1. Hydrocarbons are compounds made up of:
a) Carbon and oxygen
b) Carbon and hydrogen
c) Carbon and nitrogen
d) Carbon and sulphur
Answer: b) Carbon and hydrogen
Explanation: Hydrocarbons are organic compounds consisting only of carbon and hydrogen atoms.
2. The simplest hydrocarbon is:
a) Methane
b) Ethane
c) Propane
d) Acetylene
Answer: a) Methane
Explanation: Methane (CH₄) is the first member of alkanes.
3. Alkanes are also called:
a) Olefins
b) Paraffins
c) Aromatics
d) Acetylenes
Answer: b) Paraffins
Explanation: Alkanes are saturated hydrocarbons (CnH₂n+2), also called paraffins (little reactivity).
4. General formula of alkanes is:
a) CnH₂n
b) CnH₂n+2
c) CnH₂n–2
d) CnH₂n+1
Answer: b) CnH₂n+2
Explanation: Alkanes follow general formula CnH₂n+2.
5. Ethane (C₂H₆) belongs to:
a) Alkanes
b) Alkenes
c) Alkynes
d) Aromatics
Answer: a) Alkanes
Explanation: Ethane is a saturated hydrocarbon with single bonds only.
6. Which alkane has 3 carbon atoms?
a) Methane
b) Ethane
c) Propane
d) Butane
Answer: c) Propane
Explanation: Propane (C₃H₈) is the third member of alkanes.
7. Butane is used in:
a) Fertilizer industry
b) LPG as cooking fuel
c) Explosives
d) Plastics
Answer: b) LPG as cooking fuel
Explanation: LPG is mainly a mixture of propane and butane.
8. Isomerism starts from which alkane?
a) Methane
b) Ethane
c) Propane
d) Butane
Answer: d) Butane
Explanation: Butane (C₄H₁₀) has two isomers – n-butane and isobutane.
9. Cycloalkanes have general formula:
a) CnH₂n+2
b) CnH₂n
c) CnH₂n–2
d) CnH₂n+1
Answer: b) CnH₂n
Explanation: Cycloalkanes are ring hydrocarbons with general formula CnH₂n.
10. The IUPAC name of isobutane is:
a) 2-methylpropane
b) 2-methylbutane
c) 3-methylpentane
d) 2,2-dimethylpropane
Answer: a) 2-methylpropane
Explanation: Isobutane is a branched-chain isomer of butane.
11. Alkanes are generally obtained from:
a) Natural gas and petroleum
b) Coal
c) Air
d) Plants only
Answer: a) Natural gas and petroleum
Explanation: Natural gas contains methane, ethane, propane, and butane.
12. The main constituent of natural gas is:
a) Ethane
b) Methane
c) Propane
d) Butane
Answer: b) Methane
Explanation: Natural gas has ~80–90% methane.
13. Which alkane is also known as marsh gas?
a) Ethane
b) Propane
c) Methane
d) Butane
Answer: c) Methane
Explanation: Methane forms in marshes by decomposition of organic matter.
14. Which alkane is used as a refrigerant in the form of liquefied gas?
a) Methane
b) Ethane
c) Propane
d) Butane
Answer: c) Propane
Explanation: Propane is used in refrigeration and air-conditioning systems.
15. Combustion of alkanes produces:
a) CO only
b) CO₂ + H₂O
c) H₂ only
d) CO₂ + N₂
Answer: b) CO₂ + H₂O
Explanation: Complete combustion of alkanes → carbon dioxide + water.
16. Incomplete combustion of alkanes produces:
a) Only CO₂
b) Carbon monoxide and soot
c) Methanol
d) Oxygen
Answer: b) Carbon monoxide and soot
Explanation: Limited oxygen supply → CO + C (soot).
17. The reaction of alkanes with chlorine in presence of sunlight is called:
a) Addition reaction
b) Substitution reaction
c) Oxidation reaction
d) Hydrogenation
Answer: b) Substitution reaction
Explanation: Alkanes undergo free radical substitution with halogens.
18. The main reaction of alkanes is:
a) Addition
b) Substitution
c) Polymerization
d) Oxidation
Answer: b) Substitution
Explanation: Alkanes are saturated → undergo substitution.
