Hydrocarbons Practice

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NEET Chemistry - Chapter 14

Hydrocarbons Practice Tests

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Alkanes
1. General formula of acyclic alkanes is:
- A. C$_n$H$_{2n+2}$ (Correct)
- B. C$_n$H$_{2n}$
- C. C$_n$H$_{2n-2}$
- D. C$_n$H$_{2n+1}$
Explanation: Alkanes are saturated open-chain hydrocarbons.
Alkenes
2. General formula of acyclic alkenes is:
- A. C$_n$H$_{2n}$ (Correct)
- B. C$_n$H$_{2n+2}$
- C. C$_n$H$_{2n-2}$
- D. C$_n$H$_{n}$
Explanation: One double bond reduces two hydrogens relative to alkanes.
Alkynes
3. General formula of acyclic alkynes is:
- A. C$_n$H$_{2n-2}$ (Correct)
- B. C$_n$H$_{2n}$
- C. C$_n$H$_{2n+2}$
- D. C$_n$H$_{n}$
Explanation: One triple bond reduces four hydrogens relative to alkanes.
Hybridization
4. Carbon atoms involved in a double bond are generally:
- A. sp$^2$ hybridized (Correct)
- B. sp$^3$ hybridized
- C. sp hybridized
- D. dsp$^2$ hybridized
Explanation: Each carbon in a C=C bond is trigonal planar.
Hybridization
5. Carbon atoms involved in a triple bond are generally:
- A. sp hybridized (Correct)
- B. sp$^2$ hybridized
- C. sp$^3$ hybridized
- D. d$^2$sp$^3$
Explanation: Each carbon in C≡C is linear.
Alkane reaction
6. The characteristic reaction of alkanes is:
- A. free-radical substitution (Correct)
- B. electrophilic addition
- C. nucleophilic addition
- D. hydration across double bond
Explanation: Halogenation of alkanes proceeds via radicals.
Alkene reaction
7. The characteristic reaction of alkenes is:
- A. electrophilic addition (Correct)
- B. free-radical substitution
- C. nucleophilic substitution only
- D. elimination only
Explanation: The electron-rich pi bond attracts electrophiles.
Markovnikov
8. Markovnikov's rule predicts addition of HX to unsymmetrical alkene so that H attaches to the carbon having:
- A. more hydrogens already (Correct)
- B. fewer hydrogens already
- C. greater mass
- D. more lone pairs
Explanation: The halide goes to the more substituted carbon under normal addition.
Peroxide effect
9. Peroxide effect is observed prominently with:
- A. HBr (Correct)
- B. HCl
- C. HI
- D. HF
Explanation: Anti-Markovnikov radical addition is classically observed for HBr.
Ozonolysis
10. Ozonolysis of alkenes is used to locate:
- A. position of double bond (Correct)
- B. number of neutrons
- C. hybridization of hydrogen
- D. ionic strength
Explanation: Cleavage products reveal the original alkene structure.
Bromine test
11. Decolourisation of bromine water usually indicates presence of:
- A. unsaturation (Correct)
- B. alkane only
- C. noble gas
- D. ionic solid
Explanation: Alkenes and alkynes add bromine across multiple bonds.
Baeyer's test
12. Cold dilute alkaline KMnO$_4$ is used to test for:
- A. unsaturation (Correct)
- B. only aromaticity
- C. alkane purity
- D. molar mass
Explanation: It is a classical qualitative test for double or triple bonds.
Aromaticity
13. Benzene is especially stable because it is:
- A. aromatic with delocalized pi electrons (Correct)
- B. an alkane
- C. a radical
- D. an ionic solid
Explanation: Delocalized cyclic pi electrons give aromatic stabilization.
Benzene reaction
14. Characteristic reaction of benzene is:
- A. electrophilic substitution (Correct)
- B. electrophilic addition
- C. free-radical addition
- D. nucleophilic elimination
Explanation: Benzene preserves aromaticity by substitution rather than addition.
Nitration
15. Nitration of benzene uses concentrated nitric acid in presence of:
- A. concentrated sulfuric acid (Correct)
- B. sodium hydroxide
- C. zinc dust
- D. water
Explanation: Sulfuric acid helps generate the nitronium ion.
