MDCAT Hydrocarbons MCQs

This comprehensive set of MCQs on Hydrocarbons is designed to cover all essential topics required for success in the Medical and Dental College Admission Test (MDCAT). Focused on key subjects such as Alkanes, Alkenes, Alkynes, Aromatic Compounds, and Their Reactions, these MCQs are crafted to help aspiring medical and dental students build a strong foundation in the chemistry of hydrocarbons and their significance in health sciences.

Who should practice Hydrocarbons MCQs?

Students preparing for the MDCAT who wish to deepen their understanding of hydrocarbon structures, properties, and reactions, which are essential for various applications in medicine and pharmacology.
Individuals seeking to enhance their knowledge of organic compounds and their behaviors, crucial for success in biochemistry and organic chemistry courses.
University students targeting high-yield topics like hydrocarbons in biological systems and the environmental impact of organic compounds.
Anyone aiming to strengthen their foundational understanding of hydrocarbons and their implications for health, energy, and environmental sciences.
Candidates focused on developing critical thinking and analytical skills related to chemical reactions and their relevance to human health.

1. Which type of hydrocarbon contains carbon atoms arranged in a straight or branched chain?

A) Aromatic hydrocarbons
B) Closed-chain hydrocarbons
C) Open-chain hydrocarbons
D) Saturated hydrocarbons

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2. Which of the following is a characteristic of closed-chain hydrocarbons?

A) They contain only carbon and hydrogen atoms.
B) They have no double or triple bonds.
C) They are cyclic in structure.
D) They do not exhibit resonance.

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3. What is the IUPAC name for the alkane with the molecular formula C5H12?

A) Butane
B) Pentane
C) Hexane
D) Propane

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4. Which of the following is the correct IUPAC name for CH3-CH=CH-CH3?

A) Butyne
B) Butene
C) 1-Butene
D) 2-Butene

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5. Which hydrocarbon has the molecular formula C2H2?

A) Ethane
B) Ethene
C) Ethyne
D) Propane

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6. How many hydrogen atoms are in the molecular formula of alkanes?

A) 2n + 2
B) 2n – 2
C) n + 1
D) n – 1

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7. What is the structure of benzene?

A) Linear
B) Triangular
C) Planar
D) Tetrahedral

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8. Which type of reaction involves the substitution of a hydrogen atom in benzene?

A) Addition reaction
B) Elimination reaction
C) Electrophilic substitution reaction
D) Free radical substitution

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9. What is the hybridization of the carbon atoms in benzene?

A) sp
B) sp2
C) sp3
D) dsp3

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10. Which method describes the delocalization of electrons in benzene?

A) Electrophilic addition
B) Resonance
C) Hybridization
D) Induction

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11. What is the bond angle in benzene?

A) 109.5°
B) 120°
C) 180°
D) 90°

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12. Which of the following represents a characteristic reaction of benzene?

A) Addition of HBr
B) Hydrogenation
C) Electrophilic substitution
D) Halogenation

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13. What is the product of the electrophilic substitution of benzene with chlorine in the presence of FeCl3?

A) Benzene chloride
B) Chlorobenzene
C) Phenol
D) Dichlorobenzene

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14. Which resonance structure of benzene has a positive charge on a carbon atom?

A) The one with alternating double bonds
B) The one with a single bond between all carbon atoms
C) The one with a double bond and a positive charge
D) All resonance structures have no charges

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15. What type of bond is formed between carbon atoms in benzene?

A) Ionic bond
B) Polar covalent bond
C) Nonpolar covalent bond
D) Coordinate bond

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16. Which alkene has the molecular formula C4H8?

A) Butene
B) Propene
C) Pentene
D) Ethylene

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17. Which of the following statements is true about alkynes?

A) They contain only single bonds.
B) They contain at least one triple bond.
C) They are saturated hydrocarbons.
D) They are nonpolar compounds.

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18. What is the IUPAC name for the compound CH3-CH2-CH=CH2?

A) 1-Butene
B) 2-Butene
C) Propene
D) Butyne

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19. How many sigma bonds are present in the benzene molecule?

A) 6
B) 3
C) 12
D) 9

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20. In the molecular orbital treatment of benzene, how many pi electrons are involved in resonance?

A) 4
B) 6
C) 2
D) 8

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21. Which of the following compounds has a cyclic structure?

