Hydrocarbons Multiple Choice Questions & Answers

1. Hydrocarbons are organic compounds with element ____

a) Hydrogen
b) Oxygen
c) Carbon
d) Both hydrogen and carbon

Answer: d

Explanation: These organic compounds are made up of only carbon and hydrogen and hence the name hydrocarbons.

2. Find the odd one out.

a) Aromatic
b) Alkanes
c) Alkynes
d) Alkenes

Answer: a

Explanation: Aromatic is a separate branch of hydrocarbons. Whereas the alkanes, alkenes, and alkynes are subfamilies of the branch aliphatic hydrocarbons.

3. The simplest member of organic compounds is?

a) Methanol
b) Methane
c) Formaldehyde
d) Formic acid

Answer: b

Explanation: Methane is the simplest member of alkane family and indeed the simplest of organic compounds, as all other compounds are derived by altering this compound.

4. Ethane is obtained by electrolyzing _______

a) Potassium formate
b) Potassium succinate
c) Potassium acetate
d) Potassium fumarate

Answer: b

Explanation: By electrolyzing potassium succinate (the process is generally called Kolbe’s electrolysis), ethane is obtained.

5. “Methane is a product of aerobic respiration”.

a) False
b) True

Answer: a

Explanation: Methane is the end product of anaerobic decay of plants due to the breakdown of very complicated molecules.

6. Calcium carbide on reaction with water gives?

a) Methane
b) Ethane
c) propane
d) Acetylene

Answer: d

Explanation: Calcium carbide on reaction with water gives CaC2 + H20—-> C2H2 + Ca(OH)2.

7. Name the process associated with acylation of benzene.

a) Friedel craft reaction
b) Wurtz reaction
c) Wurtz fitting reaction
d) Debey Huckel reaction

Answer: a

Explanation: The electrophilic substitution reaction that takes place between ethanoyl chloride and benzene is called as Friedel craft reaction.

8. The hydrocarbon in which all the 4 valencies of carbon are fully occupied is called as __________

a) Alkene
b) Alkyne
c) Alkane
d) Cycloalkane

Answer: c

Explanation: Alkanes , the saturated hydrocarbons are those in which the carbon atoms are bonded covalently to each other (fully occupied). Each carbon atom is tetrahedrally surrounded by H-atoms.

9. Liquid hydrocarbon is converted into gaseous hydrocarbon by ______

a) Oxidation
b) Hydrolysis
c) Cracking
d) Distillation

Answer: c

Explanation: Under cracking with high temperature, the liquid form of hydrocarbon is converted into gaseous form.

10. Chlorination of alkanes is an example of ______

a) Radical
b) Elimination
c) Free radical
d) Addition

Answer: c

Explanation: Free radical chlorination is a reaction that substitutes a chlorine for a hydrogen on an alkane.

11. When chlorine gas reacts with methane, Which of the product is formed?

a) CHCl
b) CH2Cl
c) CH3Cl
d) CH4Cl

Answer: c

Explanation: Under the influence of UV light or with a temperature of 250-400(degree) chlorine and methane react vigorously to give hydrogen chloride and chloromethane (CH3Cl).

12. The methyl chloride undergoes substitution to form _____

a) CHCl
b) CH2Cl
c) CHCl2
d) CH2Cl2

Answer: d

Explanation: Chloromethane undergoes further substitution to form hydrogen chloride and dichloromethane (CH2Cl2).

13. Methane reacts more readily with chlorine than with Fluorine.

a) True
b) False

Answer: b

Explanation: Methane reacts with chlorine but not as vigorously as with fluorine. The reactivity order is as follows: F2 > Cl2 > Br2 > I2.

14. Identify the one which is not a type of chlorination?

a) Free radical chlorination
b) Electrophobic chlorination
c) Ketone chlorination
d) Chlorine addition reaction

Answer: b

Explanation: Electrophobic is not a kind of halogenation. It is electrophilic chlorination, in which aromatic substitutions takes place.