Halogenation
16. Chlorination of methane in sunlight proceeds by:
- A. free-radical chain mechanism (Correct)
- B. ionic mechanism only
- C. nucleophilic addition
- D. catalyst poisoning
Explanation: UV light or heat initiates radical formation.
Acidity
17. Terminal alkynes are more acidic than alkenes mainly because the carbon is:
- A. sp hybridized (Correct)
- B. sp$^3$ hybridized
- C. sp$^2$ hybridized with resonance
- D. ionic
Explanation: Higher s-character stabilizes the conjugate base.
Combustion
18. Complete combustion of hydrocarbons generally yields:
- A. CO$_2$ and H$_2$O (Correct)
- B. CO and H$_2$ only
- C. C and O$_2$
- D. only water
Explanation: Full combustion produces carbon dioxide and water.
Isomerism
19. Geometrical isomerism is shown by many:
- A. alkenes (Correct)
- B. alkanes only
- C. alkynes only
- D. noble gases
Explanation: Restricted rotation around C=C allows cis-trans isomerism.
Stability
20. Among alkenes, greater substitution generally makes the double bond:
- A. more stable (Correct)
- B. less stable
- C. unchanged
- D. ionic
Explanation: Hyperconjugation and alkyl donation stabilize substituted alkenes.
Polymerization
21. Ethene can undergo polymerization to form:
- A. polyethene (Correct)
- B. benzene
- C. ethyne
- D. graphite
Explanation: Addition polymerization of ethene gives polyethene.
Aromatic rule
22. Benzene is aromatic because it has:
- A. 6 pi electrons in a planar cyclic conjugated system (Correct)
- B. 8 pi electrons
- C. only sigma electrons
- D. sp$^3$ carbons only
Explanation: It follows Hückel's 4n+2 rule with n = 1.
Reaction logic
23. Alkynes can show addition reactions because they contain:
- A. two pi bonds (Correct)
- B. only sigma bonds
- C. ionic bonds
- D. hydrogen bonds
Explanation: Multiple bonds offer sites for addition.
Concept summary
24. The most useful split in hydrocarbon chemistry is saturated vs unsaturated because it predicts:
- A. reaction type (Correct)
- B. only color
- C. only density
- D. melting point only
Explanation: Saturation level strongly controls reactivity.
Hydrocarbon logic
25. A quick NEET route in hydrocarbons is to classify the substrate as alkane, alkene, alkyne, or aromatic, then recall the chapter’s:
- A. signature reaction pattern (Correct)
- B. molar conductivity
- C. lattice enthalpy
- D. electrode potential
Explanation: Each family has a characteristic style of reactivity.
Alkanes
26. General formula of acyclic alkanes is:
- A. C$_n$H$_{2n+2}$ (Correct)
- B. C$_n$H$_{2n}$
- C. C$_n$H$_{2n-2}$
- D. C$_n$H$_{2n+1}$
Explanation: Alkanes are saturated open-chain hydrocarbons.
Alkenes
27. General formula of acyclic alkenes is:
- A. C$_n$H$_{2n}$ (Correct)
- B. C$_n$H$_{2n+2}$
- C. C$_n$H$_{2n-2}$
- D. C$_n$H$_{n}$
Explanation: One double bond reduces two hydrogens relative to alkanes.
Alkynes
28. General formula of acyclic alkynes is:
- A. C$_n$H$_{2n-2}$ (Correct)
- B. C$_n$H$_{2n}$
- C. C$_n$H$_{2n+2}$
- D. C$_n$H$_{n}$
Explanation: One triple bond reduces four hydrogens relative to alkanes.
Hybridization
29. Carbon atoms involved in a double bond are generally:
- A. sp$^2$ hybridized (Correct)
- B. sp$^3$ hybridized
- C. sp hybridized
- D. dsp$^2$ hybridized
Explanation: Each carbon in a C=C bond is trigonal planar.
Hybridization
30. Carbon atoms involved in a triple bond are generally:
- A. sp hybridized (Correct)
- B. sp$^2$ hybridized
- C. sp$^3$ hybridized
- D. d$^2$sp$^3$
Explanation: Each carbon in C≡C is linear.