A) Butane
B) Cyclohexane
C) Pentane
D) Ethyne

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22. What is the common name for the compound C6H6?

A) Cyclohexane
B) Benzene
C) Toluene
D) Xylene

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23. Which of the following is a property of benzene?

A) High boiling point
B) Strong smell
C) High polarity
D) Aromaticity

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24. What type of hydrocarbon is represented by the formula CnH2n?

A) Alkane
B) Alkene
C) Alkyne
D) Aromatic

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25. What is the main product of the complete combustion of alkanes?

A) Water
B) Carbon dioxide
C) Carbon monoxide
D) Benzene

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26. Which of the following is the correct IUPAC name for CH3-CH2-CH2-CH3?

A) Butane
B) Butene
C) 2-Butanol
D) 3-Methylbutane

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27. What is the molecular formula of 1-pentene?

A) C5H12
B) C5H10
C) C5H8
D) C5H14

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28. Which alkene is known for its use in the polymer industry?

A) Ethylene
B) Propylene
C) Butylene
D) All of the above

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29. How does the boiling point of branched alkanes compare to straight-chain alkanes?

A) Higher
B) Lower
C) Same
D) Depends on the temperature

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30. What is the hybridization of the carbon atoms in ethylene (C2H4)?

A) sp
B) sp2
C) sp3
D) dsp2

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31. Which functional group is characteristic of alkynes?

A) Hydroxyl group
B) Carbonyl group
C) Triple bond
D) Double bond

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32. Which of the following represents the general formula for cycloalkanes?

A) CnH2n
B) CnH2n+2
C) CnH2n-2
D) CnH2n-4

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33. Which of the following hydrocarbons is not saturated?

A) Ethane
B) Butene
C) Cyclopropane
D) Octane

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34. What is the product of the reaction between benzene and nitric acid in the presence of sulfuric acid?

A) Nitrobenzene
B) Aniline
C) Benzene sulfonic acid
D) Benzaldehyde

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35. Which is a property of alkynes?

A) They are saturated hydrocarbons.
B) They contain at least one triple bond.
C) They have lower boiling points than alkenes.
D) They do not undergo addition reactions.

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36. What type of isomerism is shown by butane and isobutane?

A) Structural isomerism
B) Geometric isomerism
C) Optical isomerism
D) Conformational isomerism

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37. What is the IUPAC name for the compound with the formula CH3-CH2-C≡CH?

A) Butyne
B) 1-Butyne
C) 2-Butyne
D) Propyne

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38. Which of the following statements is true about the molecular orbital theory?

A) Electrons are considered to be localized in specific bonds.
B) It helps explain the bonding in molecules like benzene.
C) It only applies to ionic compounds.
D) It does not account for resonance structures.

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39. Which of the following compounds is an aromatic hydrocarbon?

A) Ethanol
B) Cyclohexane
C) Benzene
D) Propylene

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40. In benzene, how many pi bonds contribute to the resonance structures?

A) 1
B) 2
C) 3
D) 6

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41. Which type of reaction does not occur in benzene?

A) Electrophilic substitution
B) Nucleophilic substitution
C) Addition reaction
D) Free radical substitution

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42. Which of the following is a characteristic of open-chain hydrocarbons?

A) They are always cyclic.
B) They can be branched or unbranched.
C) They contain only double bonds.
D) They are always saturated.

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43. What is the primary product of the hydrogenation of benzene?

A) Cyclohexane
B) Toluene
C) Phenol
D) Styrene

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44. What is the molecular formula of 1-butyne?

A) C4H8
B) C4H6
C) C4H10
D) C4H12

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45. What is the type of bond formed between hydrogen and carbon in hydrocarbons?

A) Ionic bond
B) Polar covalent bond
C) Nonpolar covalent bond
D) Metallic bond

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46. Which of the following compounds is a diene?

A) Ethene
B) Butadiene
C) Propane
D) Cyclobutane

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47. What is the effect of branching on the boiling point of alkanes?

A) Increases boiling point
B) Decreases boiling point
C) No effect on boiling point
D) Makes boiling point unpredictable

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48. Which reagent is used to convert benzene to phenol?

A) Sodium hydroxide
B) Sodium bicarbonate
C) Sulfuric acid
D) Hydrochloric acid

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49. Which carbon atom is the first in the chain of the following compound: CH3-CH2-CH=CH2?

