explanation: TNT is the conventional abbreviation for trinitrotoluene, an aromatic organic compound known as an explosive. The name points to a toluene-derived structure bearing three nitro groups. The question asks only for recognition of its chemical name.

213. What is the molecular formula of the first member of the alkene series?

[RRB JE CBT-I — 16 Dec 2024, Shift 3]

(A) C₅H₁₀

(B) C₂H₄

(D) C₄H₆

Answer: (B) C₂H₄

Explanation: Ethene, C₂H₄, is the simplest stable alkene and contains a carbon-carbon double bond. Open-chain monoalkenes generally follow CnH₂n. At least two carbon atoms are needed to form a carbon-carbon double bond, so methane has no corresponding one-carbon alkene.

212. In which Madhya Pradesh district is a polymer-manufacturing factory located?

[MPPSC Assistant Professor (Geography Paper II) — 04 Aug 2024]

(A) Betul

(B) Chhindwara

(D) Neemuch

Answer: (B) Chhindwara

Explanation: Chhindwara is the district identified in the examination as hosting a polymer manufacturing facility. Polymers are large molecules made from repeating structural units and underpin products such as plastics, fibres and elastomers. This question tests industrial geography related to polymer production.

211. Which of the following is not a natural fibre?

[SSC CGL 2022 Tier-II JSO paper — held 04 Mar 2023]

(A) Linen

(B) Cotton

(D) Jute

Answer: (C) Rayon

Explanation: Rayon is a man-made regenerated cellulose fibre, produced by processing natural cellulose chemically. Linen, cotton and jute are obtained directly from plant sources. Rayon is often described as semi-synthetic because its raw material is a natural polymer.

210. Trinitrotoluene is used for which purpose?

[MP Patwari Group 2 Sub Group 4 — 24 Apr 2023, Shift 2]

(A) As an explosive

(B) As an abrasive

(D) To melt metals

Answer: (A) As an explosive

Explanation: Trinitrotoluene, abbreviated TNT, is an organic nitro compound used as an explosive material. It is not ordinarily classified as an abrasive, a metal-bonding agent or a metal-melting substance. The item tests recognition of a compound’s general use.

209. Which compound–melting point pair is correct?
I. Acetic acid—290 K.
II. Ethanol—156 K.

[SSC CGL Tier-I — 27 Jul 2023, Shift 3]

(A) Only I

(B) Both I and II

(D) Only II

Answer: (B) Both I and II

Explanation: Pure acetic acid freezes near 16.6°C, equivalent to about 290 K, whereas ethanol melts around minus 114°C, roughly 159 K. Many school references round ethanol’s melting point close to 156 K. Both exam-specified pairs were treated as correct.

208. Which class of organic compounds contains the –OH functional group?

[SSC CGL Tier-II — 03 Mar 2023]

(A) Alcohol

(B) Ethane

(D) Aldehyde

Answer: (A) Alcohol

Explanation: An alcohol has a hydroxyl group, –OH, bonded to a saturated carbon atom. Ethane is an alkane without oxygen; ketones contain an internal carbonyl group and aldehydes have a terminal carbonyl group. The functional group governs typical chemical reactions.

207. What is the approximate proportion of methane in cow-dung biogas?

[WBCS Mains (Science) — 2023]

(A) 30%

(B) 40%

(D) 60%

Answer: (D) 60%

Explanation: Cow-dung biogas commonly contains about 55–65 percent methane, with most of the remainder being carbon dioxide and traces of other gases. Methane provides the main combustible component, explaining why the gas is useful for cooking and rural energy generation.

206. Which of these tranquilising medicines is a barbiturate?

[NEET Chemistry — 2023]

(A) Meprobamate

(B) Valium

(D) Chlordiazepoxide

Answer: (C) Veronal

Explanation: Veronal is a historical name for barbital, one of the earliest barbiturate sedatives. Valium and chlordiazepoxide are benzodiazepines, while meprobamate is a carbamate anxiolytic. Recognising the underlying heterocyclic or functional-group frameworks distinguishes these related pharmaceutical categories.

205. Complete the anaerobic respiration reaction: Glucose → ______ + carbon dioxide + energy.

[RRB Group D — 11 Oct 2022, Shift 1]

(A) Pyruvate

(B) Water

(D) Ethanol

Answer: (D) Ethanol

Explanation: In alcoholic fermentation, yeast enzymes convert glucose through intermediate steps into ethanol and carbon dioxide, releasing some usable energy. Lactic acid instead arises in a different anaerobic pathway. Fermentation is an important biological production route for ethanol.

204. Which of the following compounds contains only one carbon–carbon single bond?

[RRB Group D — 30 Sep 2022, Shift 2]

(A) Ethane

(B) Propane

(D) Methane

Answer: (A) Ethane

Explanation: Ethane contains two carbon atoms connected by exactly one carbon–carbon single bond. Propane has two such bonds, butane has three, and methane has only one carbon atom and therefore no carbon–carbon bond at all.

203. The general formula CnH2n−2 represents:

[RRB Group D — 27 Sep 2022, Shift 2]

(A) Alkyne

(B) Alkene

(D) Acyclic compound

Answer: (A) Alkyne

Explanation: Open-chain alkynes containing one triple bond commonly follow CnH2n−2. Alkenes with one double bond follow CnH2n, while alkanes follow CnH2n+2. These formulas express differences in hydrogen saturation for comparable carbon chain lengths.

202. Why do typical carbon compounds not conduct electricity in the molten state?

[RRB Group D — 27 Sep 2022, Shift 2]

(A) Their bonding generally does not form mobile ions

(B) They are ionic

(D) Their bonds form mobile ions

Answer: (A) Their bonding generally does not form mobile ions

Explanation: Most simple molecular carbon compounds are covalently bonded and do not generate freely moving ions on melting. Electrical conduction requires mobile charged particles. Graphite and certain other carbon-containing substances are exceptions, so the question refers to typical molecular organic compounds.

201. Carbon compounds linked by only single carbon–carbon bonds are known as:

[RRB Group D — 27 Sep 2022, Shift 1]

(A) Both saturated and unsaturated

(B) Neither saturated nor unsaturated

(D) Unsaturated compounds

Answer: (C) Saturated compounds

Explanation: Saturated carbon compounds contain only single carbon–carbon bonds and have no carbon–carbon double or triple bonds. By contrast, unsaturated hydrocarbons contain multiple bonds and commonly undergo addition reactions. Alkanes are typical examples of saturated hydrocarbons.

200. Which carbon compound is a major component of both biogas and compressed natural gas?

[RRB Group D — 26 Sep 2022, Shift 1]

(A) Methane

(B) Butane

(D) Propane

Answer: (A) Methane

Explanation: Methane is the principal combustible constituent of natural gas and is also a major component of biogas. It has the formula CH₄ and is the simplest alkane. Methane-rich fuels release heat on combustion with adequate oxygen.

199. Why are most carbon compounds poor conductors of electricity?

[RRB Group D — 26 Sep 2022, Shift 1]

(A) They generally do not form mobile ions

(B) They are all solids

(D) They have very high melting points

Answer: (A) They generally do not form mobile ions

Explanation: Ordinary molecular carbon compounds are largely covalent. Their electrons are localised within molecular bonds and they usually lack mobile ions or electrons. This is why many organic liquids and solids conduct electricity poorly, apart from specialised conducting materials.

198. What type of bonding is present in most carbon compounds?

[RRB Group D — 22 Sep 2022, Shift 3]

(A) Metallic bonding

(B) Hydrogen bonding

(D) Covalent bonding

Answer: (D) Covalent bonding

Explanation: Carbon commonly shares valence electrons with other atoms to complete stable outer shells. This sharing produces covalent bonds, including single, double and triple bonds. Organic molecular structures depend mainly on such shared electron pairs rather than metal-like conduction or ionic lattices.

197. Which carbon compound is formed by fermentation of molasses?

[RRB Group D — 20 Sep 2022, Shift 3]

(A) Propanol

(B) Ethane

(D) Ethanol

Answer: (D) Ethanol

Explanation: Molasses contains sugars that yeast can ferment into ethanol and carbon dioxide under suitable conditions. Ethanol is a two-carbon alcohol useful in fuels and industry. Ethane and methane are hydrocarbons, whereas propanol is not the usual major product.

196. Which of the following is the general formula of an alkene?

[RRB Group D — 19 Sep 2022, Shift 2]

(A) CnH2n+4

(B) CnH2n−2

(D) CnH2n

Answer: (D) CnH2n

Explanation: An acyclic alkene with one carbon–carbon double bond ordinarily has the formula CnH2n. The related saturated alkane contains two additional hydrogen atoms. Alkynes containing one triple bond instead commonly fit the formula CnH2n−2.

195. Which statement is correct for saturated carbon compounds?

[RRB Group D — 19 Sep 2022, Shift 1]

(A) They have carbon–carbon double bonds only

(B) They have carbon–carbon single bonds only

(D) They have both double and triple bonds

Answer: (B) They have carbon–carbon single bonds only

Explanation: A saturated carbon skeleton contains only single bonds between its carbon atoms. This contrasts with alkenes and alkynes, which have double or triple bonds. Saturated alkanes are less prone to typical addition reactions than unsaturated hydrocarbons.

194. Carbon exhibits catenation because of:

[RRB Group D — 17 Sep 2022, Shift 2]

(A) Small size and strong carbon–carbon bonds

(B) Large size and strong carbon–carbon bonds

(D) Large size and weak carbon–carbon bonds

Answer: (A) Small size and strong carbon–carbon bonds

Explanation: Carbon’s small atomic size allows effective overlap of orbitals and strong carbon–carbon covalent bonds. Consequently, carbon atoms form stable linked chains and rings. Catenation, combined with tetravalency, accounts for much of the remarkable structural diversity of organic substances.

193. What is the major product when ethanol reacts with acidified potassium dichromate?

[RRB Group D — 15 Sep 2022, Shift 3]

(A) Ethanal

(B) Ethene

(D) Ethanoic acid

Answer: (D) Ethanoic acid

Explanation: Acidified potassium dichromate is a strong oxidising agent. It converts ethanol, a primary alcohol, to ethanal and then to ethanoic acid under sufficiently oxidising conditions. The final product contains the carboxyl –COOH functional group.

192. Which bond is generally not found in typical carbon compounds?

[RRB Group D — 14 Sep 2022, Shift 1]

(A) Single bond

(B) Double bond

(D) Triple bond

Answer: (C) Ionic bond

Explanation: Typical organic carbon frameworks use covalent single, double and triple bonds formed through electron sharing. An ionic carbon–carbon framework is not characteristic of ordinary hydrocarbons. Some organic salts do contain ions, so the question refers to the usual bonding pattern.

191. Which of the following is a two-carbon molecule?

[RRB Group D — 13 Sep 2022, Shift 3]

(A) Lactic acid

(B) Ethanol

(D) Glucose

Answer: (B) Ethanol

Explanation: Ethanol contains two carbon atoms and has the molecular formula C₂H₆O, often written C₂H₅OH. Lactic and pyruvic acids each contain three carbon atoms, while glucose contains six. Counting carbons helps identify organic compounds from their formulas.

190. Why do many molecular organic carbon compounds have lower melting points than ionic compounds?

[RRB Group D — 13 Sep 2022, Shift 1]

(A) Presence of ionic bonds

(B) Presence of covalent bonds alone

(D) Relatively weak intermolecular attractions

Answer: (D) Relatively weak intermolecular attractions

Explanation: Although covalent bonds within an organic molecule may be strong, the forces between separate molecules are often comparatively weak. Melting many such substances therefore requires less energy than disrupting the strong electrostatic attraction in a typical ionic crystal.

189. Hydrocarbons with a double bond between two carbon atoms are called:

[RRB Group D — 09 Sep 2022, Shift 2]

(A) Inorganic compounds

(B) Natural compounds

(D) Unsaturated compounds

Answer: (D) Unsaturated compounds

Explanation: A carbon–carbon double bond indicates unsaturation because fewer hydrogen atoms are present than in the corresponding saturated alkane. Alkenes are the main open-chain class featuring such bonds. These molecules often undergo addition across the double bond.

188. Which of the following members of the alkane series has the highest melting point?

[RRB Group D — 08 Sep 2022, Shift 3]

(A) C₄H₁₀

(B) C₂H₆

(D) CH₄

Answer: (A) C₄H₁₀

Explanation: Among the listed small alkanes, butane has the highest melting point. Molecular packing and London dispersion interactions affect alkane melting behaviour. The general trend with increasing carbon number is useful, although melting points are not perfectly monotonic throughout homologous series.

187. Which gas evolves during complete burning of natural gas (CH₄)?

[RRB Group D — 06 Sep 2022, Shift 3]

(A) NH₃

(B) CO₂

(D) H₂

Answer: (B) CO₂

Explanation: Methane reacts with sufficient oxygen to produce carbon dioxide and water while releasing heat. The balanced combustion equation is CH₄ + 2O₂ → CO₂ + 2H₂O. Natural gas is a major domestic and industrial hydrocarbon fuel.

186. Which of these statements is correct?

[RRB Group D — 06 Sep 2022, Shift 2]

(A) Ethanol has three carbon atoms

(B) Acetic acid has two carbon atoms

(D) Chloroform has three carbon atoms

Answer: (B) Acetic acid has two carbon atoms

Explanation: Acetic acid has the structure CH₃COOH and therefore contains two carbon atoms. Ethanol also has two, methane has one, and chloroform has one. Comparing formulas instead of names helps avoid common errors in carbon counting.

185. Statement I: Most carbon compounds are good conductors of electricity.
Statement II: Intermolecular forces in many molecular carbon compounds are not very strong.

Choose the correct answer.

[RRB Group D — 02 Sep 2022, Shift 1]

(A) II correct; I incorrect

(B) I correct; II incorrect

(D) Both correct

Answer: (A) II correct; I incorrect

Explanation: Most common molecular organic compounds lack mobile charge carriers, so statement I is incorrect. Their intermolecular forces are frequently weaker than ionic-lattice forces, making statement II broadly correct. Some carbon allotropes and conducting polymers are exceptions.