Alkane reaction
31. The characteristic reaction of alkanes is:
- A. free-radical substitution (Correct)
- B. electrophilic addition
- C. nucleophilic addition
- D. hydration across double bond
Explanation: Halogenation of alkanes proceeds via radicals.
Alkene reaction
32. The characteristic reaction of alkenes is:
- A. electrophilic addition (Correct)
- B. free-radical substitution
- C. nucleophilic substitution only
- D. elimination only
Explanation: The electron-rich pi bond attracts electrophiles.
Markovnikov
33. Markovnikov's rule predicts addition of HX to unsymmetrical alkene so that H attaches to the carbon having:
- A. more hydrogens already (Correct)
- B. fewer hydrogens already
- C. greater mass
- D. more lone pairs
Explanation: The halide goes to the more substituted carbon under normal addition.
Peroxide effect
34. Peroxide effect is observed prominently with:
- A. HBr (Correct)
- B. HCl
- C. HI
- D. HF
Explanation: Anti-Markovnikov radical addition is classically observed for HBr.
Ozonolysis
35. Ozonolysis of alkenes is used to locate:
- A. position of double bond (Correct)
- B. number of neutrons
- C. hybridization of hydrogen
- D. ionic strength
Explanation: Cleavage products reveal the original alkene structure.
Bromine test
36. Decolourisation of bromine water usually indicates presence of:
- A. unsaturation (Correct)
- B. alkane only
- C. noble gas
- D. ionic solid
Explanation: Alkenes and alkynes add bromine across multiple bonds.
Baeyer's test
37. Cold dilute alkaline KMnO$_4$ is used to test for:
- A. unsaturation (Correct)
- B. only aromaticity
- C. alkane purity
- D. molar mass
Explanation: It is a classical qualitative test for double or triple bonds.
Aromaticity
38. Benzene is especially stable because it is:
- A. aromatic with delocalized pi electrons (Correct)
- B. an alkane
- C. a radical
- D. an ionic solid
Explanation: Delocalized cyclic pi electrons give aromatic stabilization.
Benzene reaction
39. Characteristic reaction of benzene is:
- A. electrophilic substitution (Correct)
- B. electrophilic addition
- C. free-radical addition
- D. nucleophilic elimination
Explanation: Benzene preserves aromaticity by substitution rather than addition.
Nitration
40. Nitration of benzene uses concentrated nitric acid in presence of:
- A. concentrated sulfuric acid (Correct)
- B. sodium hydroxide
- C. zinc dust
- D. water
Explanation: Sulfuric acid helps generate the nitronium ion.
Halogenation
41. Chlorination of methane in sunlight proceeds by:
- A. free-radical chain mechanism (Correct)
- B. ionic mechanism only
- C. nucleophilic addition
- D. catalyst poisoning
Explanation: UV light or heat initiates radical formation.
Acidity
42. Terminal alkynes are more acidic than alkenes mainly because the carbon is:
- A. sp hybridized (Correct)
- B. sp$^3$ hybridized
- C. sp$^2$ hybridized with resonance
- D. ionic
Explanation: Higher s-character stabilizes the conjugate base.
Combustion
43. Complete combustion of hydrocarbons generally yields:
- A. CO$_2$ and H$_2$O (Correct)
- B. CO and H$_2$ only
- C. C and O$_2$
- D. only water
Explanation: Full combustion produces carbon dioxide and water.
Isomerism
44. Geometrical isomerism is shown by many:
- A. alkenes (Correct)
- B. alkanes only
- C. alkynes only
- D. noble gases
Explanation: Restricted rotation around C=C allows cis-trans isomerism.
Stability
45. Among alkenes, greater substitution generally makes the double bond:
- A. more stable (Correct)
- B. less stable
- C. unchanged
- D. ionic
Explanation: Hyperconjugation and alkyl donation stabilize substituted alkenes.
Polymerization
46. Ethene can undergo polymerization to form:
- A. polyethene (Correct)
- B. benzene
- C. ethyne
- D. graphite
Explanation: Addition polymerization of ethene gives polyethene.
Aromatic rule
47. Benzene is aromatic because it has:
- A. 6 pi electrons in a planar cyclic conjugated system (Correct)
- B. 8 pi electrons
- C. only sigma electrons
- D. sp$^3$ carbons only
Explanation: It follows Hückel's 4n+2 rule with n = 1.