15. Which among the following on chlorination undergoes substitution at the alkyl group?

a) Ethers
b) Hydroxyl groups
c) Carbonyl compounds
d) Carboxylic acids

Answer: a

Explanation: In the absence of sunlight, the alpha hydrogen of ethers undergoes substitution when treated with chlorine.

16. In the presence of red phosphorous, chlorine converts the fatty acids having alpha hydrogen atoms into ______

a) Halo acids
b) Alpha-halo acids
c) Alpha,alpha-dihalo acids
d) Trihalo acids

Answer: b

Explanation: The propionic acid, in the presence of Cl2/P gets converted into alpha chloro propionic acid due to the action of the halogen chlorine.

17. Chlorine in the presence of which among the following generates positively charged species?

a) Ferric chloride
b) Anhydrous ferric chloride
c) Ferrous chloride
d) Anhydrous ferrous chloride

Answer: b

Explanation: Ferric chloride is a lewis acid catalyst and in the presence of chlorine, it converts nitrobenzene into 3- chloro nitro benzene.

18. p-nitrotoluene on reaction with chlorine forms hydrogen chloride and _______

a) p-Nitrobenzyl chloride
b) o-Nitrobenzyl chloride
c) m-Nitrobenzyl chloride
d) Nitrobenzyl chloride

Answer: a

Explanation: p-Nitrotoluene reacts with chlorine in the presence of CCl4 at 80 (degree) C to form p-nitrobenzyl chloride under the conditions of photochemical initiation.

19. Chlorination of cyclobutane gives which among the following in addition to hydrogen chloride?

a) Cyclobutyl chloride
b) Cyclobutyl chlorite
c) 1-chlorobutene
d) 1,1-chlorobutene

Answer: b

Explanation: All the hydrogens of cyclobutane are equivalent and substitution of any gives the same product as that of others.

20. The step in which Cl-Cl bond homolysis occurs is called ______

a) Initiation step
b) Propagation step
c) Intermediate step
d) Termination step

Answer: a

Explanation: Each Cl atom in the initiation step has several valence electrons and is very reactive and hence it abstracts a hydrogen atom from methane and homolysis occurs.

21. The rate of the reaction is equal to the product of three factors listed below except ______

a) Collision frequency
b) Energy factor
c) Orientation factor
d) pH factor

Answer: d

Explanation: The reaction rate is given by the product of collision frequency (deals with concentration, pressure, and arrangement), energy factor (deals with distribution of kinetic energy), and orientation factor (probability factor).

22. Temperature and pressure are the only factors which affect the reaction rate.

a) True
b) False

Answer: b

Explanation: The rate of reaction is affected by three factors temperature, pressure, and concentration. All the three varies directly with the rate of the reaction.

23. The frequency of molecular collision increases if _______

a) The concentration of product increases
b) The concentration of product decreases
c) The concentration of reactant increases
d) The concentration of reactant decreases

Answer: c

Explanation: The frequency of molecular collision increases varies directly with the concentration of the reactant.

24. Identify the true statement regarding catalyst.

a) Always decreases the rate of the reaction
b) Always increases the activation energy of the reaction
c) Actually participates in the reaction
d) Changes the equilibrium concentration of the product

Answer: c

Explanation: A catalyst is a substance which when added, only alters the reaction rate temporarily and does not have a permanent effect on them and hence, only the option “Always increases the activation energy of the reaction” gives a correct info from the given choices.

25. From the choices given below, identify the activation energy of a reaction whose rate constant increases by 100 when the temperature changes from 300K to 360K.

a) 53
b) 69
c) 35
d) 42

Answer: b

Explanation: By substituting the appropriate values in the formula: (R.T1.T2)/(T1-T2)*ln(k1/k2)
we can find the value of activation energy(Ea).

26. Identify the unit of “k” in moles/L for the rate law: k[A][B]pow2.

a) L/mol/s
b) L(pow2)/mol/s
c) L(pow2)* s(pow2)/mol(pow2)
d) s

Answer: d

Explanation: Rate = k[A][B](pow2) and hence k=rate/{[A][B](pow2)}.