184. Which element shows catenation property similar to carbon?

[RRB Group D — 01 Sep 2022, Shift 2]

(A) Ne

(B) Si

(D) K

Answer: (B) Si

Explanation: Silicon, like carbon, is a group 14 element with four valence electrons. It can form silicon–silicon covalent bonds and linked structures, though its catenation tendency is generally less extensive than that of carbon. Neon and potassium are unsuitable examples here.

183. The catenation property shown by carbon refers to:

[RRB Group D — 01 Sep 2022, Shift 1]

(A) Self-combination to form long atomic chains

(B) Occurrence as different allotropes

(D) Giving combustibility to all compounds

Answer: (A) Self-combination to form long atomic chains

Explanation: Catenation is an element’s ability to bond with atoms of its own kind. Carbon forms long chains, branched frameworks and rings because carbon–carbon bonds are strong and stable. This is distinct from allotropy, which describes different structural forms of an element.

182. Which chemicals are used in traditional gunpowder for fireworks?

[SSC CPO — 09 Nov 2022, Shift 2]

(A) Silver nitrate and charcoal

(B) Silver nitrate and sulphur

(D) Potassium nitrate, sulphur and charcoal

Answer: (D) Potassium nitrate, sulphur and charcoal

Explanation: The historical term black powder denotes a mixture involving potassium nitrate, sulphur and charcoal. In examinations it is identified by its constituent names and classified as an early explosive material. The question concerns factual recognition, not preparation.

181. Which of the following is not a biofuel?

[WBCS Mains 2021 — held May 2022, Paper IV]

(A) Vegetable oil

(B) Green diesel

(D) Gasoline

Answer: (D) Gasoline

Explanation: Vegetable oils, renewable diesel and biogas can be obtained from biomass or other renewable biological feedstocks. Conventional gasoline is primarily a petroleum-refining product containing a mixture of hydrocarbons. Therefore it is not ordinarily categorised as a biofuel.

180. Which greenhouse gas is produced when fossil fuels burn?

[WBCS Mains 2021 — held May 2022, Paper IV]

(A) Methane

(B) Carbon monoxide

(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

(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

(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

(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

(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

(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

(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

(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

(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

(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.

170. Which feedstocks qualify under India’s National Policy on Biofuels:
1 Cassava,
2 damaged wheat,
3 groundnut,
4 horse gram,
5 rotten potatoes,
6 sugar beet?

[UPSC CSE Prelims — 2020]

(A) 1, 2, 5 and 6 only

(B) 1, 3, 4 and 6 only

(D) All six

Answer: (A) 1, 2, 5 and 6 only

Explanation: The policy recognises a variety of sugar- and starch-rich materials for ethanol production, including cassava, damaged wheat, rotten potatoes and sugar beet. Oilseeds and pulse crops are not automatically included within this specific listed category. The correct combination is 1, 2, 5 and 6.

169. Which order did the given CGPSC question identify for contributions to the greenhouse effect?

[CGPSC Civil Service Prelims — 2020]

(A) CO₂ > CH₄ > CFCs > N₂O

(B) CH₄ > CO₂ > CFCs > N₂O

(D) CO₂ > CH₄ > N₂O > CFCs

Answer: (D) CO₂ > CH₄ > N₂O > CFCs

Explanation: The examination key selected the listed ordering with carbon dioxide followed by methane, nitrous oxide and CFCs. Modern scientific comparisons depend on whether one measures atmospheric concentration, radiative forcing or warming potential; these quantities must not be confused. The item reproduces the historical answer key.

168. Which of these cleaning agents is a cationic detergent?

[NEET Phase 1 Chemistry — 2020]

(A) Sodium stearate

(B) Cetyltrimethylammonium bromide

(D) Sodium lauryl sulphate

Answer: (B) Cetyltrimethylammonium bromide

Explanation: Cetyltrimethylammonium bromide is a quaternary ammonium salt whose surfactant head carries a positive charge. Sodium lauryl sulphate and sodium dodecylbenzene sulphonate have anionic heads. Sodium stearate is a conventional soap, not the cationic detergent specified in the paper.

167. Which one of the following is not a natural polymer?

[RPSC Senior Teacher Science — 04 Jul 2019]

(A) Teflon

(B) Starch

(D) Cellulose

Answer: (A) Teflon

Explanation: Teflon, or polytetrafluoroethylene, is a synthetic polymer. Starch and cellulose are naturally occurring polysaccharides, while proteins are natural polymers of amino acids. Distinguishing naturally occurring macromolecules from manufactured polymers is central to basic polymer chemistry.

166. What are the monomer units of Glyptal?

[RPSC Senior Teacher Science — 04 Jul 2019]

(A) Urea and formaldehyde

(B) Phenol and formaldehyde

(D) Ethylene glycol and terephthalic acid

Answer: (C) Ethylene glycol and phthalic acid

Explanation: Glyptal is a polyester resin made from ethylene glycol and phthalic acid through condensation polymerisation. Terephthalic acid with ethylene glycol instead forms PET-type polyester. Phenol and formaldehyde yield a different thermosetting polymer, Bakelite.

165. Which one of the following is a non-reducing sugar?

[RPSC Senior Teacher Science — 04 Jul 2019]

(A) Glucose

(B) Maltose

(D) Sucrose

Answer: (D) Sucrose

Explanation: Sucrose lacks a free anomeric hemiacetal or hemiketal because the anomeric centres of glucose and fructose are joined in its glycosidic bond. It therefore does not behave as a typical reducing sugar. Glucose, lactose and maltose can act as reducing sugars.

164. Which substances form the traditional composition of gunpowder?

[Kerala SET Paper 1 — Jul 2019]

(A) Aluminium nitrate, charcoal and sulphur

(B) Potassium nitrate, charcoal and sulphur

(D) Charcoal and TNT

Answer: (B) Potassium nitrate, charcoal and sulphur

Explanation: Traditional black powder is identified in general chemistry by potassium nitrate, charcoal and sulphur as constituent substances. It is a historical explosive mixture. The test is about naming its components, not about proportions, mixing or practical application.

163. Which of the following is not a named explosive in the given tunnelling-material list?

[MPSC Assistant Engineer Civil Mains — 2019, Paper 2]

(A) PENT

(B) RDX

(D) NTT

Answer: (D) NTT

Explanation: PETN, RDX and TNT are established names or abbreviations encountered in classifications of explosive materials. NTT is not a recognised standard substance in the question’s list. The item requires identifying terminology rather than predicting behaviour or handling characteristics.

162. Biogas consists primarily of which listed mixture?

[WBCS Prelims — 2019]

(A) Carbon monoxide, methane and hydrogen

(B) Carbon dioxide, methane and hydrogen

(D) Carbon dioxide, ethane and hydrogen

Answer: (B) Carbon dioxide, methane and hydrogen

Explanation: Biogas produced by anaerobic digestion is dominated by methane and carbon dioxide, with possible small amounts of hydrogen and hydrogen sulphide. Ethane is not a principal component. The methane content is responsible for the fuel’s practical heating value.

161. Which one of the following is an aerobic process?

[RPSC Senior Teacher Science — 18 Feb 2019]

(A) Lactic acid fermentation

(B) Glycolysis

(D) Acetic acid fermentation

Answer: (D) Acetic acid fermentation

Explanation: Acetic acid bacteria oxidise ethanol to acetic acid in the presence of oxygen, making this an aerobic process. Alcoholic and lactic acid fermentations commonly occur under anaerobic conditions, while glycolysis itself does not require molecular oxygen.

160. Regarding the Petroleum and Natural Gas Regulatory Board:
1. It was India’s first regulatory body.
2. It seeks competitive gas markets.
3. Appeals go to the electricity appellate tribunal.

Which are correct?

[UPSC CSE Prelims — 2019]

(A) 1 and 2 only

(B) 2 and 3 only

(D) All three

Answer: (B) 2 and 3 only

Explanation: The board regulates specified activities in petroleum products and natural gas, supporting fair competition and consumer interests. It was not the first regulator created by India. Appeals are made to the relevant appellate tribunal under the statutory framework, so statements 2 and 3 are correct.

159. Which listed antibiotic is usually classed as narrow-spectrum?

[NEET Chemistry — 2019]

(A) Amoxicillin

(B) Chloramphenicol

(D) Ampicillin

Answer: (C) Penicillin G

Explanation: Penicillin G is mainly effective against susceptible Gram-positive organisms and is commonly classified as a narrow-spectrum antibiotic. Amoxicillin and ampicillin have extended antibacterial spectra, and chloramphenicol is broadly active. Actual clinical efficacy depends on organism susceptibility and resistance.

158. Match HDPE, polyacrylonitrile, novolac and nylon-6 with Ziegler–Natta catalyst, peroxide initiator, acid/base catalyst and high-temperature condensation respectively.

[JEE Main Online 10 Apr Evening Chemistry — 2019]

(A) HDPE-acid/base; PAN-condensation; novolac-peroxide; nylon-6-Ziegler–Natta

(B) HDPE-Ziegler–Natta; PAN-peroxide; novolac-acid/base; nylon-6-condensation

(D) HDPE-Ziegler–Natta; PAN-peroxide; novolac-condensation; nylon-6-acid/base

Answer: (B) HDPE-Ziegler–Natta; PAN-peroxide; novolac-acid/base; nylon-6-condensation

Explanation: High-density polyethylene can be made using coordination catalysts, while acrylonitrile commonly polymerises through radical initiation. Novolac phenolic resins form by catalysed condensation, and nylon-6 forms from caprolactam under suitable polymerisation conditions. The matching hinges on distinguishing polymer reaction types.

157. Which of the polymers listed is a condensation polymer?

[JEE Main Online 10 Apr Morning Chemistry — 2019]

(A) Neoprene

(B) Buna-S

(D) Teflon

Answer: (C) Nylon-6,6

Explanation: Nylon-6,6 has repeating amide linkages and forms by condensation between a diamine and a dicarboxylic acid. Buna-S, neoprene and Teflon are normally described as addition or chain-growth polymers. The presence of an amide backbone helps recognise nylon as a polyamide.

156. Which of the following is a thermosetting polymer?

[RPSC Senior Teacher Science — 01 Nov 2018]

(A) Terylene

(B) Polystyrene

(D) Neoprene

Answer: (C) Bakelite

Explanation: Bakelite is a cross-linked phenol-formaldehyde resin. Once cured, its network cannot simply be melted and reshaped like many thermoplastic polymers. Terylene and polystyrene are thermoplastics, while neoprene is an elastomer used for its flexible properties.

155. Which polymer used in paints is synthesised using ethylene glycol and phthalic acid?

[RPSC Senior Teacher Science — 01 Nov 2018]

(A) Dacron

(B) Bakelite

(D) Glyptal

Answer: (D) Glyptal

Explanation: Glyptal is an alkyd or polyester resin obtained by condensation of ethylene glycol with phthalic acid. Its film-forming properties support use in paints and surface coatings. Dacron and Bakelite involve different monomer combinations.

154. What is the chemical nature of vinegar?

[WBCS Prelims — 2018]

(A) Sodium nitrate

(B) Dilute acetic acid

(D) Calcium

Answer: (B) Dilute acetic acid

Explanation: Vinegar is a dilute aqueous solution of acetic acid, also called ethanoic acid, CH₃COOH. Its acidity gives vinegar its sour taste and helps preserve foods. It is produced commercially through biological oxidation of ethanol by acetic acid bacteria.

153. What does PVC stand for in the plastics industry?

[WBCS Prelims — 2018]

(A) Polyvinyl chloride

(B) Polyvinyl carbonate

(D) Phospho vinyl chloride

Answer: (A) Polyvinyl chloride

Explanation: PVC is polyvinyl chloride, a widely used synthetic thermoplastic formed from vinyl chloride monomers. It is chemically resistant and can be formulated as either rigid or flexible material. Familiar applications include pipes, cable insulation, flooring and protective coverings.

152. Adding a non-volatile solute to benzene at 30°C causes its vapour pressure to:

[RPSC Senior Teacher Science — 01 Nov 2018]

(A) Increase

(B) Decrease

(D) Depend only upon the solute

Answer: (B) Decrease

Explanation: Adding a non-volatile solute reduces the mole fraction of benzene in the liquid phase. Under ideal-solution conditions, Raoult’s law predicts a proportional reduction in the solvent vapour pressure. Thus the solution has a lower vapour pressure than pure benzene.

151. Which of the following is a renewable energy source?

[CGPSC Civil Service Prelims — 2018]

(A) Coal

(B) Petroleum

(D) Kerosene

Answer: (C) Biomass

Explanation: Biomass comes from recently living material and may be replenished through sustainable growth and waste recovery. It can supply combustible solids, biogas and some liquid biofuels. Coal, petroleum and kerosene are fossil-derived, non-renewable sources over human timescales.

150. Which claim about polymer growth is false?

[JEE Main Online 15 Apr Evening Chemistry — 2018]

(A) Step-growth polymerisation generally uses bifunctional monomers

(B) Nylon-6 can form by a step-growth pathway

(D) Chain-growth reactions can form only homopolymers

Answer: (D) Chain-growth reactions can form only homopolymers

Explanation: Chain-growth reactions can combine one monomer type into a homopolymer or multiple monomer types into a copolymer, as in styrene-butadiene rubber. Therefore claiming that chain-growth reactions produce homopolymers only is false. Step-growth chemistry commonly uses bifunctional monomers that join progressively.

149. Which alkene produces acetone on ozonolysis?

[RPSC Senior Teacher Science — 01 Jul 2017]

(A) But-2-ene

(B) But-1-ene

(D) Propene

Answer: (C) 2,3-dimethylbut-2-ene

Explanation: Ozonolysis cleaves the carbon-carbon double bond and converts its two ends into carbonyl-containing fragments. In 2,3-dimethylbut-2-ene, each double-bond carbon carries two methyl groups, so cleavage gives acetone. The alternative alkenes yield different aldehyde or ketone products.

148. With reference to algae biofuels:
1. Production is possible only in seas.
2. High technical expertise is needed.
3. Large installations can raise ecological concerns.

Which statements are correct?

[UPSC CSE Prelims — 2017]

(A) 1 and 2 only

(B) 2 and 3 only

(D) 1, 2 and 3

Answer: (B) 2 and 3 only

Explanation: Algae can be cultivated in freshwater, saline environments or engineered land-based systems; production is not restricted to seas. However, converting algae into commercially viable fuel requires technological expertise, and large facilities can present resource-use and environmental challenges. Thus statements 2 and 3 are correct.