Reaction logic
48. Alkynes can show addition reactions because they contain:
- A. two pi bonds (Correct)
- B. only sigma bonds
- C. ionic bonds
- D. hydrogen bonds
Explanation: Multiple bonds offer sites for addition.
Concept summary
49. The most useful split in hydrocarbon chemistry is saturated vs unsaturated because it predicts:
- A. reaction type (Correct)
- B. only color
- C. only density
- D. melting point only
Explanation: Saturation level strongly controls reactivity.
Hydrocarbon logic
50. A quick NEET route in hydrocarbons is to classify the substrate as alkane, alkene, alkyne, or aromatic, then recall the chapter’s:
- A. signature reaction pattern (Correct)
- B. molar conductivity
- C. lattice enthalpy
- D. electrode potential
Explanation: Each family has a characteristic style of reactivity.
Alkanes
51. General formula of acyclic alkanes is:
- A. C$_n$H$_{2n+2}$ (Correct)
- B. C$_n$H$_{2n}$
- C. C$_n$H$_{2n-2}$
- D. C$_n$H$_{2n+1}$
Explanation: Alkanes are saturated open-chain hydrocarbons.
Alkenes
52. General formula of acyclic alkenes is:
- A. C$_n$H$_{2n}$ (Correct)
- B. C$_n$H$_{2n+2}$
- C. C$_n$H$_{2n-2}$
- D. C$_n$H$_{n}$
Explanation: One double bond reduces two hydrogens relative to alkanes.
Alkynes
53. General formula of acyclic alkynes is:
- A. C$_n$H$_{2n-2}$ (Correct)
- B. C$_n$H$_{2n}$
- C. C$_n$H$_{2n+2}$
- D. C$_n$H$_{n}$
Explanation: One triple bond reduces four hydrogens relative to alkanes.
Hybridization
54. Carbon atoms involved in a double bond are generally:
- A. sp$^2$ hybridized (Correct)
- B. sp$^3$ hybridized
- C. sp hybridized
- D. dsp$^2$ hybridized
Explanation: Each carbon in a C=C bond is trigonal planar.
Hybridization
55. Carbon atoms involved in a triple bond are generally:
- A. sp hybridized (Correct)
- B. sp$^2$ hybridized
- C. sp$^3$ hybridized
- D. d$^2$sp$^3$
Explanation: Each carbon in C≡C is linear.
Alkane reaction
56. The characteristic reaction of alkanes is:
- A. free-radical substitution (Correct)
- B. electrophilic addition
- C. nucleophilic addition
- D. hydration across double bond
Explanation: Halogenation of alkanes proceeds via radicals.
Alkene reaction
57. The characteristic reaction of alkenes is:
- A. electrophilic addition (Correct)
- B. free-radical substitution
- C. nucleophilic substitution only
- D. elimination only
Explanation: The electron-rich pi bond attracts electrophiles.
Markovnikov
58. Markovnikov's rule predicts addition of HX to unsymmetrical alkene so that H attaches to the carbon having:
- A. more hydrogens already (Correct)
- B. fewer hydrogens already
- C. greater mass
- D. more lone pairs
Explanation: The halide goes to the more substituted carbon under normal addition.
Peroxide effect
59. Peroxide effect is observed prominently with:
- A. HBr (Correct)
- B. HCl
- C. HI
- D. HF
Explanation: Anti-Markovnikov radical addition is classically observed for HBr.
Ozonolysis
60. Ozonolysis of alkenes is used to locate:
- A. position of double bond (Correct)
- B. number of neutrons
- C. hybridization of hydrogen
- D. ionic strength
Explanation: Cleavage products reveal the original alkene structure.
Bromine test
61. Decolourisation of bromine water usually indicates presence of:
- A. unsaturation (Correct)
- B. alkane only
- C. noble gas
- D. ionic solid
Explanation: Alkenes and alkynes add bromine across multiple bonds.
Baeyer's test
62. Cold dilute alkaline KMnO$_4$ is used to test for:
- A. unsaturation (Correct)
- B. only aromaticity
- C. alkane purity
- D. molar mass
Explanation: It is a classical qualitative test for double or triple bonds.