19. Pyrolysis of alkanes is:
a) Heating in presence of oxygen
b) Heating in absence of air
c) Reaction with halogens
d) Oxidation
Answer: b) Heating in absence of air
Explanation: Pyrolysis = thermal decomposition → smaller alkanes + alkenes.
20. The process of converting alkanes into aromatic hydrocarbons is:
a) Hydrogenation
b) Aromatization
c) Isomerization
d) Substitution
Answer: b) Aromatization
Explanation: Aromatization converts alkanes into benzene/toluene (catalysts used).
21. The octane number of a fuel indicates:
a) Density
b) Antiknocking property
c) Calorific value
d) Cost
Answer: b) Antiknocking property
Explanation: Higher octane number = better fuel efficiency.
22. Iso-octane is used as:
a) Reference fuel in octane number scale
b) Solvent
c) Explosive
d) Refrigerant
Answer: a) Reference fuel in octane number scale
Explanation: Iso-octane = 100 octane rating, reference standard.
23. Knocking in petrol engines is reduced by adding:
a) Lead tetraethyl
b) Alcohol
c) Acetone
d) Hydrogen
Answer: a) Lead tetraethyl
Explanation: Lead tetraethyl (historically) improved octane rating.
24. Which alkane is used in the production of carbon black?
a) Methane
b) Ethane
c) Acetylene
d) Natural gas
Answer: d) Natural gas
Explanation: Methane-rich natural gas is burnt in limited oxygen → carbon black (tyres, inks).
25. Higher alkanes are generally found in:
a) Natural gas
b) Kerosene and diesel fractions of petroleum
c) Coal gas
d) Air
Answer: b) Kerosene and diesel fractions of petroleum
Explanation: Higher alkanes (C₁₀–C₁₆) are in kerosene, diesel, and lubricating oils.
26. Alkenes are also called:
a) Paraffins
b) Olefins
c) Aromatics
d) Acetylenes
Answer: b) Olefins
Explanation: Alkenes (CnH₂n) are unsaturated hydrocarbons with double bonds, called olefins.
27. General formula of alkenes is:
a) CnH₂n+2
b) CnH₂n
c) CnH₂n–2
d) CnH₂n–1
Answer: b) CnH₂n
Explanation: Alkenes have one double bond, general formula CnH₂n.
28. The first member of alkenes is:
a) Methene
b) Ethene
c) Propene
d) Butene
Answer: b) Ethene
Explanation: Ethene (C₂H₄) is the simplest alkene.
29. The IUPAC name of propylene is:
a) But-1-ene
b) Ethene
c) Prop-1-ene
d) But-2-ene
Answer: c) Prop-1-ene
Explanation: Propylene is prop-1-ene (CH₂=CH–CH₃).
30. Alkenes mainly undergo:
a) Substitution reactions
b) Addition reactions
c) Elimination reactions
d) Oxidation reactions only
Answer: b) Addition reactions
Explanation: Double bonds make alkenes reactive towards electrophilic addition.
31. Which of the following is an addition reaction of ethene?
a) Ethene + H₂ → Ethane
b) Ethene + Cl₂ → Dichloroethane
c) Ethene + HCl → Chloroethane
d) All of the above
Answer: d) All of the above
Explanation: Alkenes undergo hydrogenation and halogenation addition reactions.
32. The addition of HCl to alkenes follows:
a) Markovnikov’s rule
b) Hund’s rule
c) Le Chatelier’s principle
d) Pauli’s rule
Answer: a) Markovnikov’s rule
Explanation: According to Markovnikov’s rule, H attaches to carbon with more hydrogens.
33. Anti-Markovnikov addition occurs in the presence of:
a) Peroxides
b) Acids
c) Alkali metals
d) Bases
Answer: a) Peroxides
Explanation: With peroxides, HBr adds to alkenes in anti-Markovnikov fashion.
34. Ethene is used in:
a) Welding
b) Ripening of fruits
c) Rocket fuel
d) Anaesthesia
Answer: b) Ripening of fruits
Explanation: Ethene is a plant hormone that induces fruit ripening.
35. Which reagent is used to test unsaturation in hydrocarbons?
a) Bromine water
b) Acidified KMnO₄
c) Baeyer’s reagent
d) All of these
Answer: d) All of these
Explanation: Bromine water and Baeyer’s reagent (KMnO₄) decolorize with alkenes/alkynes.