147. Regarding the Climate and Clean Air Coalition:
1. It is a G20-only initiative.
2. It targets methane, black carbon and hydrofluorocarbons.

Which is correct?

[UPSC CSE Prelims — 2017]

(A) 1 only

(B) 2 only

(D) Neither 1 nor 2

Answer: (B) 2 only

Explanation: The coalition was launched through cooperation among multiple countries and international partners rather than as a G20-only institution. It seeks to reduce short-lived climate pollutants such as methane, black carbon and hydrofluorocarbons, thereby improving air quality and mitigating near-term warming.

146. What is the principal action of the chloroxylenol–terpineol mixture?

[NEET Chemistry — 2017]

(A) Antiseptic

(B) Antipyretic

(D) Analgesic

Answer: (A) Antiseptic

Explanation: Chloroxylenol is a phenolic antibacterial compound, and terpineol is a terpene alcohol used in some disinfectant mixtures. Together they provide antiseptic action that limits microbial growth on appropriate surfaces or tissues. They are not chiefly fever reducers, systemic antibiotics or pain medicines.

145. Formation of which listed polymer involves hydrolysis of a cyclic monomer?

[JEE Main Offline Chemistry — 2017]

(A) Bakelite

(B) Nylon-6,6

(D) Nylon-6

Answer: (D) Nylon-6

Explanation: Nylon-6 can be produced by ring-opening chemistry of caprolactam, including pathways involving water-mediated hydrolysis to aminocaproic acid followed by polymer formation. Nylon-6,6 and Terylene generally arise from condensation of two complementary bifunctional monomers. The cyclic monomer distinguishes nylon-6.

144. Which statements about vinegar are correct?
A. Sugarcane juice can be fermented to make vinegar.
B. Vinegar contains acetic acid.
C. Its characteristic acid is benzoic acid.
D. It preserves food.

[RPSC RAS Prelims — 2016]

(A) A, C and D

(B) A, B and D

(D) B, C and D

Answer: (B) A, B and D

Explanation: Fermentation of sugar-rich feedstock can yield ethanol, which bacteria convert into acetic acid. Vinegar therefore contains ethanoic rather than benzoic acid as its characteristic acid. Its acidic environment inhibits many spoilage microbes, making statements A, B and D correct.

143. What does the abbreviation PVC mean in the plastics industry?

[WBCS Prelims — 2016]

(A) Phospho vinyl chloride

(B) Polyvinyl carbonate

(D) Polyvinyl phosphate

Answer: (C) Polyvinyl chloride

Explanation: PVC refers to polyvinyl chloride, a thermoplastic formed by polymerising vinyl chloride. Because of its durability and ease of processing it is widely used in fittings, pipes and electrical insulation. This is a separate year-specific examination occurrence from similar PVC questions.

142. Which gases are included in the urban Air Quality Index: 1 CO₂, 2 CO, 3 NO₂, 4 SO₂, 5 methane?

[UPSC CSE Prelims — 2016]

(A) 1, 2 and 3 only

(B) 2, 3 and 4 only

(D) All five

Answer: (B) 2, 3 and 4 only

Explanation: India’s National Air Quality Index monitors pollutants including carbon monoxide, nitrogen dioxide and sulphur dioxide. Carbon dioxide and methane are important greenhouse gases but are not among the standard AQI component pollutants. Thus the correct gas numbers are 2, 3 and 4.

141. Which medicine among these is an analgesic?

[NEET Phase 1 Chemistry — 2016]

(A) Streptomycin

(B) Chloromycetin

(D) Penicillin

Answer: (C) Novalgin

Explanation: Novalgin is associated with metamizole, an analgesic and antipyretic compound. Streptomycin, chloromycetin and penicillin are antibiotics used against susceptible bacterial infections. Recognising therapeutic drug classes is one application of organic chemistry and the study of biologically active molecules.

140. Which statement about low-density polythene is false?

[JEE Main Offline Chemistry — 2016]

(A) It can be manufactured under high pressure

(B) It is usually an electrical insulator

(D) It is chiefly the material of rigid buckets and dustbins

Answer: (D) It is chiefly the material of rigid buckets and dustbins

Explanation: Low-density polyethylene is highly branched and is commonly used for flexible films and bags. High-density polyethylene is better suited to rigid articles such as buckets and dustbins. LDPE can be made by high-pressure radical polymerisation and normally has poor electrical conductivity.

139. Which polymer can be prepared by free-radical addition polymerisation?

[JEE Main Online 10 Apr Morning Chemistry — 2016]

(A) Teflon

(B) Terylene

(D) Nylon-6,6

Answer: (A) Teflon

Explanation: Teflon, or polytetrafluoroethylene, is an addition polymer obtainable through chain-growth reactions of tetrafluoroethylene. Terylene and nylon-6,6 are condensation polymers, while melamine-formaldehyde resin also forms through a different network-forming process. Monomer structure determines suitable polymerisation mechanisms.

138. Which element forms the fundamental basis of all organic compounds?

[BPSC Prelims — 56th to 59th Combined Examination (2015)]

(A) Nitrogen

(B) Oxygen

(D) Brimstone

Answer: (C) Carbon

Explanation: Organic compounds are broadly defined by carbon-containing covalent molecular structures, frequently with hydrogen and also sometimes oxygen, nitrogen or other elements. Carbon can form four bonds and link repeatedly with itself. This combination supports the large diversity of biological and synthetic organic molecules.

137. Which element is most fundamental to the structure of all bio-compounds?

[UPPCS Mains — 2015]

(A) Sulphur

(B) Carbon

(D) Nitrogen

Answer: (B) Carbon

Explanation: Carbon forms the core skeleton of carbohydrates, lipids, proteins and nucleic acids, permitting numerous stable covalent structures. Oxygen and nitrogen are common in biomolecules, but not all compounds contain each of them. Carbon is the foundational element of organic biochemistry.

136. Coal, petroleum and natural gas are collectively examples of:

[WBCS Prelims — 2015]

(A) Fossil fuels

(B) Cryogenic fuels

(D) Radioactive fuels

Answer: (A) Fossil fuels

Explanation: Coal, crude petroleum and natural gas are fossil fuels formed from ancient organic matter under geological processes over millions of years. Natural gas is rich in methane; petroleum contains a mixture of hydrocarbons; and coal consists largely of carbon-rich material.

135. Which substituent is meta-directing in electrophilic aromatic substitution?

[RPSC Senior Teacher Science — 2015]

(A) –NH₂

(B) –SO₃H

(D) –C₂H₅

Answer: (B) –SO₃H

Explanation: The sulfonic acid group withdraws electron density from the benzene ring, destabilising ortho and para substitution pathways relative to meta attack. Hence –SO₃H is meta-directing. Amino, methoxy and alkyl groups generally favour ortho and para electrophilic aromatic substitution.

134. Neoprene synthetic rubber is polymerised from which monomer?

[RPSC Senior Teacher Science — 2015]

(A) Isoprene

(B) Chloroprene

(D) Acrylonitrile

Answer: (B) Chloroprene

Explanation: Neoprene, or polychloroprene, results from the polymerisation of chloroprene. It is an artificial elastomer noted for useful resistance to oil, weathering and many chemicals. Isoprene is associated with natural rubber, while caprolactam is used for nylon-6.

133. Which amino acid cannot be synthesised sufficiently by the human body and must be obtained from food?

[RPSC Senior Teacher Science — 2015]

(A) Glycine

(B) Alanine

(D) Proline

Answer: (C) Tryptophan

Explanation: Tryptophan is an essential amino acid needed from the diet because humans cannot synthesise it adequately. Glycine, alanine and proline can ordinarily be synthesised in the body. Amino acids contain both amino and carboxyl functional groups and form the building blocks of proteins.

132. What stereochemical result is most commonly observed for SN1 substitution at a chiral centre?

[AIPMT Chemistry — 2015]

(A) More inversion than retention, with partial racemisation

(B) Complete retention only

(D) Always precisely 50:50 racemisation

Answer: (A) More inversion than retention, with partial racemisation

Explanation: The SN1 mechanism forms a largely planar carbocation that can be attacked from either face. Solvent cages or ion-pair effects may shield one face, so a slight excess of inversion often occurs. The product can therefore show partial racemisation instead of perfect 50:50 mixing.

131. Which polymer is used in formulating paints and lacquers?

[JEE Main Offline Chemistry — 2015]

(A) Glyptal

(B) Polypropene

(D) Bakelite

Answer: (A) Glyptal

Explanation: Glyptal is an alkyd polyester resin produced from polyhydric alcohols and polybasic acids or anhydrides. Such resins are used as binding materials in protective coatings, paints and lacquers. Its film-forming characteristics distinguish it from ordinary packaging plastics.

130. Which of these medicines is NOT used to neutralise or suppress excess stomach acid?

[JEE Main Offline Chemistry — 2015]

(A) Cimetidine

(B) Ranitidine

(D) Aluminium hydroxide

Answer: (C) Phenelzine

Explanation: Phenelzine is a monoamine oxidase inhibitor prescribed for certain psychiatric disorders, not an acid-suppression medicine. Aluminium hydroxide neutralises gastric acid directly, while cimetidine and ranitidine reduce gastric acid secretion by blocking H₂ histamine receptors.

129. Which one of the following is not considered an explosive material in the given list?

[UPPSC Civil Service Prelims — 2014, Paper 1]

(A) Trinitrotoluene

(B) Dinitroglycerine

(D) Nitrochloroform

Answer: (D) Nitrochloroform

Explanation: The published examination key identifies nitrochloroform, also called chloropicrin, as the odd one out. It is chiefly known as a toxic fumigant rather than a conventional blasting explosive. The other options are associated with energetic nitrate or nitro compounds.

128. About coalbed methane and shale gas:
1. Shale gas contains only propane and butane.
2. India has no shale gas sources.

Which statements are correct?

[UPSC CSE Prelims — 24 Aug 2014]

(A) 1 only

(B) 2 only

(D) Neither 1 nor 2

Answer: (D) Neither 1 nor 2

Explanation: Coalbed methane and shale gas are unconventional sources of natural gas dominated by methane rather than solely propane and butane. Shale formations in India have been assessed for hydrocarbon potential, so the claim that no such sources exist is incorrect. Both statements are false.

127. Which pair of monomers produces the polyester Dacron?

[AIPMT Chemistry — 2014]

(A) Propylene and hydroquinone

(B) Benzoic acid and ethanol

(D) Benzoic acid and hydroquinone

Answer: (C) Terephthalic acid and ethylene glycol

Explanation: Dacron, or polyethylene terephthalate, is formed by reacting terephthalic acid with ethylene glycol to create ester links along the polymer chain. The rigid aromatic units and repeating ester groups provide useful strength and dimensional stability for textile fibres and packaging applications.

126. Which artificial sweetener is mainly stable under cold conditions rather than high cooking temperatures?

[AIPMT Chemistry — 2014]

(A) Saccharin

(B) Sucralose

(D) Alitame

Answer: (C) Aspartame

Explanation: Aspartame is a methyl ester of a dipeptide and can undergo hydrolysis or degradation on prolonged heating. Thus it is more suitable for cold foods and drinks than extended cooking. Saccharin and sucralose generally have better thermal stability in relevant applications.

125. Which of the following substances is a condensation polymer?

[JEE Main Offline Chemistry — 2014]

(A) Teflon

(B) Acrylonitrile

(D) Neoprene

Answer: (C) Dacron

Explanation: Dacron, a polyethylene terephthalate polyester, is classed as a condensation polymer formed from suitable diol and dicarboxylic-acid units. Teflon and neoprene form by chain-growth addition processes, while acrylonitrile is a monomer rather than the completed polymer.

124. Which reagent selectively oxidises a primary alcohol R–CH₂OH to an aldehyde R–CHO?

[JEE Main Offline Chemistry — 2014]

(A) Chromium trioxide

(B) Pyridinium chlorochromate

(D) Potassium dichromate

Answer: (B) Pyridinium chlorochromate

Explanation: Pyridinium chlorochromate, often abbreviated PCC, is a comparatively mild oxidising agent. Under anhydrous conditions it commonly stops oxidation of a primary alcohol at the aldehyde stage, whereas stronger aqueous oxidants may continue to the corresponding carboxylic acid.

123. ABS plastic is a:

[UPSC Engineering Services Mechanical — 2013, Paper 2]

(A) Monomer

(B) Copolymer

(D) Terpolymer

Answer: (D) Terpolymer

Explanation: ABS stands for acrylonitrile-butadiene-styrene. It contains three different monomer-derived components, so it is classified as a terpolymer. ABS is an engineering thermoplastic valued for impact resistance and processability; it is not a single monomer or homopolymer.

122. Euro vehicle-emission standards cover which gases?

[UPPSC Civil Service Prelims — 2013, Paper 1]

(A) Carbon monoxide

(B) Hydrocarbons

(D) All of the above

Answer: (D) All of the above

Explanation: Vehicle emission standards regulate multiple pollutant categories, including carbon monoxide, unburned hydrocarbons and nitrogen oxides. Hydrocarbon emissions are particularly relevant to incomplete combustion of organic fuels. Their limits seek to reduce adverse impacts on air quality.

121. Consider:
1. Natural gas occurs in Gondwana beds.
2. Mica is abundant in Kodarma.
3. Dharwar rocks are famous for petroleum.

Which is correct?

[UPSC CSE Prelims — 2013]

(A) 1 and 2

(B) 2 only

(D) None

Answer: (B) 2 only

Explanation: Kodarma has historically been associated with mica deposits. Gondwana formations are best known for coal, whereas India’s principal conventional petroleum and natural gas basins occur in different geological settings. The Dharwar rock system is mineral-rich but not noted for petroleum deposits.

120. Which statement about common antiseptics and disinfectants is incorrect?

[NEET Chemistry — 2013]

(A) Dilute boric acid and hydrogen peroxide are strong antiseptics

(B) Disinfectants may harm living tissues

(D) Chlorine and iodine may be used for disinfection

Answer: (A) Dilute boric acid and hydrogen peroxide are strong antiseptics

Explanation: Dilute boric acid and hydrogen peroxide are typically considered mild rather than strong antiseptics. Many disinfectants are harmful to living tissue, whereas antiseptics are formulated for limited tissue contact. Phenol concentration and the chemistry of halogens affect their antimicrobial applications.