Aromaticity
63. Benzene is especially stable because it is:
- A. aromatic with delocalized pi electrons (Correct)
- B. an alkane
- C. a radical
- D. an ionic solid
Explanation: Delocalized cyclic pi electrons give aromatic stabilization.
Benzene reaction
64. Characteristic reaction of benzene is:
- A. electrophilic substitution (Correct)
- B. electrophilic addition
- C. free-radical addition
- D. nucleophilic elimination
Explanation: Benzene preserves aromaticity by substitution rather than addition.
Nitration
65. Nitration of benzene uses concentrated nitric acid in presence of:
- A. concentrated sulfuric acid (Correct)
- B. sodium hydroxide
- C. zinc dust
- D. water
Explanation: Sulfuric acid helps generate the nitronium ion.
Halogenation
66. Chlorination of methane in sunlight proceeds by:
- A. free-radical chain mechanism (Correct)
- B. ionic mechanism only
- C. nucleophilic addition
- D. catalyst poisoning
Explanation: UV light or heat initiates radical formation.
Acidity
67. Terminal alkynes are more acidic than alkenes mainly because the carbon is:
- A. sp hybridized (Correct)
- B. sp$^3$ hybridized
- C. sp$^2$ hybridized with resonance
- D. ionic
Explanation: Higher s-character stabilizes the conjugate base.
Combustion
68. Complete combustion of hydrocarbons generally yields:
- A. CO$_2$ and H$_2$O (Correct)
- B. CO and H$_2$ only
- C. C and O$_2$
- D. only water
Explanation: Full combustion produces carbon dioxide and water.
Isomerism
69. Geometrical isomerism is shown by many:
- A. alkenes (Correct)
- B. alkanes only
- C. alkynes only
- D. noble gases
Explanation: Restricted rotation around C=C allows cis-trans isomerism.
Stability
70. Among alkenes, greater substitution generally makes the double bond:
- A. more stable (Correct)
- B. less stable
- C. unchanged
- D. ionic
Explanation: Hyperconjugation and alkyl donation stabilize substituted alkenes.
Polymerization
71. Ethene can undergo polymerization to form:
- A. polyethene (Correct)
- B. benzene
- C. ethyne
- D. graphite
Explanation: Addition polymerization of ethene gives polyethene.
Aromatic rule
72. Benzene is aromatic because it has:
- A. 6 pi electrons in a planar cyclic conjugated system (Correct)
- B. 8 pi electrons
- C. only sigma electrons
- D. sp$^3$ carbons only
Explanation: It follows Hückel's 4n+2 rule with n = 1.
Reaction logic
73. Alkynes can show addition reactions because they contain:
- A. two pi bonds (Correct)
- B. only sigma bonds
- C. ionic bonds
- D. hydrogen bonds
Explanation: Multiple bonds offer sites for addition.
Concept summary
74. The most useful split in hydrocarbon chemistry is saturated vs unsaturated because it predicts:
- A. reaction type (Correct)
- B. only color
- C. only density
- D. melting point only
Explanation: Saturation level strongly controls reactivity.
Hydrocarbon logic
75. A quick NEET route in hydrocarbons is to classify the substrate as alkane, alkene, alkyne, or aromatic, then recall the chapter’s:
- A. signature reaction pattern (Correct)
- B. molar conductivity
- C. lattice enthalpy
- D. electrode potential
Explanation: Each family has a characteristic style of reactivity.
Alkanes
76. General formula of acyclic alkanes is:
- A. C$_n$H$_{2n+2}$ (Correct)
- B. C$_n$H$_{2n}$
- C. C$_n$H$_{2n-2}$
- D. C$_n$H$_{2n+1}$
Explanation: Alkanes are saturated open-chain hydrocarbons.
Alkenes
77. General formula of acyclic alkenes is:
- A. C$_n$H$_{2n}$ (Correct)
- B. C$_n$H$_{2n+2}$
- C. C$_n$H$_{2n-2}$
- D. C$_n$H$_{n}$
Explanation: One double bond reduces two hydrogens relative to alkanes.