27. Which among the following catalyst increases the rate of the reaction?

a) Calcium carbonate
b) Calcium chloride
c) Calcium hydroxide
d) Calcium sulphate

Answer: a

Explanation: Calcium carbonate has large surface area and hence it increases the reaction rate.

28. Which is not a type of catalyst?

a) Positive catalyst
b) Negative catalyst
c) Autocatalyst
d) Homogeneous catalysis

Answer: d

Explanation: Homogeneous catalysis is a phenomenon in which the catalyst takes part in the reaction and it is not a type of catalyst.

29. What is the speed of a chemical reaction?

a) Is independent of the contact surface
b) Is constant no matter what the temperature is
c) Varies inversely with the absolute temperature
d) Is extremely rapid between the ions in aqueous solution

Answer: d

Explanation: The speed of a chemical reaction is extremely rapid between the ions in aqueous solution because there are no bonds that need to be broken.

30. The overall order for the reaction 2A+ B—> 2C with rate equation rate=k[A]^2[B] is?

a) 0
b) 1
c) 2
d) 3

Answer: d

Explanation: The order of A in this reaction is 2 and the overall reaction is a third order reaction.

31. Saturated hydrocarbons are otherwise referred as _______

a) Alkanes
b) Alkenes
c) Alkynes
d) Alkaloids

Answer: a

Explanation: Saturated hydrocarbons contain large number of hydrogen atoms in them and hence they are known as alkanes.

32. Identify the correct alkane name for the molecular formula C30H62.

a) Propdecane
b) Eicosane
c) Triacontane
d) Dodecane

Answer: c

Explanation: Triacontane is the alkane with the molecular formula C30H62 as alkanes have the general formula CnH2n+2.

33. Identify the smallest alkane which can form a ring structure (cycloalkane)?

a) Cyclomethane
b) Methane
c) Cyclopropane
d) Propane

Answer: c

Explanation: Cyclopropane is the only smallest alkane that can form a successful ring structure with C-C bond on removal of a hydrogen atom.

34. In which among the following alkane, a carbon atom is displaced so as to form a compactly structure with the resemblance of a butterfly wing?

a) Cyclopropane
b) Cyclobutane
c) Cyclopentane
d) Cyclohexane

Answer: b

Explanation: If one of the carbon atoms of cyclobutane is not displaced, then the C-C bond would be exactly at right angles to each other and they do not form a cyclic structure.

35. The first step in IUPAC nomenclature is to identify the total number of carbon atoms present in the compound.

a) True
b) False

Answer: b

Explanation: The first step is to find the number of carbon atoms present only in the main/longest chain of the compound.

36. The substituent in the chain is named by replacing the “ane” in the alkanes by _________

a) ene
b) ic
c) one
d) yl

Answer: d

Explanation: The term ene, ic and one are used for representing alkenes, carboxylic acids, and ketones respectively, hence yl is the term which is to be substituted in place on ane in the alkanes.

37. The C=C bond in the chain of the compound considered is shown by _____

a) Specifying the number of carbon atoms associated with the bond
b) Specifying the number of carbon atoms at beginning of the C=C bond
c) Specifying the number of carbon atoms at end of the C=C bond
d) Specifying the number of carbon atoms in the entire chain

Answer: b

Explanation: According to the rules of IUPAC, The C=C bond in the chain of the compound considered is shown by specifying the number of carbon atoms at beginning of the C=C bond.

38. Dienes are the name given to compounds with _______

a) Exactly a double bond
b) Exactly a triple bond
c) Exactly two double bond
d) More than two double bond

Answer: c

Explanation: Alkenes are the name given to compound with one double bond and dienes are the one given to compounds with two double bond.

39. Triple bond with two carbon atoms on either side is called ______

a) Methnyl group
b) Ethynyl group
c) Propionyl group
d) Propargyl group

Answer: b

Explanation: Triple bond with two atoms on either side are called as ethynyl group and those with one carbon on one side and two carbon on another side are called as propargyl group.