119. Traditional Dettol antiseptic contains which principal pair of organic compounds?

[NEET Karnataka Chemistry — 2013]

(A) Chloroxylenol and bithionol

(B) Chloroxylenol and terpineol

(D) Terpineol and bithionol

Answer: (B) Chloroxylenol and terpineol

Explanation: Traditional Dettol formulations contain chloroxylenol, a substituted phenolic antimicrobial, and terpineol, an organic terpene alcohol. Both names identify aromatic or alcohol functional chemistry relevant to disinfectants. Commercial formulations may change, but this pair is the examination’s prescribed answer.

118. Which type of alcohol reacts most rapidly in the Lucas test, and through what mechanism?

[JEE Main Offline Chemistry — 2013]

(A) Tertiary alcohol via SN1

(B) Secondary alcohol via SN2

(D) Secondary alcohol via SN1

Answer: (A) Tertiary alcohol via SN1

Explanation: Tertiary alcohols convert rapidly to alkyl chlorides in concentrated hydrochloric acid and zinc chloride. Their relatively stable tertiary carbocation permits a fast SN1 mechanism. Secondary alcohols react more slowly and primary alcohols usually show little immediate turbidity in the conventional test.

117. TNT (trinitrotoluene) is a/an:

[Chhattisgarh Police Sub-Inspector Prelims — 2012]

(A) Fertilizer

(B) Explosive

(D) Medicine

Answer: (B) Explosive

Explanation: TNT is the common abbreviation of trinitrotoluene, an aromatic nitro compound used as an explosive. It is not categorised as a fertiliser, insecticide or medicine. This basic identification often appears in general science and awareness examinations.

116. Which set of elements was considered primarily responsible for the origin of life on Earth?

[UPSC CSE Prelims — 2012]

(A) Hydrogen, oxygen and sodium

(B) Carbon, hydrogen and nitrogen

(D) Carbon, hydrogen and potassium

Answer: (B) Carbon, hydrogen and nitrogen

Explanation: Carbon, hydrogen and nitrogen are core elements of biological molecules and prebiotic organic chemistry. Oxygen, phosphorus and sulphur are also vital to modern life. Among the offered combinations, carbon, hydrogen and nitrogen best represent the basic chemical constituents central to the origin-of-life discussion.

115. Which reagent converts 2-hexyne into trans-2-hexene?

[AIEEE Chemistry — 2012]

(A) Hydrogen with platinum

(B) Lithium in liquid ammonia

(D) Lithium aluminium hydride

Answer: (B) Lithium in liquid ammonia

Explanation: Dissolving-metal reduction of an alkyne using lithium in liquid ammonia adds hydrogen in an overall anti fashion, producing a trans-alkene. Lindlar-type poisoned palladium catalysts instead favour cis-alkenes, while ordinary catalytic hydrogenation can reduce the multiple bond further to an alkane.

114. Which statement about polymers is incorrect?

[AIPMT Prelims Chemistry — 2012]

(A) Artificial silk can be made from cellulose

(B) Nylon-6,6 is an elastomer

(D) Both starch and cellulose are glucose polymers

Answer: (B) Nylon-6,6 is an elastomer

Explanation: Nylon-6,6 is a synthetic polyamide fibre, not an elastomer like natural rubber. Artificial silk or rayon is manufactured from processed cellulose, and both starch and cellulose consist of glucose-derived units. Their differing glycosidic linkages lead to markedly different physical properties.

113. Which of these is not a condensation polymer?

[AIPMT Prelims Chemistry — 2012]

(A) Melamine resin

(B) Glyptal

(D) Neoprene

Answer: (D) Neoprene

Explanation: Neoprene forms by addition polymerisation of chloroprene, an unsaturated organic monomer. Dacron and Glyptal are polyesters made by condensation reactions, while melamine-formaldehyde resins also arise through condensation chemistry. The polymerisation mechanism therefore separates neoprene from the other listed materials.

112. Chloramphenicol belongs to which drug category?

[AIPMT Mains Chemistry — 2012]

(A) Antifertility medicine

(B) Antihistamine

(D) Broad-spectrum antibiotic

Answer: (D) Broad-spectrum antibiotic

Explanation: Chloramphenicol is a broad-spectrum antibiotic that inhibits bacterial protein synthesis by acting on ribosomes. It is chemically distinct from antihistamines and antiseptics. Due to potentially serious adverse effects, including bone-marrow toxicity, its use is restricted and monitored in many clinical settings.

111. Which reagent best initiates cationic polymerisation among the choices?

[AIEEE Chemistry — 2012]

(A) LiAlH₄

(B) HNO₃

(D) Butyllithium

Answer: (C) AlCl₃

Explanation: Aluminium chloride is a Lewis acid that can generate or stabilise electrophilic initiating species for cationic chain polymerisation. Butyllithium is more typically associated with anionic reactions, and lithium aluminium hydride is a reducing agent. The initiating chemistry depends on the monomer and catalyst system.

110. Why is ortho-nitrophenol less soluble in water than its meta and para isomers?

[AIEEE Chemistry — 2012]

(A) It is more steam-volatile

(B) It has intramolecular hydrogen bonding

(D) It has a lower melting point

Answer: (B) It has intramolecular hydrogen bonding

Explanation: Ortho-nitrophenol can form an intramolecular hydrogen bond between its neighbouring hydroxyl and nitro groups. That internal interaction reduces its tendency to hydrogen-bond with surrounding water. Meta and para isomers are more available for intermolecular hydrogen bonding and are relatively more soluble.

109. Aspirin is chemically known as what?

[AIEEE Chemistry — 2012]

(A) Acetylsalicylic acid

(B) Phenyl salicylate

(D) Methylsalicylic acid

Answer: (A) Acetylsalicylic acid

Explanation: Aspirin is acetylsalicylic acid, an acetylated derivative of salicylic acid. It contains an aromatic ring, a carboxylic acid and an ester group. Aspirin has analgesic and antipyretic actions and can also inhibit platelet aggregation at appropriate doses.

108. Formaldehyde among the products of alkene ozonolysis confirms the presence of which structural feature?

[AIEEE Chemistry — 2011]

(A) Terminal vinyl group

(B) Isopropyl group

(D) Two internal carbon-carbon double bonds

Answer: (A) Terminal vinyl group

Explanation: Ozonolysis cleaves carbon-carbon double bonds to give carbonyl compounds. A terminal methylene unit, CH₂=, produces formaldehyde after reductive work-up. Thus the observation indicates a terminal alkene or vinyl-type structural group rather than merely an isopropyl group or an alkyne.

107. Which material among the following is a polyester?

[AIPMT Prelims Chemistry — 2011]

(A) Terylene

(B) Bakelite

(D) Nylon-6,6

Answer: (A) Terylene

Explanation: Terylene, also known as PET or Dacron, contains recurring ester linkages formed from ethylene glycol and terephthalic acid. Nylon-6,6 is a polyamide, whereas Bakelite and melamine resins are generally cross-linked thermosetting polymers. Polyester classification depends on the ester bonds in the backbone.

106. Which one is used as an antihistamine?

[AIPMT Prelims Chemistry — 2011]

(A) Chloramphenicol

(B) Diphenhydramine

(D) Omeprazole

Answer: (B) Diphenhydramine

Explanation: Diphenhydramine blocks histamine H1 receptors and is used to relieve allergy symptoms. Chloramphenicol is an antibiotic, norethindrone is a progestin and omeprazole reduces gastric acid secretion. Their distinct organic functional groups support different biological targets and therapeutic applications.

105. Reaction of phenol with a potassium bromide–potassium bromate mixture gives chiefly which brominated phenol?

[AIEEE Chemistry — 2011]

(A) 3-Bromophenol

(B) 4-Bromophenol

(D) 2-Bromophenol

Answer: (C) 2,4,6-Tribromophenol

Explanation: Phenol strongly activates its aromatic ring by resonance donation from the hydroxyl group. Brominating species generated from the listed reagents can therefore substitute at both ortho positions and the para position, producing 2,4,6-tribromophenol under the stated conditions.

104. Which of these compounds is the strongest acid?

[AIEEE Chemistry — 2011]

(A) Formic acid

(B) 2-Chlorobutanoic acid

(D) Acetic acid

Answer: (B) 2-Chlorobutanoic acid

Explanation: An electronegative chlorine substituent withdraws electron density through the sigma-bond framework. Its acid-strengthening effect is greatest when chlorine lies adjacent to the carboxyl group. Thus 2-chlorobutanoic acid is more acidic than the distant 4-chloro isomer and unsubstituted acids.

103. What is obtained by reacting sodium ethoxide with acetyl chloride?

[AIEEE Chemistry — 2011]

(A) Butan-2-one

(B) Ethyl chloride

(D) Diethyl ether

Answer: (C) Ethyl ethanoate

Explanation: Ethoxide ion attacks the carbonyl carbon of acetyl chloride. Chloride is expelled through nucleophilic acyl substitution, creating the ester ethyl ethanoate, also called ethyl acetate. This is an ester-forming reaction of an acyl chloride with an alkoxide.

102. Which alcohol is formed when chloral (CCl₃CHO) undergoes the Cannizzaro reaction in strong alkali?

[AIEEE Chemistry — 2011]

(A) Trichloromethanol

(B) 2,2,2-Trichloropropanol

(D) 2,2,2-Trichloroethanol

Answer: (D) 2,2,2-Trichloroethanol

Explanation: Chloral lacks an alpha hydrogen suitable for an aldol condensation and can undergo Cannizzaro disproportionation. One chloral molecule gives a trichloroacetate salt, while another is reduced to trichloroethanol, CCl₃CH₂OH, through intermolecular hydride transfer.

101. What is formed when glycerol is treated with excess hydrogen iodide?

[AIPMT Mains Chemistry — 2010]

(A) 2-Iodopropane

(B) Allyl iodide

(D) Glycerol triiodide

Answer: (A) 2-Iodopropane

Explanation: Excess hydrogen iodide can replace and reduce the hydroxyl-containing framework of glycerol under strongly reducing conditions. The net transformation gives 2-iodopropane in the examination scheme. The reaction should not be confused with simple single-step substitution of every hydroxyl group by iodine.

100. Match A butan-1-amine, B propyne, C methyl propanoate and D propan-2-ol

with 1 alkaline hydrolysis, 2 carbylamine test, 3 ammoniacal silver nitrate, 4 Lucas reagent.

[AIPMT Mains Chemistry — 2010]

(A) A-2, B-1, C-4, D-3

(B) A-3, B-2, C-1, D-4

(D) A-4, B-2, C-3, D-1

Answer: (C) A-2, B-3, C-1, D-4

Explanation: A primary amine gives the carbylamine test, and terminal propyne forms a precipitate with ammoniacal silver nitrate. The ester methyl propanoate undergoes alkaline hydrolysis, while the secondary alcohol propan-2-ol reacts with Lucas reagent with observable turbidity after a short time.

99. Arrange the acidity of I cyclohexanol, II acetic acid, III picric acid and IV phenol in decreasing order.

[AIPMT Prelims Chemistry — 2010]

(A) III > II > IV > I

(B) II > III > I > IV

(D) III > IV > II > I

Answer: (A) III > II > IV > I

Explanation: Picric acid is strongly acidic because three nitro groups stabilise its conjugate base. Acetic acid is stronger than phenol owing to carboxylate resonance stabilisation. Cyclohexanol is a much weaker acid than phenol. Therefore the descending order is picric, acetic, phenol, cyclohexanol.

98. Rank phenol I, methylphenol II, m-nitrophenol III and p-nitrophenol IV by decreasing acidity.

[AIPMT Prelims Chemistry — 2010]

(A) IV > III > I > II

(B) III > IV > I > II

(D) II > I > III > IV

Answer: (A) IV > III > I > II

Explanation: Nitro groups increase phenol acidity by withdrawing electron density; a para nitro group also offers strong resonance stabilisation of the phenoxide ion. A methyl group donates electron density and reduces acidity. Thus para-nitrophenol exceeds meta-nitrophenol, followed by phenol and methylphenol.

97. Which medicinal compound is classified as a tranquiliser?

[AIPMT Prelims Chemistry — 2010]

(A) Promethazine

(B) Valium

(D) Mifepristone

Answer: (B) Valium

Explanation: Valium is diazepam, a benzodiazepine medicine with anxiolytic and sedative actions. Promethazine is chiefly an antihistamine, naproxen relieves pain and inflammation, and mifepristone is an antiprogestogen. Molecular structure and target-receptor binding explain why these drugs have different effects.

96. Which polymer is strengthened by pronounced intermolecular hydrogen bonding?

[AIEEE Chemistry — 2010]

(A) Teflon

(B) Nylon-6,6

(D) Natural rubber

Answer: (B) Nylon-6,6

Explanation: Nylon-6,6 carries polar amide groups along its chains. Carbonyl oxygen and amide hydrogen atoms of neighbouring chains form hydrogen bonds, helping give the material high tensile strength. Polystyrene, Teflon and natural rubber lack a comparably dense pattern of hydrogen-bonding amide groups.

95. Which alcohol reacts fastest with Lucas reagent, concentrated HCl and anhydrous ZnCl₂?

[AIEEE Chemistry — 2010]

(A) Butan-2-ol

(B) 2-Methylpropan-2-ol

(D) Butan-1-ol

Answer: (B) 2-Methylpropan-2-ol

Explanation: Tertiary alcohols such as tert-butanol react rapidly with Lucas reagent because the reaction can proceed through a relatively stable tertiary carbocation. Secondary alcohols react more slowly, and primary alcohols are typically much slower under ordinary test conditions.

94. Which symmetric alkene gives two ethanal molecules, each of mass 44 u, on reductive ozonolysis?

[AIEEE Chemistry — 2010]

(A) Propene

(B) But-1-ene

(D) Ethene

Answer: (C) But-2-ene

Explanation: But-2-ene has the structure CH₃CH=CHCH₃. Cleaving its central double bond yields two identical CH₃CHO molecules. Each ethanal molecule has molecular mass 44 u, satisfying both the symmetry and product-mass conditions in the question.