Alkynes
78. General formula of acyclic alkynes is:
- A. C$_n$H$_{2n-2}$ (Correct)
- B. C$_n$H$_{2n}$
- C. C$_n$H$_{2n+2}$
- D. C$_n$H$_{n}$
Explanation: One triple bond reduces four hydrogens relative to alkanes.
Hybridization
79. Carbon atoms involved in a double bond are generally:
- A. sp$^2$ hybridized (Correct)
- B. sp$^3$ hybridized
- C. sp hybridized
- D. dsp$^2$ hybridized
Explanation: Each carbon in a C=C bond is trigonal planar.
Hybridization
80. Carbon atoms involved in a triple bond are generally:
- A. sp hybridized (Correct)
- B. sp$^2$ hybridized
- C. sp$^3$ hybridized
- D. d$^2$sp$^3$
Explanation: Each carbon in C≡C is linear.
Alkane reaction
81. The characteristic reaction of alkanes is:
- A. free-radical substitution (Correct)
- B. electrophilic addition
- C. nucleophilic addition
- D. hydration across double bond
Explanation: Halogenation of alkanes proceeds via radicals.
Alkene reaction
82. The characteristic reaction of alkenes is:
- A. electrophilic addition (Correct)
- B. free-radical substitution
- C. nucleophilic substitution only
- D. elimination only
Explanation: The electron-rich pi bond attracts electrophiles.
Markovnikov
83. Markovnikov's rule predicts addition of HX to unsymmetrical alkene so that H attaches to the carbon having:
- A. more hydrogens already (Correct)
- B. fewer hydrogens already
- C. greater mass
- D. more lone pairs
Explanation: The halide goes to the more substituted carbon under normal addition.
Peroxide effect
84. Peroxide effect is observed prominently with:
- A. HBr (Correct)
- B. HCl
- C. HI
- D. HF
Explanation: Anti-Markovnikov radical addition is classically observed for HBr.
Ozonolysis
85. Ozonolysis of alkenes is used to locate:
- A. position of double bond (Correct)
- B. number of neutrons
- C. hybridization of hydrogen
- D. ionic strength
Explanation: Cleavage products reveal the original alkene structure.
Bromine test
86. Decolourisation of bromine water usually indicates presence of:
- A. unsaturation (Correct)
- B. alkane only
- C. noble gas
- D. ionic solid
Explanation: Alkenes and alkynes add bromine across multiple bonds.
Baeyer's test
87. Cold dilute alkaline KMnO$_4$ is used to test for:
- A. unsaturation (Correct)
- B. only aromaticity
- C. alkane purity
- D. molar mass
Explanation: It is a classical qualitative test for double or triple bonds.
Aromaticity
88. Benzene is especially stable because it is:
- A. aromatic with delocalized pi electrons (Correct)
- B. an alkane
- C. a radical
- D. an ionic solid
Explanation: Delocalized cyclic pi electrons give aromatic stabilization.
Benzene reaction
89. Characteristic reaction of benzene is:
- A. electrophilic substitution (Correct)
- B. electrophilic addition
- C. free-radical addition
- D. nucleophilic elimination
Explanation: Benzene preserves aromaticity by substitution rather than addition.
Nitration
90. Nitration of benzene uses concentrated nitric acid in presence of:
- A. concentrated sulfuric acid (Correct)
- B. sodium hydroxide
- C. zinc dust
- D. water
Explanation: Sulfuric acid helps generate the nitronium ion.
Halogenation
91. Chlorination of methane in sunlight proceeds by:
- A. free-radical chain mechanism (Correct)
- B. ionic mechanism only
- C. nucleophilic addition
- D. catalyst poisoning
Explanation: UV light or heat initiates radical formation.
Acidity
92. Terminal alkynes are more acidic than alkenes mainly because the carbon is:
- A. sp hybridized (Correct)
- B. sp$^3$ hybridized
- C. sp$^2$ hybridized with resonance
- D. ionic
Explanation: Higher s-character stabilizes the conjugate base.
Combustion
93. Complete combustion of hydrocarbons generally yields:
- A. CO$_2$ and H$_2$O (Correct)
- B. CO and H$_2$ only
- C. C and O$_2$
- D. only water
Explanation: Full combustion produces carbon dioxide and water.