40. The substituent groups that are commonly associated with benzene ring are _______

a) Phenyl and benzyl
b) Propyl and phenyl
c) Methyl and benzyl
d) Butyl and phenyl

Answer: a

Explanation: Phenyl and benzyl are commonly associated with benzene ring due to their closely associated structure with difference in hydrogen atom.

41. Organic compounds are broadly classified as ______

a) Open chain compounds and acyclic compounds
b) Open chain compounds and linear chain compounds
c) Cyclic compounds and alicyclic compounds
d) alicyclic compounds and acyclic compounds

Answer: d

Explanation: Organic compounds are broadly classified into open chain and closed chain compounds.

42. Aliphatic compound is the other name for ______

a) Acyclic compounds
b) Alicyclic compounds
c) Ring compounds
d) Closed chain compounds

Answer: a

Explanation: Open chain compounds or acyclic compounds are otherwise called as aliphatic compounds.

43. Which among the following is not an example of Acyclic compound?

a) Acetaldehyde
b) Ethane
c) Cyclopropane
d) Isobutane

Answer: c

Explanation: Cyclopropane is a ring (cyclic) compound and hence it does not come with the examples of open chain compounds.

44. Which among the following is not an example of alicyclic compound?

a) Cyclohexane
b) Cyclohexene
c) Tetrahydrofuran
d) Acetic acid

Answer: d

Explanation: Acetic acid is a linear chain compound (acyclic) and hence it is not an example of ring compound (alicyclic).

45. Which among the following is not an aromatic compound (in specific)?

a) Naphthalene
b) Aniline
c) Pyridine
d) Tropolone

Answer: c

Explanation: Pyridine is heterocyclic aromatic compound. Whereas naphthalene and aniline are benzenoid aromatic compounds and tropolone is a non-benzenoid aromatic compound.

46. Find the odd one among the following.

a) Alicyclic compounds
b) Heterogeneous compounds
c) Branched chain compounds
d) Aromatic compounds

Answer: c

Explanation: Branched chain compound is a classification of open-chain compounds. Whereas, alicyclic, aromatic and heterogeneous compounds are sub-classifications of cyclic compounds.

47. Identify the odd one among the following.

a) Indene
b) Anthracene
c) o,m,p-xylene
d) Azulene

Answer: d

Explanation: Azulene is a non- benzenoid compound. Whereas, Indene, anthracene, and o,m,p-Xylene are examples of benzenoid aromatic compounds.

48. Organic compounds can be classified even based upon the function groups. Identify the one which is not a functional group?

a) Isocyanide
b) Isocyano
c) Carboxyl
d) Carbonyl

Answer: a

Explanation: Organic compounds can be classified even based upon the function groups. Isocyanide is a compound and it is not a functional group.

49. Which among the following is not a class of organic compound?

a) Carbonyl compound
b) Nitro compound
c) Amides
d) Electro compounds

Answer: d

Explanation: Classes of organic compounds are those which involves organic compounds such as carbon, hydrogen and oxygen. Hence, electro compounds is not a class of organic compounds.

50. Which among these is not associated with aliphatic compounds?

a) They contain (4n+2)pi electrons
b) Contain straight chain compounds
c) Contain branched chain compounds
d) Has appropriate number of H-atoms and functional groups

Answer: a

Explanation: The aromatic compounds (4n+2)pi electrons, which comes under the classification of cyclic compounds and hence they are not associated with aliphatic compounds.

51. Resonance forms are in equilibrium with each other.

a) True
b) False

Answer: b

Explanation: Resonance forms are hybrid in nature and hence it is not correct to say that they are in equilibrium with each other.

52. Identify the false statement regarding resonance.

a) As the number of charges increases, the resonance forms gets more significant
b) Zero charge of resonance is the most significant one
c) Atoms with full octet resonance form are more stable when compared with the one with unfilled octet
d) Resonance is unstable in case of unfilled octet of nitrogen atom

Answer: a

Explanation: In resonance the greater the number of charges, less stable and less significant gets the resonance form.