93. Which one of these substances is used as an explosive?

[UPSC CSE Prelims — 2009]

(A) Phosphorus trichloride

(B) Mercuric oxide

(D) Nitroglycerine

Answer: (D) Nitroglycerine

Explanation: Nitroglycerine is a highly energetic nitrate ester associated with commercial explosive applications. Graphite is a carbon allotrope, mercuric oxide is a metal oxide, and phosphorus trichloride is a reactive inorganic reagent. Of these substances, nitroglycerine is the explosive specified in the question.

92. During generation of the nitrating electrophile using HNO3 and concentrated H2SO4, how does nitric acid behave?

[AIPMT Chemistry — 2009]

(A) As an acid donating a proton

(B) As a base accepting a proton

(D) As a reducing agent

Answer: (B) As a base accepting a proton

Explanation: Concentrated sulphuric acid protonates nitric acid in the nitrating mixture. Protonated nitric acid then loses water to form the nitronium ion, NO₂⁺, which attacks an aromatic ring. Because it initially accepts a proton, nitric acid acts as a Brønsted base in this step.

91. Which of these organic drugs is employed as a tranquiliser?

[AIPMT Chemistry — 2009]

(A) Naproxen

(B) Tetracycline

(D) Equanil

Answer: (D) Equanil

Explanation: Equanil is a brand name associated with meprobamate, a sedative and anxiolytic drug historically classified among tranquilisers. Naproxen is a non-steroidal anti-inflammatory drug, tetracycline is an antibiotic, and chlorpheniramine is an antihistamine. Their different actions arise from different pharmacological structures.

90. Treatment of phenol with sodium hydroxide and then carbon dioxide gives which acid after work-up?

[AIEEE Chemistry — 2009]

(A) Benzoic acid

(B) Salicylaldehyde

(D) Phthalic acid

Answer: (C) Salicylic acid

Explanation: The Kolbe–Schmitt reaction introduces a carboxyl group onto a phenoxide ring, mainly at the ortho position under suitable conditions. Acidification produces salicylic acid, also known as 2-hydroxybenzoic acid. The reaction connects aromatic phenols and important organic carboxylic acids.

89. Which liquid forms a fruity-smelling ester when mixed with ethanol and concentrated sulphuric acid?

[AIEEE Chemistry — 2009]

(A) Methanol

(B) Formaldehyde

(D) Acetic acid

Answer: (D) Acetic acid

Explanation: Acetic acid reacts reversibly with ethanol in the presence of concentrated sulphuric acid to form ethyl ethanoate and water. Ethyl ethanoate is a volatile ester with a characteristic fruity odour. Sulphuric acid catalyses the Fischer esterification reaction.

88. What is the rate-determining step of the Cannizzaro reaction of benzaldehyde?

[AIEEE Chemistry — 2009]

(A) Hydride transfer to another carbonyl molecule

(B) Removal of a proton from a carboxylic acid group

(D) Removal of the benzyl alcohol proton

Answer: (A) Hydride transfer to another carbonyl molecule

Explanation: Hydroxide first attacks the benzaldehyde carbonyl, creating a tetrahedral intermediate. The crucial slow step transfers a hydride from that intermediate to a second aldehyde molecule. This produces the reduced alcohol and an oxidised carboxylate after the subsequent proton-transfer steps.

87. What is Bisphenol A (BPA)?

[UPSC CSE Prelims — 2008]

(A) A diagnostic test for cancer

(B) A test for performance-enhancing drugs in athletes

(D) A specialised steel alloy

Answer: (C) A chemical used to develop food-packaging materials

Explanation: Bisphenol A is an organic industrial compound used to produce polycarbonate plastic and epoxy resins. Certain containers and protective food-can coatings historically used these materials. BPA is not a medical test or steel alloy, and its possible hormonal effects have prompted safety scrutiny.

86. A mixture of which gases is responsible for most explosions in coal mines?

[UPSC CSE Prelims — 2008]

(A) Hydrogen and oxygen

(B) Oxygen and acetylene

(D) Carbon dioxide and methane

Answer: (C) Methane and air

Explanation: Coal seams may release methane, a flammable hydrocarbon. When it accumulates with oxygen-containing air within an ignitable range, an ignition source can trigger a mine explosion. Ventilation and gas detection are crucial safeguards. Carbon dioxide itself does not act as a combustible fuel.

85. Reductive ozonolysis of but-2-ene with ozone followed by zinc and water gives which product?

[AIEEE Chemistry — 2008]

(A) Propanal

(B) Propanone

(D) Ethanal

Answer: (D) Ethanal

Explanation: But-2-ene has a symmetrical internal double bond. Cleavage of this bond by ozone followed by a reductive work-up gives two molecules of ethanal. Ketones or larger aldehydes would require differently substituted double-bonded carbons in the starting alkene.

84. Nitration of toluene, reduction of the nitro groups, diazotisation, and treatment with cuprous bromide produces which mixture?

[AIEEE Chemistry — 2008]

(A) Ortho- and para-bromotoluene

(B) Ortho- and para-dibromobenzene

(D) Ortho- and meta-bromotoluene

Answer: (A) Ortho- and para-bromotoluene

Explanation: Toluene nitration initially produces mainly ortho and para derivatives. Reduction converts nitro groups to amino groups; diazotisation followed by the Sandmeyer reaction substitutes bromine for the amino-derived diazonium group. Consequently, the final mixture mainly contains ortho- and para-bromotoluenes.

83. Which statement about natural and synthetic rubber is false?

[AIPMT Chemistry — 2008]

(A) Buna-S is a butadiene-styrene copolymer

(B) Natural rubber is a 1,4-polymer of isoprene

(D) Natural rubber has a trans configuration at every double bond

Answer: (D) Natural rubber has a trans configuration at every double bond

Explanation: Natural rubber is predominantly cis-1,4-polyisoprene, not the trans form described in the last statement. The cis configuration contributes to elasticity. Buna-S is a butadiene-styrene copolymer, and vulcanisation forms sulphur cross-links that improve toughness and resilience.

82. Which aldehyde reacts with phenol to produce Bakelite resin?

[AIEEE Chemistry — 2008]

(A) Ethylene glycol

(B) Acetaldehyde

(D) Formaldehyde

Answer: (D) Formaldehyde

Explanation: Bakelite is a phenol-formaldehyde thermosetting resin. Reactions of phenolic aromatic sites with formaldehyde lead to methylene-linked networks that become rigid on curing. Acetone is a ketone and ethylene glycol is a diol, so neither is the standard aldehyde used for this polymer.

81. By which other name is the compound RDX known?

[UPSC CSE Prelims — 2007]

(A) Cyanohydrin

(B) Dextran

(D) Cyclonite

Answer: (D) Cyclonite

Explanation: Cyclonite is a common alternative name for RDX, an energetic cyclic nitramine compound. The other options designate unrelated substances: cyanohydrins are compounds bearing hydroxyl and cyano groups, dextran is a polysaccharide, and cyclohexane is a saturated six-carbon hydrocarbon.

80. Which reaction gives 2,2-dibromopropane?

[AIEEE Chemistry — 2007]

(A) Propene with one equivalent of HBr

(B) Propyne with two equivalents of HBr

(D) Ethyne with two equivalents of HBr

Answer: (B) Propyne with two equivalents of HBr

Explanation: Adding two equivalents of hydrogen bromide to the terminal alkyne propyne follows the usual Markovnikov orientation. Both bromine atoms ultimately become attached to the middle carbon, yielding the geminal dibromide 2,2-dibromopropane. The other combinations do not yield that structural product.

79. Reaction of toluene with chlorine in the presence of ferric chloride mainly forms what?

[AIEEE Chemistry — 2007]

(A) Benzoyl chloride

(B) Benzyl chloride

(D) Meta-chlorotoluene

Answer: (C) Ortho- and para-chlorotoluene

Explanation: Ferric chloride promotes electrophilic aromatic chlorination. The methyl group already attached to benzene activates the ring and directs substitution preferentially to its ortho and para positions. Side-chain chlorination to benzyl chloride is more characteristic of radical conditions such as ultraviolet irradiation.

78. Which C₅H₁₀ compound produces acetone on ozonolysis?

[AIPMT Chemistry — 2007]

(A) 3-Methyl-1-butene

(B) Cyclopentane

(D) 2-Methyl-2-butene

Answer: (D) 2-Methyl-2-butene

Explanation: Ozonolysis cleaves an alkene double bond, converting each of its carbons into a carbonyl carbon. In 2-methyl-2-butene, one alkene carbon bears two methyl groups and therefore becomes acetone. The other cleavage fragment is ethanal.

77. Which listed polymer is manufactured by condensation polymerisation?

[AIPMT Chemistry — 2007]

(A) Teflon

(B) Natural rubber

(D) Nylon-6,6

Answer: (D) Nylon-6,6

Explanation: Nylon-6,6 is a polyamide produced by condensation between a diamine and a dicarboxylic acid, creating amide links while eliminating small molecules. Teflon and natural rubber form by addition polymerisation. Styrene is a monomer, rather than the requested condensation polymer.

76. An optically active compound shows zero net rotation despite having a chiral structure. What may explain this?

[AIPMT Chemistry — 2007]

(A) It must be a meso compound

(B) There is no compound in the solvent

(D) The molecule must be achiral

Answer: (C) The sample may be a racemic mixture

Explanation: An equimolar mixture of two enantiomers is racemic. Each enantiomer rotates plane-polarised light by an equal magnitude in the opposite direction, so the net observed rotation is zero. The underlying molecules remain chiral even though their combined solution is optically inactive.

75. What is the increasing nucleophilicity order of Cl⁻, Br⁻ and I⁻ in a polar protic solvent?

[AIPMT Chemistry — 2007]

(A) Cl⁻ < Br⁻ < I⁻

(B) I⁻ < Cl⁻ < Br⁻

(D) I⁻ < Br⁻ < Cl⁻

Answer: (A) Cl⁻ < Br⁻ < I⁻

Explanation: In a polar protic medium smaller halide ions are more strongly solvated by hydrogen bonding, reducing their availability to attack an electrophile. The larger iodide ion is less tightly solvated and is more nucleophilic than bromide or chloride. Solvent identity is essential to this trend.

74. Order the decreasing electrophilic substitution reactivity of benzene I, toluene II, chlorobenzene III and phenol IV.

[AIPMT Chemistry — 2007]

(A) II > IV > I > III

(B) IV > III > II > I

(D) I > II > III > IV

Answer: (C) IV > II > I > III

Explanation: The hydroxyl group in phenol strongly donates electrons by resonance, activating the ring. A methyl group in toluene also activates the ring, but less strongly. Benzene is the baseline, while chlorine deactivates its ring inductively. Thus phenol reacts fastest and chlorobenzene slowest.

73. Reduction with LiAlH4 of which compound can give a secondary amine?

[AIPMT Chemistry — 2007]

(A) Methyl isocyanide

(B) Acetamide

(D) Nitroethane

Answer: (A) Methyl isocyanide

Explanation: Isocyanides have the general structure R–N≡C and can be reduced to N-methyl-substituted amines. Methyl isocyanide therefore produces dimethylamine, a secondary amine. Acetamide, acetonitrile and nitroethane instead normally provide primary amines when fully reduced.

72. Ethanol is converted to ethyl iodide, then to its Grignard reagent and reacted with formaldehyde followed by water. Which alcohol forms?

[AIEEE Chemistry — 2007]

(A) Butanal

(B) Butan-1-ol

(D) Propanal

Answer: (C) Propan-1-ol

Explanation: Converting ethanol to an ethyl halide and then its Grignard reagent makes an ethyl nucleophile. Addition to formaldehyde introduces one further carbon atom, producing a primary propyl alcohol after work-up. This carbon-chain extension is characteristic of formaldehyde reactions with Grignard reagents.

71. What is formed by oxidising ethylbenzene with hot potassium permanganate?

[AIEEE Chemistry — 2007]

(A) Benzophenone

(B) Acetophenone

(D) Benzyl alcohol

Answer: (C) Benzoic acid

Explanation: Hot potassium permanganate oxidises an alkylbenzene side chain bearing a benzylic hydrogen to a carboxyl group. Ethylbenzene has such a hydrogen, so its two-carbon side chain is ultimately converted into the –COOH group of benzoic acid.

70. Which chemicals were used as dry-cleaning agents?
1. Benzene;
2. Carbon tetrachloride;
3. Sodium carbonate;
4. Trichloroethylene.

[UPSC CSE Prelims — 2006]

(A) 1 only

(B) 2 only

(D) 1, 2, 3 and 4

Answer: (C) 1, 2 and 4 only

Explanation: Benzene, carbon tetrachloride and trichloroethylene are organic solvents historically used for dissolving greasy contaminants. Sodium carbonate is an inorganic washing additive, not a dry-cleaning solvent. Many former chlorinated or aromatic dry-cleaning solvents have been restricted because of toxicity and environmental hazards.

69. Which general molecular formula represents saturated monohydric alkanols?

[AIPMT Chemistry — 2006]

(A) CₙH₂ₙO

(B) CₙH₂ₙO₂

(D) CₙH₂ₙ₊₁O

Answer: (C) CₙH₂ₙ₊₂O

Explanation: Saturated acyclic monohydric alcohols have the general formula CₙH₂ₙ₊₂O, equivalent to CₙH₂ₙ₊₁OH. Replacing a hydrogen atom of the corresponding alkane with hydroxyl leaves the total hydrogen count consistent with this expression. Methanol and ethanol are the simplest examples.

68. What type of alcohol is obtained when ethylene oxide reacts with a Grignard reagent followed by hydrolysis?

[AIPMT Chemistry — 2006]

(A) Primary alcohol

(B) Secondary alcohol

(D) Cyclopropyl alcohol

Answer: (A) Primary alcohol

Explanation: A Grignard reagent attacks the less substituted carbon of ethylene oxide, opening its three-membered epoxide ring. After protonation, the resulting product has a terminal hydroxyl group and is a primary alcohol. The process extends the Grignard carbon chain by two carbon atoms.