A) The first carbon in the leftmost CH3 group
B) The carbon in the double bond
C) The first carbon in the rightmost CH2 group
D) The carbon next to the double bond

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50. What type of isomerism occurs in compounds with the same molecular formula but different connectivity?

A) Geometric isomerism
B) Structural isomerism
C) Enantiomerism
D) Conformational isomerism

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51. Which of the following is a feature of aromatic compounds?

A) They have a linear structure.
B) They are highly reactive.
C) They exhibit resonance stability.
D) They contain only single bonds.

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52. What type of reaction is involved in the addition of HBr to an alkene?

A) Electrophilic substitution
B) Nucleophilic substitution
C) Electrophilic addition
D) Free radical addition

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53. Which compound is formed when benzene is treated with sulfuric acid?

A) Phenol
B) Benzene sulfonic acid
C) Nitrobenzene
D) Toluene

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54. Which of the following compounds is not an alkene?

A) Ethylene
B) Propylene
C) Butene
D) Cyclopropane

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55. What is the major product of the reaction of benzene with bromine in the presence of a catalyst?

A) Bromobenzene
B) Phenyl bromide
C) Bromoethane
D) Dibromobenzene

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56. What is the hybridization of carbon in an alkyne?

A) sp
B) sp2
C) sp3
D) dsp3

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57. Which hydrocarbon is a cyclic alkene?

A) Cyclohexene
B) Cyclopropane
C) Butylene
D) Ethane

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58. What is the molecular formula for octyne?

A) C8H14
B) C8H16
C) C8H18
D) C8H10

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59. In the context of benzene, what does the term “aromaticity” refer to?

A) Reactivity of the compound
B) Stability due to resonance
C) The presence of triple bonds
D) The solubility in water

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60. Which of the following is true regarding the structure of benzene?

A) It has alternating single and double bonds.
B) It has six equivalent carbon-carbon bonds.
C) It is a non-planar molecule.
D) It has a fixed structure with no resonance.

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61. What is the main product of the hydration of an alkene?

A) Alkane
B) Alcohol
C) Ether
D) Aldehyde

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62. Which carbon is the central atom in a cyclic compound?

A) Any carbon in the cycle
B) The carbon with the highest degree
C) The carbon with the lowest hybridization
D) None of the above

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63. Which of the following is a property of alkynes?

A) They are saturated.
B) They are more reactive than alkenes.
C) They do not undergo polymerization.
D) They are nonpolar compounds.

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64. What is the IUPAC name for CH3-CH2-CH2-CH2-CH3?

A) Pentane
B) Hexane
C) Butane
D) Heptane

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65. What is the effect of adding hydrogen to benzene?

A) It forms a saturated compound.
B) It increases aromaticity.
C) It decreases stability.
D) It does not change the compound.

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66. What is the IUPAC name for the compound with the formula CH3-CH=CH-CH2-CH3?

A) 1-Hexene
B) 2-Hexene
C) 3-Hexene
D) 1-Pentene

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67. Which of the following hydrocarbons is a branched alkane?

A) 2-Methylbutane
B) Butane
C) Hexane
D) Ethane

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68. What is the primary type of bond found in hydrocarbons?

A) Ionic bonds
B) Hydrogen bonds
C) Covalent bonds
D) Metallic bonds

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69. What is the IUPAC name for a six-membered carbon ring with alternating double bonds?

A) Cyclohexane
B) Cyclohexene
C) Benzene
D) Cycloheptane

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70. Which reagent is commonly used in the electrophilic aromatic substitution reactions?

A) HCl
B) H2SO4
C) Br2
D) Cl2

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71. Which of the following is the characteristic feature of cycloalkanes?

A) They are always unsaturated.
B) They have a closed ring structure.
C) They cannot be branched.
D) They contain only single bonds.

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72. What is the hybridization of carbon atoms in benzene?

A) sp
B) sp2
C) sp3
D) dsp2

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73. Which type of isomerism is commonly seen in alkenes?

A) Structural isomerism
B) Geometric isomerism
C) Optical isomerism
D) Conformational isomerism

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74. What is the term for a hydrocarbon with a triple bond?

A) Alkane
B) Alkene
C) Alkyne
D) Aromatic

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75. What is the main product when benzene undergoes nitration?

A) Nitrobenzene
B) Benzene sulfonic acid
C) Toluene
D) Aniline

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76. What is the molecular formula for 3-heptyne?