36. Alkenes on oxidation with cold dilute KMnO₄ give:
a) Alcohol
b) Diol (glycol)
c) Aldehyde
d) Ketone
Answer: b) Diol (glycol)
Explanation: Mild oxidation forms glycols (cis-diols).
37. Ozonolysis of alkenes gives:
a) Alkanes
b) Alcohols
c) Aldehydes and ketones
d) Acids
Answer: c) Aldehydes and ketones
Explanation: Ozonolysis cleaves double bonds into carbonyl compounds.
38. Alkynes are also called:
a) Acetylenes
b) Olefins
c) Paraffins
d) Aromatics
Answer: a) Acetylenes
Explanation: Alkynes (CnH₂n–2) with triple bonds are called acetylenes.
39. General formula of alkynes is:
a) CnH₂n+2
b) CnH₂n
c) CnH₂n–2
d) CnH₂n–1
Answer: c) CnH₂n–2
Explanation: Alkynes contain one triple bond, general formula CnH₂n–2.
40. The first member of alkynes is:
a) Ethyne
b) Methyne
c) Propyne
d) Butyne
Answer: a) Ethyne
Explanation: Ethyne (C₂H₂), commonly called acetylene, is the first alkyne.
41. Propyne has molecular formula:
a) C₃H₄
b) C₃H₆
c) C₃H₈
d) C₃H₂
Answer: a) C₃H₄
Explanation: Propyne (HC≡C–CH₃) has 3 carbons and 4 hydrogens.
42. Alkynes mainly undergo:
a) Addition reactions
b) Substitution reactions
c) Oxidation only
d) Polymerization only
Answer: a) Addition reactions
Explanation: Alkynes add halogens, hydrogen, and acids across triple bonds.
43. Hydrogenation of ethyne gives:
a) Ethene (partial) → Ethane (complete)
b) Ethane only
c) Methane
d) Propane
Answer: a) Ethene (partial) → Ethane (complete)
Explanation: Ethyne + H₂ → ethene → ethane.
44. Ethyne reacts with chlorine to form:
a) Dichloroethane
b) Tetrachloroethane
c) Both (depending on conditions)
d) None
Answer: c) Both
Explanation: Addition of 1 mole Cl₂ → dichloroethene; 2 moles Cl₂ → tetrachloroethane.
45. Which alkyne is used in oxy-acetylene welding?
a) Methyne
b) Ethyne
c) Propyne
d) Butyne
Answer: b) Ethyne
Explanation: Ethyne burns in oxygen to give high temperature flame (≈ 3500°C).
46. Ethyne with ammoniacal AgNO₃ gives:
a) White precipitate
b) Yellow precipitate
c) Brown precipitate
d) No reaction
Answer: a) White precipitate
Explanation: Terminal alkynes form white precipitate of silver acetylide with AgNO₃.
47. Ethyne with ammoniacal Cu₂Cl₂ gives:
a) Red precipitate
b) Yellow precipitate
c) White precipitate
d) Green precipitate
Answer: a) Red precipitate
Explanation: Terminal alkynes give red precipitate of copper acetylide.
48. Ozonolysis of alkynes gives:
a) Alkanes
b) Alcohols
c) Carboxylic acids
d) Ketones
Answer: c) Carboxylic acids
Explanation: Triple bond cleavage produces acids.
49. Ethyne reacts with water in presence of H₂SO₄ and Hg²⁺ catalyst to form:
a) Ethanol
b) Acetaldehyde
c) Acetone
d) Acetic acid
Answer: b) Acetaldehyde
Explanation: Hydration of ethyne → vinyl alcohol → tautomerizes to acetaldehyde.
50. Which test distinguishes alkanes from alkenes and alkynes?
a) Bromine water test
b) Flame test
c) Neutralization test
d) Distillation
Answer: a) Bromine water test
Explanation: Alkenes/alkynes decolorize bromine water; alkanes do not.
51. Aromatic hydrocarbons contain:
a) Only single bonds
b) Alternating single and double bonds in a ring
c) Only triple bonds
d) Open chain carbon atoms
Answer: b) Alternating single and double bonds in a ring
Explanation: Aromatics follow Huckel’s rule with delocalized π-electrons.