67. Which amine is more basic than aniline in aqueous solution?

[AIPMT Chemistry — 2006]

(A) Benzylamine

(B) Diphenylamine

(D) p-Nitroaniline

Answer: (A) Benzylamine

Explanation: In benzylamine, the nitrogen lone pair is not conjugated directly with a benzene ring, making it relatively available to accept a proton. Aniline delocalises that lone pair into its aromatic ring and is less basic. Extra phenyl or nitro substituents tend to reduce basicity.

66. Which of these organic molecules has no chiral carbon?

[AIPMT Chemistry — 2006]

(A) 2-Hydroxypropanoic acid

(B) Butan-2-ol

(D) 3-Bromopentane

Answer: (D) 3-Bromopentane

Explanation: Carbon 3 of 3-bromopentane carries bromine, hydrogen and two identical ethyl groups, so it is not stereogenic. In contrast, butan-2-ol and lactic acid each have a carbon bonded to four different groups. The dibrominated pentane can also contain stereogenic centres.

65. What is the main outcome when phenylmagnesium bromide is treated with methanol?

[AIEEE Chemistry — 2006]

(A) Anisole and magnesium hydroxide bromide

(B) Benzene and magnesium methoxide bromide

(D) Phenol and methylmagnesium bromide

Answer: (B) Benzene and magnesium methoxide bromide

Explanation: A Grignard reagent is strongly basic and reacts with the acidic hydroxyl hydrogen of methanol. Proton transfer turns the phenyl carbon into benzene and leaves a magnesium methoxide salt. Alcohols therefore destroy Grignard reagents instead of serving as inert solvents.

64. For A = formaldehyde, B = acetone, C = acetophenone and D = benzophenone, which is the increasing order of HCN addition rate?

[AIEEE Chemistry — 2006]

(A) A < B < C < D

(B) D < B < C < A

(D) C < D < B < A

Answer: (C) D < C < B < A

Explanation: Cyanide adds more readily to accessible, strongly electrophilic carbonyl carbons. Formaldehyde faces the least steric hindrance, while acetone is slower. Conjugation with phenyl rings and increasing bulk further reduce reactivity in acetophenone and particularly benzophenone.

63. Consider:
1. LNG is liquefied at extremely low temperature for storage or transport;
2. India’s first LNG terminal was at Hassan;
3. Natural-gas liquids include ethane, propane, butane and natural gasoline.

Which statements are correct?

[UPSC CSE Prelims — 2005]

(A) 1 only

(B) 1 and 3 only

(D) 1, 2 and 3

Answer: (B) 1 and 3 only

Explanation: Natural gas can be liquefied by cryogenic cooling, and hydrocarbon liquids recovered during gas processing include ethane, propane, butane and natural gasoline. India’s first operational LNG receiving terminal was at Dahej rather than Hassan. The exam therefore accepts statements one and three.

62. Bromination of 2-methylbutane in sunlight gives mainly which monobromo product?

[AIEEE Chemistry — 2005]

(A) 1-Bromo-2-methylbutane

(B) 2-Bromo-2-methylbutane

(D) 1-Bromo-3-methylbutane

Answer: (B) 2-Bromo-2-methylbutane

Explanation: Radical bromination is highly selective and favours substitution of the tertiary hydrogen in 2-methylbutane. Replacing that hydrogen yields 2-bromo-2-methylbutane as the major monobrominated product. Bromine radicals are generally much more selective than chlorine radicals in comparable substitutions.

61. Which isomer of hexane can yield only two different monochlorinated constitutional products?

[AIEEE Chemistry — 2005]

(A) n-Hexane

(B) 2,3-Dimethylbutane

(D) 2-Methylpentane

Answer: (B) 2,3-Dimethylbutane

Explanation: The highly symmetrical carbon arrangement of 2,3-dimethylbutane produces just two types of hydrogen environment: methyl and tertiary. Chlorine substitution at either type generates one constitutional monochloro derivative. The less symmetrical hexane isomers have more chemically distinct hydrogen environments.

60. Addition of one molecule of HBr to 1,3-butadiene at 40°C predominantly yields what?

[AIEEE Chemistry — 2005]

(A) 3-Bromobutene by kinetic control

(B) 1-Bromo-2-butene by thermodynamic control

(D) 1-Bromo-2-butene by kinetic control

Answer: (B) 1-Bromo-2-butene by thermodynamic control

Explanation: Conjugated 1,3-butadiene can undergo both 1,2- and 1,4-addition. At relatively higher reaction temperatures the more stable 1,4-addition product is favoured under thermodynamic control. Its position of bromine and the remaining double bond distinguish it from the kinetically favoured product.

59. Which pair consists of two types of stereoisomerism?

[AIPMT Chemistry — 2005]

(A) Structural and geometric isomerism

(B) Optical and geometric isomerism

(D) Linkage and geometric isomerism

Answer: (B) Optical and geometric isomerism

Explanation: Stereoisomers share the same connectivity but differ in the three-dimensional arrangement of atoms. Optical isomerism concerns chirality and enantiomers, while geometric isomerism involves restricted rotation or ring relationships. Chain, linkage and other structural isomerisms instead change molecular connectivity.

58. Which method was suggested for separating a mixture of naphthalene and benzoic acid?

[AIPMT Chemistry — 2005]

(A) Distillation

(B) Sublimation

(D) Crystallisation

Answer: (B) Sublimation

Explanation: Naphthalene readily sublimes and is commonly separated from less volatile residues by sublimation. Benzoic acid can also sublime under certain conditions, so quantitative separation may require controlled conditions or acid-base extraction; nevertheless, sublimation is the keyed option among the choices in the examination.

57. What is the main class of molecules making up the structural framework of cell membranes?

[AIPMT Chemistry — 2005]

(A) Neutral fats

(B) Proteins alone

(D) Carbohydrates alone

Answer: (C) Phospholipids

Explanation: Phospholipids self-assemble into a bilayer because their hydrophilic head groups face water while hydrophobic fatty-acid tails pack inward. Membrane proteins and carbohydrates also occur, but the continuous barrier is primarily a lipid bilayer formed by these amphiphilic molecules.

56. Electrolytic reduction of nitrobenzene in a weakly acidic medium yields which compound?

[AIPMT Chemistry — 2005]

(A) N-Phenylhydroxylamine

(B) Nitrosobenzene

(D) p-Aminophenol

Answer: (D) p-Aminophenol

Explanation: In weakly acidic electrolytic reduction, nitrobenzene may undergo rearrangement through intermediate stages to yield p-aminophenol. Under other reducing conditions, aniline or intermediate nitroso and hydroxylamine derivatives may predominate. The p-aminophenol outcome depends critically on the medium and electrochemical conditions.

55. Which material is a polyamide rather than a polyester, fluoropolymer or phenolic resin?

[AIEEE Chemistry — 2005]

(A) Teflon

(B) Nylon-6,6

(D) Bakelite

Answer: (B) Nylon-6,6

Explanation: Nylon-6,6 is a condensation polyamide produced from a diamine and a dicarboxylic acid. Terylene is a polyester, Teflon is polytetrafluoroethylene, and Bakelite is a crosslinked phenol-formaldehyde resin. The chemical link connecting repeating units identifies the polymer family.

54. Which of these polymers has a fully fluorinated carbon backbone?

[AIEEE Chemistry — 2005]

(A) Neoprene

(B) Teflon

(D) PVC

Answer: (B) Teflon

Explanation: Teflon is polytetrafluoroethylene, made from tetrafluoroethene units bearing fluorine on every backbone carbon. Its strong carbon-fluorine bonds give outstanding chemical stability. Neoprene contains chlorine, PVC has chlorine substituents, and Thiokol is associated with sulphur-containing elastomer networks.

53. Which oxidant best changes pent-3-en-2-ol into pent-3-en-2-one without damaging the alkene?

[AIEEE Chemistry — 2005]

(A) Acidic potassium permanganate

(B) Acidic potassium dichromate

(D) Pyridinium chlorochromate (PCC)

Answer: (D) Pyridinium chlorochromate (PCC)

Explanation: PCC is a comparatively selective oxidant for converting secondary alcohols to ketones while often preserving other sensitive groups. The substrate contains an alkene that harsher oxidising reagents might attack. The product retains its carbon–carbon double bond and gains a ketone group.

52. Acid-catalysed hydration of ordinary alkenes other than ethene usually forms which class of alcohol?

[AIEEE Chemistry — 2005]

(A) Primary alcohol only

(B) Secondary or tertiary alcohol

(D) A required mixture of secondary and tertiary alcohols

Answer: (B) Secondary or tertiary alcohol

Explanation: Acid-catalysed alkene hydration generally follows Markovnikov addition through more stable carbocation-like intermediates. Thus propene gives a secondary alcohol, while suitably branched alkenes may yield tertiary alcohols. Ethene gives ethanol, which is primary, explaining the exception stated in the question.

51. How are free radicals with unpaired electrons generally characterised?

[AIEEE Chemistry — 2005]

(A) Chemically reactive

(B) Chemically inactive

(D) Always positively charged

Answer: (A) Chemically reactive

Explanation: A free radical has at least one unpaired electron and commonly participates in chain reactions to attain more stable electron arrangements. Many radicals are short-lived and reactive, although some are resonance-stabilised. They need not carry a net positive or negative electrical charge.

50. Which of the following carboxylic acids has the smallest pKₐ?

[AIEEE Chemistry — 2005]

(A) Acetic acid

(B) Formic acid

(D) Propionic acid

Answer: (B) Formic acid

Explanation: Formic acid has no electron-releasing alkyl substituent next to its carboxyl group. Alkyl substitution usually increases electron density and slightly destabilises the carboxylate anion, decreasing acidity. Thus formic acid is stronger and has a lower pKₐ than these alkyl-substituted acids.

49. Cyclohexanone reacts with dimethylamine under acid catalysis while water is removed. What type of product forms?

[AIEEE Chemistry — 2005]

(A) Schiff base

(B) Enamine

(D) Saturated tertiary amine

Answer: (B) Enamine

Explanation: Dimethylamine is a secondary amine, so its condensation with cyclohexanone initially forms an iminium intermediate. Removal of a neighbouring proton gives a carbon–carbon double bond next to nitrogen, producing an enamine. Formation is favoured by continuously removing water.

48. Which class of medicines is chiefly used to reduce fever?

[AIEEE Chemistry — 2005]

(A) Analgesics

(B) Antipyretics

(D) Tranquilisers

Answer: (B) Antipyretics

Explanation: Antipyretics lower an elevated body temperature by acting on physiological pathways associated with fever. Certain medicines, such as paracetamol, have both antipyretic and analgesic effects. Antibiotics instead target infections, and tranquilisers treat different symptoms or conditions.

47. Which compound has the lowest boiling point?

[AIEEE Chemistry — 2004]

(A) n-Butane

(B) Isobutane

(D) 1-Butyne

Answer: (B) Isobutane

Explanation: Isobutane has a compact, branched molecular structure that generally reduces the effective surface area for London dispersion attractions relative to its straight-chain isomer. Among the four listed C₄ hydrocarbons, it therefore has the lowest normal boiling point.

46. What is the main product when HBr adds to propene in the presence of peroxide?

[AIPMT Chemistry — 2004]

(A) Isopropyl bromide

(B) 3-Bromopropane

(D) n-Propyl bromide

Answer: (D) n-Propyl bromide

Explanation: Organic peroxides promote a radical pathway for addition of hydrogen bromide to propene. Bromine adds preferentially to the terminal carbon so that the intermediate carbon radical is more stable, yielding 1-bromopropane, also called n-propyl bromide, rather than 2-bromopropane.

45. With anhydrous AlCl₃ as catalyst, which reagent combines with benzene to form ethylbenzene?

[AIPMT Chemistry — 2004]

(A) Ethanol

(B) Propene

(D) Ethane

Answer: (C) Ethene

Explanation: Benzene can undergo Friedel–Crafts alkylation with ethene under appropriate catalysed conditions, introducing an ethyl substituent. Propene would introduce a propyl-derived group, while ethane is too unreactive for this electrophilic substitution. The target hydrocarbon is ethylbenzene.

44. Which substance is an example of a chain-growth polymer?

[AIPMT Chemistry — 2004]

(A) Starch

(B) Nucleic acid

(D) Protein

Answer: (C) Polystyrene

Explanation: Polystyrene is formed by chain-growth polymerisation of styrene molecules through their carbon-carbon double bonds. Starch, proteins and nucleic acids are naturally occurring condensation-linked biopolymers. Chain growth typically involves reactive centres that successively add monomer units to a growing chain.

43. Which alcohol fails to give the yellow iodoform precipitate with iodine and alkali?

[AIPMT Chemistry — 2004]

(A) Propan-2-ol

(B) Butan-2-ol

(D) Ethanol

Answer: (C) Methanol

Explanation: The iodoform test is positive for compounds containing or oxidisable to a methyl ketone group, including ethanol and secondary alcohols of the CH₃CH(OH)R type. Methanol does not have this structural feature and fails to produce yellow iodoform crystals.

42. Which reagent can replace the –OH group of an alcohol or –COOH group of a carboxylic acid by chlorine?

[AIPMT Chemistry — 2004]

(A) Phosphorus pentachloride

(B) Hypochlorous acid

(D) Hydrochloric acid

Answer: (A) Phosphorus pentachloride

Explanation: Phosphorus pentachloride converts many alcohols to alkyl chlorides and carboxylic acids to acyl chlorides by replacing oxygen-containing functional groups. This substitution chemistry is characteristic of phosphorus chlorinating reagents. Direct chlorine gas or dilute hydrochloric acid is not the general reagent described.

41. Which compound can be oxidised to a corresponding carbonyl compound?

[AIPMT Chemistry — 2004]

(A) Propan-2-ol

(B) o-Nitrophenol

(D) 2-Methylpropan-2-ol

Answer: (A) Propan-2-ol

Explanation: Propan-2-ol is a secondary alcohol and oxidises to propanone, a ketone bearing a carbonyl group. Tertiary alcohols lack the hydrogen required at the carbinol carbon for ordinary oxidation, while phenols typically undergo different oxidation chemistry. Hence propan-2-ol fits the question.

40. What is the principal function of haemoglobin as a protein?

[AIPMT Chemistry — 2004]

(A) Catalysing every biological reaction

(B) Maintaining blood sugar concentration

(D) Forming antibodies against infections

Answer: (C) Transporting oxygen in blood

Explanation: Haemoglobin is the oxygen-binding protein of red blood cells. Its haem groups contain iron that reversibly binds oxygen in the lungs and releases it to tissues. Antibodies, metabolic enzymes and blood-glucose-regulating hormones are other proteins with different structures and functions.