A) C7H12
B) C7H14
C) C7H16
D) C7H18

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77. What is the effect of adding substituents to benzene on its reactivity?

A) They do not affect reactivity.
B) They can either increase or decrease reactivity.
C) They always decrease reactivity.
D) They always increase reactivity.

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78. Which of the following is a property of alkenes?

A) They are saturated.
B) They are less reactive than alkanes.
C) They can undergo addition reactions.
D) They do not polymerize.

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79. What type of bonding is present in the molecular orbital diagram of benzene?

A) Sigma bonds only
B) Pi bonds only
C) Both sigma and pi bonds
D) Only ionic bonds

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80. What is the main product of the dehydration of alcohols?

A) Alkane
B) Alkene
C) Ether
D) Aldehyde

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81. What is the IUPAC name of the compound with the structure CH3-CH2-C≡C-CH3?

A) 1-Pentyne
B) 2-Pentyne
C) 1-Butyne
D) 2-Butyne

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82. Which reaction mechanism is common for electrophilic aromatic substitution?

A) Addition mechanism
B) Elimination mechanism
C) Rearrangement mechanism
D) Nucleophilic substitution mechanism

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83. What is the name of the resonance structure in benzene?

A) Resonance hybrid
B) Resonance contributor
C) Resonance donor
D) Resonance acceptor

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84. Which of the following compounds is a primary alcohol?

A) 2-Propanol
B) 1-Butanol
C) 2-Butanol
D) Cyclohexanol

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85. What is the hybridization of carbon atoms in alkenes?

A) sp
B) sp2
C) sp3
D) sp3d

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86. Which of the following is a feature of the electrophilic substitution reaction?

A) Involves the addition of two electrophiles
B) Produces an intermediate carbocation
C) Substitutes hydrogen atoms with electrophiles
D) All of the above

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87. What is the major product of the hydrogenation of alkenes?

A) Alkane
B) Alkyne
C) Aromatic compound
D) Alcohol

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88. What type of hydrocarbon is cyclohexane?

A) Aromatic
B) Aliphatic
C) Unsaturated
D) None of the above

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89. What is the IUPAC name for CH3-CH2-CH(CH3)-CH3?

A) 2-Methylbutane
B) 3-Methylbutane
C) 1-Methylbutane
D) 2-Pentene

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90. Which of the following reactions involves the addition of H2 to an alkene?

A) Hydrolysis
B) Hydrogenation
C) Halogenation
D) Oxidation

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91. What is the name of the mechanism in which benzene reacts with a strong electrophile?

A) Free radical substitution
B) Electrophilic addition
C) Electrophilic substitution
D) Nucleophilic substitution

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92. Which hydrocarbon is characterized by having a double bond?

A) Alkane
B) Alkene
C) Alkyne
D) Aromatic

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93. What is the major product of the reaction of benzene with nitric acid in the presence of sulfuric acid?

A) Nitrobenzene
B) Benzene sulfonic acid
C) Toluene
D) Aniline

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94. Which of the following is the correct order of increasing reactivity of hydrocarbons?

A) Alkanes < Alkenes < Alkynes
B) Alkenes < Alkanes < Alkynes
C) Alkynes < Alkenes < Alkanes
D) Alkenes < Alkynes < Alkanes

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95. What type of reaction is involved in the conversion of an alkane to an alkene?

A) Addition reaction
B) Elimination reaction
C) Substitution reaction
D) Rearrangement reaction

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96. Which of the following is a feature of aliphatic hydrocarbons?

A) They are always aromatic.
B) They can be cyclic or acyclic.
C) They contain alternating double bonds.
D) They always contain oxygen.

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97. What is the primary reason for the stability of benzene?

A) Ionic bonding
B) Resonance
C) High electronegativity of carbon
D) Presence of double bonds

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98. Which of the following hydrocarbons has the highest boiling point?

A) Ethylene
B) Propylene
C) Octane
D) Methane

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99. What is the product of the reaction of benzene with acyl chloride in the presence of a Lewis acid?

A) Aromatic ketone
B) Aromatic alcohol
C) Aromatic acid
D) Aromatic aldehyde

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100. Which of the following is not a characteristic of hydrocarbons?

A) They are composed of carbon and hydrogen.
B) They can be saturated or unsaturated.
C) They contain oxygen atoms.
D) They can be cyclic or acyclic.

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