52. Benzene has the molecular formula:
a) C₆H₁₂
b) C₆H₆
c) C₆H₁₀
d) C₆H₈
Answer: b) C₆H₆
Explanation: Benzene has 6 carbons and 6 hydrogens, highly unsaturated but stable.
53. The Kekulé structure of benzene has:
a) Alternating double and single bonds
b) All single bonds
c) All double bonds
d) No bonds
Answer: a) Alternating double and single bonds
Explanation: Kekulé proposed resonance structures for benzene.
54. Benzene is considered aromatic because it follows:
a) Le Chatelier’s principle
b) Hund’s rule
c) Huckel’s rule (4n + 2 π electrons)
d) Pauli’s principle
Answer: c) Huckel’s rule
Explanation: Benzene has 6 π-electrons (n=1) → aromatic stability.
55. Which of the following is a property of benzene?
a) Highly reactive like alkenes
b) Undergoes substitution reactions
c) Always undergoes addition reactions
d) Combines explosively with water
Answer: b) Undergoes substitution reactions
Explanation: Aromatics undergo electrophilic substitution instead of addition (stability retained).
56. The main reaction of benzene is:
a) Addition
b) Substitution
c) Elimination
d) Polymerization
Answer: b) Substitution
Explanation: Benzene maintains aromaticity → undergoes electrophilic substitution.
57. Nitration of benzene gives:
a) Aniline
b) Nitrobenzene
c) Phenol
d) Benzaldehyde
Answer: b) Nitrobenzene
Explanation: Benzene + HNO₃/H₂SO₄ → nitrobenzene.
58. Sulphonation of benzene gives:
a) Benzaldehyde
b) Benzenesulphonic acid
c) Nitrobenzene
d) Benzyl alcohol
Answer: b) Benzenesulphonic acid
Explanation: Benzene + SO₃/H₂SO₄ → benzenesulphonic acid.
59. Friedel–Crafts alkylation uses:
a) AlCl₃ catalyst
b) H₂SO₄ catalyst
c) Pt catalyst
d) Cu catalyst
Answer: a) AlCl₃ catalyst
Explanation: Alkyl halide + benzene → alkylbenzene (catalyst AlCl₃).
60. Friedel–Crafts acylation introduces:
a) Nitro group
b) Alkyl group
c) Acyl group (–COR)
d) Sulphonic group
Answer: c) Acyl group (–COR)
Explanation: Acyl halide + benzene + AlCl₃ → acylbenzene.
61. Toluene is:
a) Methylbenzene
b) Ethylbenzene
c) Dimethylbenzene
d) Benzyl alcohol
Answer: a) Methylbenzene
Explanation: Toluene has a –CH₃ group attached to benzene.
62. On nitration, toluene gives mainly:
a) Ortho- and para-nitrotoluene
b) Meta-nitrotoluene
c) Benzonitrile
d) Dinitrobenzene
Answer: a) Ortho- and para-nitrotoluene
Explanation: –CH₃ group is an ortho/para directing group.
63. Oxidation of toluene with KMnO₄ gives:
a) Benzyl alcohol
b) Benzaldehyde
c) Benzoic acid
d) Phenol
Answer: c) Benzoic acid
Explanation: Side chain oxidation converts –CH₃ into –COOH.
64. Xylene is:
a) Dimethylbenzene
b) Nitrobenzene
c) Benzoic acid
d) Aniline
Answer: a) Dimethylbenzene
Explanation: Xylenes are isomers of C₆H₄(CH₃)₂.
65. The number of xylene isomers is:
a) 2
b) 3
c) 4
d) 5
Answer: b) 3
Explanation: o-xylene, m-xylene, and p-xylene are possible.
66. Naphthalene consists of:
a) One benzene ring
b) Two fused benzene rings
c) Three benzene rings
d) A benzene + cyclohexane ring
Answer: b) Two fused benzene rings
Explanation: Naphthalene has two fused aromatic rings.
67. Anthracene contains:
a) 2 benzene rings
b) 3 linearly fused benzene rings
c) 4 fused benzene rings
d) None
Answer: b) 3 linearly fused benzene rings
Explanation: Anthracene has three fused benzene rings.