39. Which interactions mainly stabilise the alpha-helical secondary structure of proteins?

[AIPMT Chemistry — 2004]

(A) Dipeptide bonds

(B) Hydrogen bonds

(D) Peptide bonds alone

Answer: (B) Hydrogen bonds

Explanation: The protein alpha helix is stabilised by hydrogen bonds between backbone carbonyl oxygen atoms and amide hydrogens of residues further along the chain. Peptide bonds create the underlying sequence, but regular backbone hydrogen bonding provides much of the helix’s secondary-structure stability.

38. How many chiral carbon atoms does cyclic beta-D-(+)-glucose contain?

[AIPMT Chemistry — 2004]

(A) Five

(B) Six

(D) Four

Answer: (A) Five

Explanation: Cyclisation of D-glucose produces a new chiral centre at the anomeric carbon, C1. Together with the four original asymmetric centres at C2 to C5, the cyclic glucose molecule has five stereogenic carbon atoms. The exocyclic CH₂OH carbon is not stereogenic.

37. How many nucleotides of messenger RNA together form one amino-acid codon?

[AIPMT Chemistry — 2004]

(A) Three

(B) Four

(D) Two

Answer: (A) Three

Explanation: A codon consists of three consecutive RNA nucleotides, each bearing one of the four bases adenine, uracil, guanine or cytosine. Triplet combinations provide 64 codons, which specify amino acids or translation stops. This underlies the genetic code used during protein synthesis.

36. Which hormone favours the conversion of blood glucose into stored glycogen?

[AIPMT Chemistry — 2004]

(A) Cortisone

(B) Bile acids

(D) Insulin

Answer: (D) Insulin

Explanation: Insulin encourages uptake of glucose by suitable cells and stimulates glycogen synthesis, particularly in liver and muscle. Glycogen is a branched polymer of glucose used for energy storage. Adrenaline more commonly promotes glycogen breakdown to make glucose available rapidly.

35. Which organic cationic surfactant produces positively charged micelles?

[AIPMT Chemistry — 2004]

(A) Sodium dodecyl sulphate

(B) Sodium acetate

(D) Cetyltrimethylammonium bromide

Answer: (D) Cetyltrimethylammonium bromide

Explanation: Cetyltrimethylammonium bromide contains a positively charged quaternary ammonium head and a long hydrocarbon tail. Above its critical micelle concentration, its molecules aggregate into micelles with cationic surfaces. Sodium dodecyl sulphate instead forms negatively charged micelles.

34. Which substrate reacts least readily in an ordinary nucleophilic substitution?

[AIPMT Chemistry — 2004]

(A) tert-Butyl chloride

(B) Vinyl chloride (CH₂=CHCl)

(D) Allyl chloride

Answer: (B) Vinyl chloride (CH₂=CHCl)

Explanation: In vinyl chloride the carbon bearing chlorine has sp² hybridisation, creating a strong carbon–chlorine bond. It resists conventional SN1 carbocation formation and SN2 backside attack. Allylic halides are comparatively reactive, while ordinary primary or tertiary halides can react through suitable mechanisms.

33. Excess methylmagnesium iodide reacts with acetyl bromide; after aqueous work-up, which product predominates?

[AIEEE Chemistry — 2004]

(A) Acetone

(B) Acetyl iodide

(D) Acetamide

Answer: (C) 2-Methylpropan-2-ol

Explanation: An acyl halide first reacts with a Grignard reagent to give a ketone intermediate, which reacts with a second equivalent to yield a tertiary alcohol after work-up. With an acetyl group and methylmagnesium iodide, the resulting alcohol is tert-butanol.

32. Arrange the acidity of benzoic acid (a), o-nitrobenzoic acid (b), p-nitrobenzoic acid (c), and m-nitrobenzoic acid (d).

[AIEEE Chemistry — 2004]

(A) b > d > a > c

(B) b > d > c > a

(D) b > c > d > a

Answer: (D) b > c > d > a

Explanation: The nitro group withdraws electrons and stabilises the carboxylate conjugate base. The ortho isomer benefits from the pronounced ortho effect; para substitution allows both resonance and inductive withdrawal, whereas meta substitution operates mainly inductively. Unsubstituted benzoic acid is least acidic.

31. Which compound can exist as a meso stereoisomer?

[AIEEE Chemistry — 2004]

(A) 2-Chlorobutane

(B) 2-Hydroxypropanoic acid

(D) 2,3-Dichlorobutane

Answer: (D) 2,3-Dichlorobutane

Explanation: 2,3-Dichlorobutane possesses two stereogenic centres and a symmetric carbon framework. One configuration contains an internal plane of symmetry and is consequently optically inactive despite the chiral centres. The other listed compounds lack the required internal symmetry for this meso form.

30. Which compound contains no sp²-hybridised carbon atom?

[AIEEE Chemistry — 2004]

(A) Acetone

(B) Acetamide

(D) Acetic acid

Answer: (C) Acetonitrile

Explanation: In acetonitrile, CH₃C≡N, the nitrile carbon is sp-hybridised and the methyl carbon is sp³-hybridised. Acetone, acetamide and acetic acid each contain a carbonyl carbon, which is normally trigonal planar and sp²-hybridised.

29. Which of these compounds is not chiral?

[AIEEE Chemistry — 2004]

(A) 1-Chloropentane

(B) 3-Chloro-2-methylpentane

(D) 2-Chloropentane

Answer: (A) 1-Chloropentane

Explanation: 1-Chloropentane has no carbon attached to four different substituents and is therefore achiral. Each of the other named molecules contains at least one stereogenic carbon under the indicated structure. Chirality here depends on substituent differences, not merely the presence of chlorine.

28. What happens when ethyl acetate is mixed with an ordinary aqueous sodium chloride solution?

[AIEEE Chemistry — 2004]

(A) Ethyl acetate and sodium chloride remain chemically unchanged

(B) Chloromethane and sodium propanoate form

(D) Sodium acetate and ethanol form immediately

Answer: (A) Ethyl acetate and sodium chloride remain chemically unchanged

Explanation: Ordinary aqueous sodium chloride does not provide the strong acid or base required to hydrolyse ethyl acetate rapidly. The ester therefore remains chemically unchanged; dissolved salt can instead reduce its solubility in the water layer through a salting-out effect.

27. Which listed carbonyl compound undergoes the Cannizzaro reaction in concentrated alkali?

[AIEEE Chemistry — 2004]

(A) Phenol

(B) Benzoic acid

(D) Benzaldehyde

Answer: (D) Benzaldehyde

Explanation: Benzaldehyde has no alpha hydrogen and can undergo Cannizzaro disproportionation in concentrated hydroxide solution. One aldehyde molecule is oxidised to a benzoate ion as another is reduced to benzyl alcohol. Butanal possesses alpha hydrogen and generally favours aldol chemistry.

26. Which organic compound can be reduced to its corresponding hydrocarbon by the Clemmensen method?

[AIEEE Chemistry — 2004]

(A) Ethyl acetate

(B) Butan-2-one

(D) Acetic acid

Answer: (B) Butan-2-one

Explanation: Clemmensen reduction converts an aldehyde or ketone carbonyl into a methylene group using zinc amalgam and strong hydrochloric acid. Butan-2-one is therefore converted into butane. Esters, amides and carboxylic acids do not ordinarily undergo the same direct transformation.

25. Why are sodium sulphate and sodium silicate added to detergent washing powder?
1. To keep it dry;
2. To maintain alkalinity.

[UPSC CSE Prelims — 2003]

(A) Only statement 1

(B) Only statement 2

(D) Neither statement 1 nor 2

Answer: (C) Both statements 1 and 2

Explanation: Sodium sulphate acts as a bulking and flow-supporting ingredient in washing powders, helping the mixture remain dry and manageable. Sodium silicate contributes alkalinity and detergent-building properties. Both functions support the performance and storage stability of detergent formulations, making both statements correct.

24. Which alkane produces just one monochloro derivative on UV-initiated chlorination?

[AIEEE Chemistry — 2003]

(A) n-Pentane

(B) Isopentane

(D) Propane

Answer: (C) Neopentane

Explanation: All twelve hydrogen atoms of neopentane occupy equivalent methyl positions because of its highly symmetrical structure. Substituting any one of them with chlorine gives the same constitutional product. The other listed alkanes have nonequivalent hydrogens and produce more than one monochloro isomer.

23. By which reagent can 1-butene be converted into butane?

[AIEEE Chemistry — 2003]

(A) Sn/HCl

(B) Zn-Hg

(D) Zn/HCl

Answer: (C) H₂/Pd

Explanation: Catalytic hydrogenation adds molecular hydrogen across the carbon-carbon double bond of but-1-ene. Palladium facilitates formation of the saturated alkane butane. The other reagent systems commonly serve reduction purposes but do not represent the usual catalytic hydrogenation of an isolated alkene.

22. What is the reactivity order of aniline
(I), benzene
(II) and nitrobenzene
(III) towards electrophilic aromatic substitution?

[AIPMT Chemistry — 2003]

(A) III > II > I

(B) II > III > I

(D) I > II > III

Answer: (D) I > II > III

Explanation: Aniline’s amino group donates electron density to the aromatic ring by resonance, activating it toward electrophilic substitution. Nitrobenzene is strongly deactivated by its electron-withdrawing nitro group, while benzene is intermediate. Accordingly, the reactivity order is aniline, benzene and then nitrobenzene.

21. Formation of lactic acid by cyanohydrin addition to ethanal and hydrolysis yields which optical composition?

[AIPMT Chemistry — 2003]

(A) Pure D-isomer

(B) Pure L-isomer

(D) 20% D and 80% L

Answer: (C) Equal D and L isomers

Explanation: The planar carbonyl carbon of ethanal can be attacked by cyanide from either face with equal probability when no chiral influence is present. Hydrolysis then yields a racemic lactic acid mixture containing equal amounts of the two enantiomers, designated D and L.

20. Which order correctly arranges the acid strengths of carboxylic acid, water, alcohol and acetylene?

[AIPMT Chemistry — 2003]

(A) RCOOH > ROH > H₂O > HC≡CH

(B) RCOOH > H₂O > ROH > HC≡CH

(D) RCOOH > HC≡CH > H₂O > ROH

Answer: (B) RCOOH > H₂O > ROH > HC≡CH

Explanation: Typical carboxylic acids have pKa values near 4–5, water about 15.7, simple alcohols about 16–18 and ethyne approximately 25. Lower pKa corresponds to greater acidity. This yields carboxylic acid stronger than water, followed by alcohol and then acetylene.

19. Phospholipids are esters of glycerol with which groups?

[AIPMT Chemistry — 2003]

(A) Three fatty-acid groups

(B) Two fatty-acid groups and a phosphate group

(D) Three phosphate groups

Answer: (B) Two fatty-acid groups and a phosphate group

Explanation: A typical glycerophospholipid contains a glycerol backbone esterified to two fatty acid chains and connected to a phosphate-containing head. Its water-loving head and water-repelling tails drive lipid bilayer formation. Such compounds are major structural components of cellular membranes.

18. According to Chargaff’s rule, what equality applies to the bases of double-stranded DNA?

[AIPMT Chemistry — 2003]

(A) A = T and G = C

(B) A = G and T = C

(D) All four bases have equal amounts

Answer: (A) A = T and G = C

Explanation: In ordinary double-stranded DNA, adenine pairs with thymine, while guanine pairs with cytosine. This complementary pairing means the number of A bases equals T and the number of G bases equals C. It does not require all four bases to be equally abundant.

17. Which metallic ion is present in the molecular structure of vitamin B12?

[AIPMT Chemistry — 2003]

(A) Iron(II)

(B) Cobalt(III)

(D) Calcium(II)

Answer: (B) Cobalt(III)

Explanation: Vitamin B12 is also known as cobalamin because its complex molecular structure contains a cobalt centre coordinated within a corrin ring. Cobalt is essential to this vitamin’s biochemical actions. Iron occurs in haemoproteins instead, while zinc and calcium have unrelated biological functions.

16. What chemical transformation is called glycolysis?

[AIPMT Chemistry — 2003]

(A) Oxidation of glucose to glutamate

(B) Conversion of pyruvate to citrate

(D) Conversion of glucose into haem

Answer: (C) Breakdown of glucose into pyruvate

Explanation: Glycolysis is a sequence of enzyme-catalysed reactions that breaks one glucose molecule into two pyruvate molecules. Energy from this pathway is conserved as ATP and NADH. It is a central metabolic route and can proceed even without oxygen in many cells.

15. Nylon threads are made from which class of synthetic polymers?

[AIEEE Chemistry — 2003]

(A) Polyesters

(B) Polyamides

(D) Polyvinyl compounds

Answer: (B) Polyamides

Explanation: Nylon contains repeating amide bonds in its backbone and therefore belongs to the polyamide family. Strong hydrogen bonding among adjacent chains gives nylon fibre durability and tensile strength. Polyester and polyvinyl materials differ in their fundamental chemical linkages and preparation.

14. What is the first step in sulphuric-acid-catalysed dehydration of an alcohol?

[AIEEE Chemistry — 2003]

(A) Direct carbocation formation

(B) Loss of water before any protonation

(D) Protonation of the alcohol oxygen

Answer: (D) Protonation of the alcohol oxygen

Explanation: Strong acid initially protonates the hydroxyl oxygen, converting the poor leaving group OH into a better leaving group, water. Subsequent steps may include loss of water and beta-hydrogen elimination. The mechanism and ease of dehydration depend on whether the alcohol is primary, secondary or tertiary.

13. Why is an ether often more volatile than an isomeric alcohol?

[AIEEE Chemistry — 2003]

(A) Alcohols uniquely have resonance

(B) Ethers form strong intermolecular hydrogen bonds with themselves

(D) Only ethers possess a molecular dipole

Answer: (C) Alcohols form intermolecular hydrogen bonds with themselves

Explanation: Alcohol molecules form hydrogen bonds through their hydroxyl groups, which increase intermolecular attraction and elevate boiling points. Ethers have an oxygen lone pair but no O–H bond, so they cannot donate comparable hydrogen bonds to one another. They therefore often evaporate more readily.