53. Identify the correct sequence according to electronegativity.

a) F > NH2 > CH3 >OH`
b) NH2 `> F` >CH3` > OH`
c) NH2 `> OH` > CH3` > F`
d) F` > OH` > NH2` > CH3`

Answer: d

Explanation: In the sequence ” F` > OH` > NH2` > CH3`”, F’ is the most stable one and CH3‘ is the least stable one, as the stability of the anions increases on moving towards the right of the periodic table.

54. Identify the correct sequence with respect to Inductive effects.

a) CF3`> CH2F`> CHF2`> CF3`
b) CF3`> CHF2`> CH2F`> CH3`
c) CH3`> CH2F`> CHF2`> CF3`
d) CH3`> CHF2`> CH2F`v CF3`

Answer: b

Explanation: As electron withdrawing substituent is greater in CF3, it is more stable and CH3 is the least stable one and hence the sequence.

55. Stability sequence: primary carbocation > secondary carbocation > tertiary carbocation. Is this sequence correct?

a) Yes
b) No

Answer: b

Explanation: The tertiary carbocation has the highest stability and the primary carbocation has the least stability, as it lies close to electron withdrawing group and hence the sequence is not correct.

56. Identify the incorrect statement regarding aromaticity.

a) It is the extra stability possessed by a molecule
b) p-orbitals must be planar and overlap
c) Cyclic delocalization takes place
d) It does not follow Huckel’s rule

Answer: d

Explanation: It follows Huckel’s rule, according to which a molecule must possess specific number of pi electrons within a closed ring of p-orbitals.

57. Aromatic rings do not have resonance structures.

a) False
b) True

Answer: a

Explanation: Aromatic rings have resonance structure due to cycling double bonds and all aromatic rings must have resonance but the converse need not be satisfied.

58. Select the correct statement regarding the aromatic nitrogen molecule.

a) It is not hybridized
b) It is sp hybridized
c) It is sp2 hybridized
d) It is sp3 hybridized

Answer: c

Explanation: As a result of its overall structure and electron delocalization, it becomes a sp2 hybridized, aromatic molecule.

59. Can a linear molecule have aromaticity.

a) Yes
b) No

Answer: b

Explanation: A molecule can have aromaticity if it is closed loop or ring-shaped or has p-orbitals and hence linear molecule cannot have aromaticity.

60. Select the incorrect statement.

a) A resonance may sometimes cause sp3 atoms to become sp2 hybridized
b) Delocalizing one lone pair causes aromaticity
c) One lone pair will be counted as two pi electrons according to Huckel’s equation
d) Two sigma bonds make up a double bond

Answer: d

Explanation: A double bond is one which has a sigma bond and a pi bond. Each pi bond has two pi electrons.

61. Identify the one which does not come under the organic addition reaction?

a) Hydration
b) Dehydration
c) Halogenation
d) Hydrohalogenation

Answer: b

Explanation: Dehydration comes under elimination reaction and hence it does not come under addition reaction.

62. Choose the correct one which will react faster in the SN2 nucleophilic substitution reaction?

a) CH2 – CH = CH2 = Br
b) CH2 = CH – CH2 – Br
c) CH2 = CH – CH2 = Br
d) CH = CH2 – CH2 – Br

Answer: b

Explanation: The carbocation character in the transition state causes stabilization of the resonance and hence CH2 = CH – CH2 – Br (2- bromobutane) is the one which will react faster compared to the others.

63. What will be the reactivity of chlorobenzene in an electrophilic substitution reaction with benzene?

a) Reacts very slowly than benzene
b) Reacts in the same way as benzene
c) Reacts faster than benzene
d) Does not react with benzene

Answer: a

Explanation: The rate of the reaction depends on the electron density in the ring and here in this case resonance is not favorable and the electronegativity dipole dominates. This slows down the reactivity of chlorobenzene.