68. Phenanthrene contains:
a) 2 fused rings
b) 3 fused rings (angular)
c) 4 fused rings
d) 5 fused rings
Answer: b) 3 fused rings (angular)
Explanation: Phenanthrene has 3 fused benzene rings in an angular structure.
69. Benzene is less reactive towards addition reactions because:
a) It has high resonance energy
b) It is saturated
c) It has weak bonds
d) It has high reactivity
Answer: a) It has high resonance energy
Explanation: Resonance stabilizes benzene, preventing addition.
70. Benzene undergoes chlorination in presence of FeCl₃ to give:
a) Chlorobenzene
b) Benzyl chloride
c) Dichlorobenzene
d) Benzene hexachloride
Answer: a) Chlorobenzene
Explanation: Substitution gives chlorobenzene.
71. Halogenation of benzene requires:
a) UV light
b) Lewis acid catalyst (FeCl₃, AlCl₃)
c) H₂SO₄
d) NaOH
Answer: b) Lewis acid catalyst (FeCl₃, AlCl₃)
Explanation: Catalysts polarize halogens, enabling substitution.
72. TNT (trinitrotoluene) is prepared from toluene by:
a) Sulphonation
b) Nitration
c) Halogenation
d) Oxidation
Answer: b) Nitration
Explanation: Toluene nitrated to 2,4,6-trinitrotoluene (explosive).
73. The product of sulphonation of naphthalene at low temperature is:
a) α-naphthalenesulphonic acid
b) β-naphthalenesulphonic acid
c) Nitro-naphthalene
d) Naphthol
Answer: a) α-naphthalenesulphonic acid
Explanation: Low temperature favours α-substitution.
74. The product of sulphonation of naphthalene at high temperature is:
a) α-naphthalenesulphonic acid
b) β-naphthalenesulphonic acid
c) Dinitronaphthalene
d) Anthracene
Answer: b) β-naphthalenesulphonic acid
Explanation: High temperature favours β-substitution.
75. The most stable aromatic hydrocarbon among the following is:
a) Benzene
b) Toluene
c) Anthracene
d) Naphthalene
Answer: a) Benzene
Explanation: Benzene has maximum resonance stability compared to fused aromatics.
76. The main source of hydrocarbons is:
a) Air
b) Water
c) Petroleum and natural gas
d) Soil
Answer: c) Petroleum and natural gas
Explanation: Hydrocarbons are extracted mainly from crude oil and natural gas reserves.
77. Petroleum is a mixture of:
a) Alkanes only
b) Alkanes, cycloalkanes, and aromatics
c) Alcohols and acids
d) Esters
Answer: b) Alkanes, cycloalkanes, and aromatics
Explanation: Crude oil contains various hydrocarbons, refined into fuels and chemicals.
78. The process of separating petroleum into useful fractions is:
a) Cracking
b) Distillation
c) Refining
d) Fractional distillation
Answer: d) Fractional distillation
Explanation: Petroleum is separated by fractional distillation based on boiling points.
79. LPG is a mixture of:
a) Methane and ethane
b) Propane and butane
c) Ethylene and acetylene
d) Benzene and toluene
Answer: b) Propane and butane
Explanation: LPG (cooking gas) contains mainly propane and butane.
80. CNG mainly contains:
a) Methane
b) Ethane
c) Propane
d) Butane
Answer: a) Methane
Explanation: Compressed Natural Gas is methane-rich and a clean fuel.
81. Which hydrocarbon is used for welding purposes?
a) Methane
b) Ethane
c) Ethyne
d) Propane
Answer: c) Ethyne
Explanation: Ethyne (acetylene) burns in oxygen to give a hot flame (~3500°C).
82. Petrol is obtained from:
a) Light fraction of petroleum
b) Heavy fraction of petroleum
c) Coal tar
d) Natural gas only
Answer: a) Light fraction of petroleum
Explanation: Petrol (gasoline) comes from lighter fractions during refining.
83. Kerosene belongs to:
a) Lighter fractions of petroleum
b) Middle fractions of petroleum
c) Heavy fractions of petroleum
d) Residue
Answer: b) Middle fractions of petroleum
Explanation: Kerosene is in the middle distillate range.
84. Diesel is obtained from:
a) Residue
b) Middle fraction
c) Light fraction
d) Gaseous fraction
Answer: b) Middle fraction
Explanation: Diesel is heavier than kerosene but lighter than lubricating oils.