Isomerism
94. Geometrical isomerism is shown by many:
- A. alkenes (Correct)
- B. alkanes only
- C. alkynes only
- D. noble gases
Explanation: Restricted rotation around C=C allows cis-trans isomerism.
Stability
95. Among alkenes, greater substitution generally makes the double bond:
- A. more stable (Correct)
- B. less stable
- C. unchanged
- D. ionic
Explanation: Hyperconjugation and alkyl donation stabilize substituted alkenes.
Polymerization
96. Ethene can undergo polymerization to form:
- A. polyethene (Correct)
- B. benzene
- C. ethyne
- D. graphite
Explanation: Addition polymerization of ethene gives polyethene.
Aromatic rule
97. Benzene is aromatic because it has:
- A. 6 pi electrons in a planar cyclic conjugated system (Correct)
- B. 8 pi electrons
- C. only sigma electrons
- D. sp$^3$ carbons only
Explanation: It follows Hückel's 4n+2 rule with n = 1.
Reaction logic
98. Alkynes can show addition reactions because they contain:
- A. two pi bonds (Correct)
- B. only sigma bonds
- C. ionic bonds
- D. hydrogen bonds
Explanation: Multiple bonds offer sites for addition.
Concept summary
99. The most useful split in hydrocarbon chemistry is saturated vs unsaturated because it predicts:
- A. reaction type (Correct)
- B. only color
- C. only density
- D. melting point only
Explanation: Saturation level strongly controls reactivity.
Hydrocarbon logic
100. A quick NEET route in hydrocarbons is to classify the substrate as alkane, alkene, alkyne, or aromatic, then recall the chapter’s:
- A. signature reaction pattern (Correct)
- B. molar conductivity
- C. lattice enthalpy
- D. electrode potential
Explanation: Each family has a characteristic style of reactivity.
Alkanes
101. General formula of acyclic alkanes is:
- A. C$_n$H$_{2n+2}$ (Correct)
- B. C$_n$H$_{2n}$
- C. C$_n$H$_{2n-2}$
- D. C$_n$H$_{2n+1}$
Explanation: Alkanes are saturated open-chain hydrocarbons.
Alkenes
102. General formula of acyclic alkenes is:
- A. C$_n$H$_{2n}$ (Correct)
- B. C$_n$H$_{2n+2}$
- C. C$_n$H$_{2n-2}$
- D. C$_n$H$_{n}$
Explanation: One double bond reduces two hydrogens relative to alkanes.
Alkynes
103. General formula of acyclic alkynes is:
- A. C$_n$H$_{2n-2}$ (Correct)
- B. C$_n$H$_{2n}$
- C. C$_n$H$_{2n+2}$
- D. C$_n$H$_{n}$
Explanation: One triple bond reduces four hydrogens relative to alkanes.
Hybridization
104. Carbon atoms involved in a double bond are generally:
- A. sp$^2$ hybridized (Correct)
- B. sp$^3$ hybridized
- C. sp hybridized
- D. dsp$^2$ hybridized
Explanation: Each carbon in a C=C bond is trigonal planar.
Hybridization
105. Carbon atoms involved in a triple bond are generally:
- A. sp hybridized (Correct)
- B. sp$^2$ hybridized
- C. sp$^3$ hybridized
- D. d$^2$sp$^3$
Explanation: Each carbon in C≡C is linear.
Alkane reaction
106. The characteristic reaction of alkanes is:
- A. free-radical substitution (Correct)
- B. electrophilic addition
- C. nucleophilic addition
- D. hydration across double bond
Explanation: Halogenation of alkanes proceeds via radicals.
Alkene reaction
107. The characteristic reaction of alkenes is:
- A. electrophilic addition (Correct)
- B. free-radical substitution
- C. nucleophilic substitution only
- D. elimination only
Explanation: The electron-rich pi bond attracts electrophiles.
Markovnikov
108. Markovnikov's rule predicts addition of HX to unsymmetrical alkene so that H attaches to the carbon having:
- A. more hydrogens already (Correct)
- B. fewer hydrogens already
- C. greater mass
- D. more lone pairs
Explanation: The halide goes to the more substituted carbon under normal addition.
Peroxide effect
109. Peroxide effect is observed prominently with:
- A. HBr (Correct)
- B. HCl
- C. HI
- D. HF
Explanation: Anti-Markovnikov radical addition is classically observed for HBr.