12. What is the correct IUPAC name for CH₃COCH(CH₃)₂?

[AIEEE Chemistry — 2003]

(A) 2-Methylbutan-3-one

(B) 4-Methylisopropyl-1-ketone

(D) Isopropylmethyl ketone

Answer: (C) 3-Methylbutan-2-one

Explanation: The longest carbon chain containing the ketone group has four carbon atoms. Numbering from the carbonyl end places the carbonyl carbon at position two and a methyl branch at position three. Hence the systematic name is 3-methylbutan-2-one.

11. Why are the two C–O bonds of the formate ion, HCOO⁻, equal in length?

[AIEEE Chemistry — 2003]

(A) The C=O bond is weaker than a C–O bond

(B) The ion has two equivalent resonance structures

(D) Carbon has hybridised orbitals

Answer: (B) The ion has two equivalent resonance structures

Explanation: Formate is a resonance hybrid of two equivalent contributing structures, each placing the negative charge on a different oxygen atom. Neither carbon–oxygen bond is exclusively single or double; both therefore have the same intermediate bond order and essentially equal lengths.

10. The formula CₙH₂ₙO₂ can describe which homologous series of saturated open-chain monofunctional compounds?

[AIEEE Chemistry — 2003]

(A) Monocarboxylic acids

(B) Diols

(D) Diketones

Answer: (A) Monocarboxylic acids

Explanation: A saturated acyclic monocarboxylic acid has one carboxyl group and follows the formula CₙH₂ₙO₂. Ethanoic acid, C₂H₄O₂, is an example. Saturated diols normally contain more hydrogen, while dialdehydes and diketones have different degrees of unsaturation.

9. What is the principal product of reducing CH₂=CHCOOH with LiAlH₄ followed by hydrolysis?

[AIEEE Chemistry — 2003]

(A) CH₂=CHCH₂OH

(B) CH₃CH₂CH₂OH

(D) CH₃CH₂COOH

Answer: (A) CH₂=CHCH₂OH

Explanation: Lithium aluminium hydride converts the carboxylic acid group of acrylic acid into a primary alcohol. Under the normal conditions of this reaction, the carbon–carbon double bond remains intact. The product is allyl alcohol, CH₂=CHCH₂OH, rather than saturated propanol.

8. Which reagent does not ordinarily react with acetylene?

[AIEEE Chemistry — 2002]

(A) Sodium hydroxide

(B) Ammoniacal silver nitrate

(D) Hydrochloric acid

Answer: (A) Sodium hydroxide

Explanation: Ethyne has weakly acidic terminal hydrogens and forms acetylides with suitable reagents such as reactive metals or ammoniacal silver salts. Hydrochloric acid can add across its triple bond under suitable conditions. Sodium hydroxide is too weak a base to deprotonate ethyne appreciably.

7. What organic product forms when acetylene reacts with hypochlorous acid?

[AIEEE Chemistry — 2002]

(A) Acetyl chloride (CH₃COCl)

(B) Chloroacetaldehyde (ClCH₂CHO)

(D) Chloroacetic acid (ClCH₂COOH)

Answer: (B) Chloroacetaldehyde (ClCH₂CHO)

Explanation: Hypochlorous acid adds across the carbon-carbon triple bond of acetylene and an initially formed enol rearranges to a carbonyl compound. The product is chloroacetaldehyde, containing one chlorine atom and an aldehyde group. This is a classic electrophilic addition followed by tautomerisation.

6. Cellulose is a polymer of which sugar?

[AIPMT Chemistry — 2002]

(A) Glucose

(B) Fructose

(D) Sucrose

Answer: (A) Glucose

Explanation: Cellulose is a natural polysaccharide formed by repeating beta-D-glucose units linked by beta-1,4 glycosidic bonds. Its extended hydrogen-bonded chains create strong plant cell-wall fibres. Fructose, ribose and sucrose are sugars but do not form cellulose’s repeating structural building block.

5. Phenol treated with chloroform and sodium hydroxide mainly forms what?

[AIPMT Chemistry — 2002]

(A) Benzaldehyde

(B) Salicylaldehyde

(D) Benzoic acid

Answer: (B) Salicylaldehyde

Explanation: The Reimer–Tiemann reaction introduces a formyl group predominantly at the ortho position of phenol. Chloroform in base generates an electrophilic species that reacts with the phenoxide-activated aromatic ring. Subsequent hydrolysis yields salicylaldehyde, also known as 2-hydroxybenzaldehyde.

4. Which process can distinguish n-propyl alcohol from isopropyl alcohol?

[AIPMT Chemistry — 2002]

(A) Treatment with phosphorus pentachloride

(B) Reduction

(D) Ozonolysis

Answer: (C) Oxidation using potassium dichromate

Explanation: n-Propyl alcohol is a primary alcohol and can be oxidised to propanal and propanoic acid. Isopropyl alcohol is secondary and oxidises to propanone. Examining the different oxidation products therefore distinguishes the two positional alcohol isomers more reliably than the other specified operations.

3. Enzymes generally consist of which type of substance?

[AIPMT Chemistry — 2002]

(A) Edible proteins irrespective of structure

(B) Proteins possessing a particular three-dimensional structure

(D) Carbohydrates alone

Answer: (B) Proteins possessing a particular three-dimensional structure

Explanation: Most enzymes are proteins whose specific folded three-dimensional structures enable catalytic activity. The shape of an active site helps recognise substrates and lower the activation energy of biochemical reactions. Their function depends on chemical composition and structure rather than merely whether a protein is edible.

2. Which sequence gives the correct relative ease of dehydrohalogenation among alkyl halides R–X?

[AIPMT Chemistry — 2002]

(A) R–F > R–Cl > R–Br > R–I

(B) R–I > R–Br > R–Cl > R–F

(D) R–F > R–I > R–Br > R–Cl

Answer: (B) R–I > R–Br > R–Cl > R–F

Explanation: Under comparable elimination conditions, iodide is usually the best leaving group and fluoride the poorest. The ease of breaking the carbon–halogen bond and stabilising the departing halide generally follows iodide, bromide, chloride and fluoride. Substrate structure and mechanism can modify detailed rates.

1. What feature do optical isomerism and geometrical isomerism have in common?

[AIEEE Chemistry — 2002]

(A) Both always give the same number of isomers

(B) One type necessarily implies the other

(D) They share no stereochemical feature

Answer: (C) Both are forms of stereoisomerism

Explanation: Optical isomers and geometrical isomers differ in three-dimensional molecular arrangement without changing atom connectivity. Both therefore belong to stereoisomerism. Optical isomerism commonly involves non-superimposable mirror-image forms, whereas geometric isomerism arises from restricted rotation or ring arrangements.

280. Unsaturated hydrocarbons usually produce:

279. Which property of carbon allows it to form a large number of compounds by bonding with itself and other elements?

278. Baking soda releases which gas on heating?

277. Which of the following is a straight-chain saturated hydrocarbon?

276. A molecule of methane contains one carbon atom bonded to four hydrogen atoms. What is the chemical formula for methane?

275. Statement A: Carboxylic acids are strong acids that completely ionise in water. Statement B: Ethanoic acid is a weak acid compared to hydrochloric acid. Select the correct option.

274. Which of the following is a ring-chain hydrocarbon?

273. What are the primary products formed during the complete combustion of most carbon compounds?

272. Which of the following is an example of a cyclic hydrocarbon?

271. Which of the following is true about the homologous series?

270. What is typically involved in an addition reaction?

269. Ethanoic acid reacts with ethanol in the presence of concentrated H₂SO₄ to form:

268. What is formed when ethanol is oxidised using an oxidising agent like alkaline KMnO₄?

267. Which of the following is a homologous series?

266. Carbon has the unique ability to form bonds with other carbon atoms, giving rise to large molecules. This property is called:

265. What is the primary characteristic that defines organic compounds?

264. The reaction of an alcohol with ethanoic acid in the presence of a catalyst forms water and:

263. Statement A: Alcohols react with sodium to evolve hydrogen. Statement B: No gas is evolved when sodium reacts with ethanol. Choose the correct statement.

262. Which alcohol is commonly used as fuel?

261. Select the example of a functional group that does not contain a double bond in its structure.

260. Esters are __________ substances.

259. What type of gas is released when ethanol reacts with sodium?

258. Which structural feature contributes to the high reactivity of unsaturated organic compounds?

257. Which of the following hydrocarbons contains a branched chain?

256. Which of the following represents a straight-chain hydrocarbon?

255. Why does carbon form covalent bonds in organic compounds?

254. Which of the following is a saturated hydrocarbon?

253. What is the primary role of a functional group in an organic compound?

252. Which of the following compounds is a saturated hydrocarbon?

251. Which of the following is an organic compound?

250. Which of the following has a branched-chain hydrocarbon?

249. Which property of carbon permits one carbon atom to bond with other carbon atoms?

248. An organic compound always contains which of the following?

247. What type of bonding exists in most organic compounds?

246. What is the IUPAC name of an organic compound having two carbon atoms and a hydroxyl (–OH) group?

245. Detergents can work in which of the following?

244. Which of the following products is formed on complete combustion of hydrocarbons?

243. Which compound is classified as a saturated hydrocarbon?

242. Which structural formula represents the branched-chain compound neopentane?

241. When a hydrocarbon is burnt in excess air, the final products are:

240. Which of the following is NOT considered an organic compound?

239. Which of the following has a straight-chain hydrocarbon?

238. Which of these organic compounds is saturated?

237. Match each polymer to its monomer unit: (i) Glyptal, (ii) Bakelite, (iii) Nylon-2-nylon-6, (iv) Buna-N. (A) Glycine + aminocaproic acid, (B) Phenol + formaldehyde, (C) Butadiene + acrylonitrile, (D) Ethylene glycol + phthalic acid.

236. What is the full form of PETN, an explosive referred to in tunnelling applications?

235. The most powerful explosive used in blasting among the following is:

234. Which of the following is an example of a synthetic polymer used in industry?

233. Which resilient polymer is used in industrial brushes and toothbrush bristles?

232. DNA is a polymer of deoxyribonucleotides. Which structural feature does this describe?

231. Amylopectin consists mainly of glucose units joined along its chains by which bonds?

230. Biogas plants are most commonly used in which sector in rural India?

229. What fuel combination was announced for ISRO’s Next Generation Launch Vehicle engine?

228. How many additional million tonnes of FCI rice were allocated for ethanol production in May 2025?

227. Which initiative supports compressed biogas plants supplying automotive and industrial fuels to oil marketing companies?

226. Which engine under development for ISRO’s LVM3 uses a kerosene-based fuel system?

225. What is the defining characteristic of an unsaturated carbon compound?

224. Which of the following compounds is unsaturated?

223. Which carbon properties together explain the huge diversity of organic compounds?

222. Which of the following are building blocks of proteins?

221. What is denatured alcohol?

220. What is the chemical name of the compound responsible for the cooling sensation in mint leaves?

219. What is the primary acid found in citrus fruits such as oranges and lemons?

218. Which organism is used in the bread and alcohol industries?

217. Which gas is released when vinegar and baking soda are combined, inflating a balloon?

216. Which reaction forms glucose pentaacetate when glucose reacts with acetic anhydride?

215. What does RDX stand for, according to the given options?

214. What is the full form of TNT?

213. What is the molecular formula of the first member of the alkene series?

212. In which Madhya Pradesh district is a polymer-manufacturing factory located?

211. Which of the following is not a natural fibre?

210. Trinitrotoluene is used for which purpose?

209. Which compound–melting point pair is correct? I. Acetic acid—290 K. II. Ethanol—156 K.

208. Which class of organic compounds contains the –OH functional group?

207. What is the approximate proportion of methane in cow-dung biogas?

206. Which of these tranquilising medicines is a barbiturate?

205. Complete the anaerobic respiration reaction: Glucose → ______ + carbon dioxide + energy.

204. Which of the following compounds contains only one carbon–carbon single bond?

203. The general formula CnH2n−2 represents:

202. Why do typical carbon compounds not conduct electricity in the molten state?

201. Carbon compounds linked by only single carbon–carbon bonds are known as:

275. Statement A: Carboxylic acids are strong acids that completely ionise in water.
Statement B: Ethanoic acid is a weak acid compared to hydrochloric acid.

Select the correct option.

263. Statement A: Alcohols react with sodium to evolve hydrogen.
Statement B: No gas is evolved when sodium reacts with ethanol.

Choose the correct statement.

237. Match each polymer to its monomer unit:
(i) Glyptal,
(ii) Bakelite,
(iii) Nylon-2-nylon-6,
(iv) Buna-N.

(A) Glycine + aminocaproic acid,
(B) Phenol + formaldehyde,
(C) Butadiene + acrylonitrile,
(D) Ethylene glycol + phthalic acid.

209. Which compound–melting point pair is correct?
I. Acetic acid—290 K.
II. Ethanol—156 K.

185. Statement I: Most carbon compounds are good conductors of electricity.
Statement II: Intermolecular forces in many molecular carbon compounds are not very strong.

Choose the correct answer.

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?

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.

173. Evaluate:
I. Aspirin and paracetamol are narcotic analgesics.
II. Morphine and heroin are non-narcotic analgesics.

170. Which feedstocks qualify under India’s National Policy on Biofuels:
1 Cassava,
2 damaged wheat,
3 groundnut,
4 horse gram,
5 rotten potatoes,
6 sugar beet?

160. Regarding the Petroleum and Natural Gas Regulatory Board:
1. It was India’s first regulatory body.
2. It seeks competitive gas markets.
3. Appeals go to the electricity appellate tribunal.

Which are correct?

148. With reference to algae biofuels:
1. Production is possible only in seas.
2. High technical expertise is needed.
3. Large installations can raise ecological concerns.

Which statements are correct?

147. Regarding the Climate and Clean Air Coalition:
1. It is a G20-only initiative.
2. It targets methane, black carbon and hydrofluorocarbons.

Which is correct?

144. Which statements about vinegar are correct?
A. Sugarcane juice can be fermented to make vinegar.
B. Vinegar contains acetic acid.
C. Its characteristic acid is benzoic acid.
D. It preserves food.