85. The heaviest fraction obtained from petroleum distillation is:
a) Petrol
b) Diesel
c) Bitumen
d) Kerosene
Answer: c) Bitumen
Explanation: Bitumen (asphalt) is the residue after fractional distillation.
86. The process of breaking higher hydrocarbons into lower ones is:
a) Polymerization
b) Cracking
c) Distillation
d) Refining
Answer: b) Cracking
Explanation: Cracking breaks heavy hydrocarbons into lighter alkanes/alkenes.
87. Which process improves the octane number of petrol?
a) Cracking
b) Reforming
c) Hydrogenation
d) Distillation
Answer: b) Reforming
Explanation: Catalytic reforming increases branching → higher octane rating.
88. Polymerization of ethene gives:
a) Polyethene
b) Polypropylene
c) Polystyrene
d) Teflon
Answer: a) Polyethene
Explanation: Ethene polymerizes to form polyethylene (plastic bags, bottles).
89. Polymerization of propene gives:
a) Polyethene
b) Polypropylene
c) Polystyrene
d) PVC
Answer: b) Polypropylene
Explanation: Propene polymerizes to polypropylene (ropes, packaging).
90. Polymerization of vinyl chloride gives:
a) PVC
b) Polyethene
c) Polypropylene
d) Nylon
Answer: a) PVC
Explanation: Vinyl chloride → polyvinyl chloride (PVC) used in pipes, insulation.
91. Polymerization of styrene gives:
a) Nylon
b) Teflon
c) Polystyrene
d) Polyester
Answer: c) Polystyrene
Explanation: Styrene polymerizes into polystyrene (disposable cups, packaging).
92. Teflon is obtained by polymerization of:
a) Ethene
b) Propene
c) Tetrafluoroethene
d) Vinyl chloride
Answer: c) Tetrafluoroethene
Explanation: Teflon (non-stick coating) is PTFE from tetrafluoroethene.
93. The main hydrocarbon in coal gas is:
a) Methane
b) Hydrogen
c) Carbon monoxide
d) A mixture of all
Answer: d) A mixture of all
Explanation: Coal gas has CH₄, H₂, and CO.
94. Water gas is a mixture of:
a) CO and H₂
b) CO₂ and H₂
c) CH₄ and CO₂
d) CO and CH₄
Answer: a) CO and H₂
Explanation: Water gas = CO + H₂, used as fuel.
95. Producer gas is a mixture of:
a) CO + H₂
b) CO + N₂
c) H₂ + CH₄
d) CO₂ + N₂
Answer: b) CO + N₂
Explanation: Producer gas is CO + N₂ from coal with air.
96. Coal tar contains:
a) Alkanes only
b) Aromatic hydrocarbons like benzene, naphthalene, anthracene
c) Alcohols only
d) Acids only
Answer: b) Aromatic hydrocarbons
Explanation: Coal tar is a source of aromatic hydrocarbons and dyes.
97. The high calorific value of hydrocarbons is due to:
a) Presence of oxygen
b) Presence of hydrogen and carbon bonds
c) Presence of nitrogen
d) Presence of sulphur
Answer: b) Presence of hydrogen and carbon bonds
Explanation: Hydrocarbons release large energy on combustion (CO₂ + H₂O).
98. Which hydrocarbon derivative is used as anaesthetic (“laughing gas”)?
a) CO
b) N₂O
c) CHCl₃
d) C₂H₂
Answer: b) N₂O
Explanation: Nitrous oxide (not a hydrocarbon itself but derivative) is used in anaesthesia.
99. Which hydrocarbon is known as “dry ice” when solidified?
a) Methane
b) Carbon dioxide
c) Ethane
d) Butane
Answer: b) Carbon dioxide
Explanation: Though CO₂ is not a hydrocarbon, it is an important carbon compound often studied alongside fuels.
100. The main environmental effect of burning hydrocarbons is:
a) Ozone depletion
b) Air pollution and greenhouse effect (CO₂, CO emissions)
c) Soil fertility increase
d) Acid rain only
Answer: b) Air pollution and greenhouse effect
Explanation: Hydrocarbon combustion → CO₂ (global warming), CO, NOx (pollution).