Ozonolysis
110. Ozonolysis of alkenes is used to locate:
- A. position of double bond (Correct)
- B. number of neutrons
- C. hybridization of hydrogen
- D. ionic strength
Explanation: Cleavage products reveal the original alkene structure.
Bromine test
111. Decolourisation of bromine water usually indicates presence of:
- A. unsaturation (Correct)
- B. alkane only
- C. noble gas
- D. ionic solid
Explanation: Alkenes and alkynes add bromine across multiple bonds.
Baeyer's test
112. Cold dilute alkaline KMnO$_4$ is used to test for:
- A. unsaturation (Correct)
- B. only aromaticity
- C. alkane purity
- D. molar mass
Explanation: It is a classical qualitative test for double or triple bonds.
Aromaticity
113. Benzene is especially stable because it is:
- A. aromatic with delocalized pi electrons (Correct)
- B. an alkane
- C. a radical
- D. an ionic solid
Explanation: Delocalized cyclic pi electrons give aromatic stabilization.
Benzene reaction
114. Characteristic reaction of benzene is:
- A. electrophilic substitution (Correct)
- B. electrophilic addition
- C. free-radical addition
- D. nucleophilic elimination
Explanation: Benzene preserves aromaticity by substitution rather than addition.
Nitration
115. Nitration of benzene uses concentrated nitric acid in presence of:
- A. concentrated sulfuric acid (Correct)
- B. sodium hydroxide
- C. zinc dust
- D. water
Explanation: Sulfuric acid helps generate the nitronium ion.
Halogenation
116. Chlorination of methane in sunlight proceeds by:
- A. free-radical chain mechanism (Correct)
- B. ionic mechanism only
- C. nucleophilic addition
- D. catalyst poisoning
Explanation: UV light or heat initiates radical formation.
Acidity
117. Terminal alkynes are more acidic than alkenes mainly because the carbon is:
- A. sp hybridized (Correct)
- B. sp$^3$ hybridized
- C. sp$^2$ hybridized with resonance
- D. ionic
Explanation: Higher s-character stabilizes the conjugate base.
Combustion
118. Complete combustion of hydrocarbons generally yields:
- A. CO$_2$ and H$_2$O (Correct)
- B. CO and H$_2$ only
- C. C and O$_2$
- D. only water
Explanation: Full combustion produces carbon dioxide and water.
Isomerism
119. Geometrical isomerism is shown by many:
- A. alkenes (Correct)
- B. alkanes only
- C. alkynes only
- D. noble gases
Explanation: Restricted rotation around C=C allows cis-trans isomerism.
Stability
120. Among alkenes, greater substitution generally makes the double bond:
- A. more stable (Correct)
- B. less stable
- C. unchanged
- D. ionic
Explanation: Hyperconjugation and alkyl donation stabilize substituted alkenes.
Polymerization
121. Ethene can undergo polymerization to form:
- A. polyethene (Correct)
- B. benzene
- C. ethyne
- D. graphite
Explanation: Addition polymerization of ethene gives polyethene.
Aromatic rule
122. Benzene is aromatic because it has:
- A. 6 pi electrons in a planar cyclic conjugated system (Correct)
- B. 8 pi electrons
- C. only sigma electrons
- D. sp$^3$ carbons only
Explanation: It follows Hückel's 4n+2 rule with n = 1.
Reaction logic
123. Alkynes can show addition reactions because they contain:
- A. two pi bonds (Correct)
- B. only sigma bonds
- C. ionic bonds
- D. hydrogen bonds
Explanation: Multiple bonds offer sites for addition.
Concept summary
124. The most useful split in hydrocarbon chemistry is saturated vs unsaturated because it predicts:
- A. reaction type (Correct)
- B. only color
- C. only density
- D. melting point only
Explanation: Saturation level strongly controls reactivity.
Hydrocarbon logic
125. A quick NEET route in hydrocarbons is to classify the substrate as alkane, alkene, alkyne, or aromatic, then recall the chapter’s:
- A. signature reaction pattern (Correct)
- B. molar conductivity
- C. lattice enthalpy
- D. electrode potential
Explanation: Each family has a characteristic style of reactivity.

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