64. Alcohol on refluxing with Cr2O7 gives ________

a) Ester
b) Aldehyde
c) Sugar
d) Carboxylic acid

Answer: d

Explanation: Alcohol (R-OH), when it is refluxed with Cr2O7, it forms carboxylic acid (R-COOH).

65. Alkene under high temperature and high-pressure forms _______

a) Alcohol
b) Polyalkyne
c) Polyalkane
d) Polyalkene

Answer:c

Explanation: Alkenes undergoes polymerization reaction under high temperature and pressure to form poly alkanes -(C-C)-n.

66. Identify the one which on reaction with carboxylic acid at high temperature gives Ester?

a) Ketone
b) Alcohol
c) Aldehyde
d) Sugars

Answer: b

Explanation: Alcohols on reaction with carboxylic acid at high temperature, in the presence of sulphuric acid gives Ester.

67. Select the correct statement regarding carboxylic acids.

a) They form acyl chlorides on reaction with PCl5
b) Aldehydes in the presence of H+/Cr2O7 forms carboxylic acids
c) They combine with alcohols to form esters
d) Upon polymerization, they form polymers

Answer: d

Explanation: Carboxylic acids do not undergo polymerization reaction.

68. Primary alcohols undergo what reaction to form alkenes?

a) Elimination
b) Oxidation
c) Reduction
d) Hydrolysis

Answer: a

Explanation: Upon elimination or dehydration, the primary alcohols form alkenes.

69. Carbonyl compounds especially ketones undergo reduction to form __________
a) Primary alcohols
b) Secondary alcohols
c) Alkanes
d) Alkenes

Answer: b

Explanation: Ketones in the presence of NaBH4 undergoes reduction to form secondary alcohols.

70. Primary amides get converted into primary amines by ______

a) Addition
b) Oxidation
c) Reduction
d) Acylation

Answer: b

Explanation: Primary amides upon heating in the presence of hydrogen and nickel catalyst, gets reduced to form primary amines.

71. Select the incorrect statement regarding alkanes.

a) It is otherwise known as Paraffin
b) It is an acyclic saturated hydrocarbon
c) In alkanes, C-C bonds are single
d) Alkanes have the general formula CnH2n

Answer: d

Explanation: Alkanes have the general formula CnH2n+2, i.e; they have two additional hydrogen atoms in comparison with the others.

72. Identify the simplest alkane.

a) Methane
b) Methene
c) Ethane
d) Ethene

Answer: a

Explanation: Methane, called the parent molecule, is the simplest among the alkanes and it has the simplest formula with one carbon atom.

73. Select the minimum number of carbon atoms, a molecule must possess so as to be regarded as a higher alkane.

a) 15
b) 16
c) 17
d) 18

Answer: c

Explanation: A molecule with more than 17 carbon atoms are regarded as higher alkanes such as waxes and solids.

74. Identify the incorrect statement.

a) Alkanes with repeated –CH2– units constitute a homologus series
b) They are very reactive
c) They have very less biological activity
d) Petroleum and natural gas are the main sources of alkanes

Answer: b

Explanation: Alkanes in general are not very reactive, but they are associated with functional groups which are reactive.

75. Which among the following is not an alkane isomer with 6 carbon atoms?

a) Hexane
b) 2,3-dimethylbutane
c) 2,2-dimethylbutane
d) Neopentane

Answer: d

Explanation: Neopentane is an isomer with 5 carbon atoms and hence it is not an isomer with 6 carbon atoms.

76. The other name for branched chain alkanes is ______

a) Paraffins
b) Isoparaffins
c) Neoparaffins
d) Naphthenes

Answer: b

Explanation: Linear and branched chain alkanes have difference in their physical properties and hence they are given different prefix like n- and iso-respectively.

77. Select the incorrect statement regarding the boiling points of alkanes.

a) Boiling point increases with stronger Vander Waal’s forces
b) Surface area is the only factor which determines the boiling point of alkane
c) Boiling point of straight chain alkanes is greater than that of branched chain alkanes
d) The boiling point of cycloalkanes is always higher than that of linear alkanes

Answer: b

Explanation: Number of electrons and surface area are the two factors which determine the boiling point.

78. Choose the correct statement.

a) Alkanes have poor conductivity
b) They form hydrogen bonds
c) They have good solubility in non polar solvents than polar solvents
d) Alkanes have less density than that of water

Answer: b

Explanation: They undergo polarization and hence they do not form hydrogen bonds.

79. Liquified petroleum gas is mainly composed of ______

a) Methane and ethane
b) Ethane and propane
c) Propane and butane
d) Butane and hexane

Answer: c

Explanation: At low pressure both propane and butane gets liquefied, hence they form the main components of LPG.

80. An alkane with 6 carbon atoms will have how many hydrogen atoms?

a) 11
b) 12
c) 13
d) 14

Answer: d

Explanation: From the formula CnH2n+2, if n = 6 then (2 × 6)+2 = 14. Hence 6 carbon atoms will have 14 hydrogen atom.

81. In Alkenes the Carbon atoms are connected to each other by a ______

a) Single bond
b) Double bond
c) Triple bond
d) Not connected

Answer: b

Explanation: Alkenes have at least one double bond in addition to single bond as they are unsaturated hydrocarbons.

82. Which among these is not a structural isomer of the compound C4H8?

a) But-1-ene
b) But-2-ene
c) But-3-ene
d) 2-methylpropene

Answer: c

Explanation: The compound but-3-ene have a structural formula different from the above three and hence it is not a structural isomer of C4H8.

83. Select the incorrect statement regarding alkenes.

a) In alkenes, the carbons are connected by pi bonds
b) Alkenes have almost same physical properties as that of the alkanes
c) Alkenes are less reactive than alkanes
d) Alkenes undergo polymerization reaction

Answer: c

Explanation: Alkenes are not less reactive than alkanes, indeed they are very reactive compared with them due to the presence of C = C.

84. Identify the addition reaction which is not undergone by the alkenes?

a) Mercuration
b) Oxymercuration
c) Hydroboration
d) Halogenation

Answer: a

Explanation: Alkenes do not undergo mercuration, indeed they undergo oxymercuration , a process in which an alkene is converted into an alcohol.

85. Identify the incorrect statement regarding the synthesis of alkenes.

a) Cracking of a hydrocarbon yields alkenes
b) The reactions are exothermic
c) Zeolite catalyst helps in the synthesis of alkenes
d) The synthesis of alkenes is otherwise known as reforming

Answer: b

Explanation: The reactions takes place at high temperatures and hence they are endothermic.

86. Identify the one which shows E-Z mechanism?

a) 3-methylpent-2-ene
b) 2-methylpent-2-ene
c) Methyl-3-pent-2-ene
d) 2,3-methylpentene

Answer: a

Explanation: In ‘z’ mechanism, the compounds with higher priority will be located opposite to each other of the double bond, in ‘E’ mechanism the compounds with high priority will be located in z corners and hence 3-methylpent-2-ene is the one which shows E-Z mechanism in which the priority group is CH3 and CH2CH3.

87. Which among the following is not colourless?

a) Methene
b) Ethene
c) Propene
d) Butene

Answer: b

Explanation: Methene compound does not exist according to the formula CnH2n and also due to the lack of C = C.

88. Which among the following alkenes is used in the manufacturing of plastics?

a) Butadiene
b) 1,2-butadiene
c) 1,3-butadiene
d) 2-butadiene

Answer: c

Explanation: Commonly this 1,3 butadiene is a widely used chemical in terms of a monomer as it has a very good electrical resistivity.

89. 4-chlorobut-1-ene is the name of which among the following alkenes?

a) CH2Cl-CH2=CH-CH2
b) CH2Cl-CH2-CH-CH2
c) CH2Cl=CH2-CH=CH2
d) CH2Cl-CH2-CH=CH2

Answer: d

Explanation: The structure CH2Cl-CH2-CH=CH2 has the name 4Chlorobut-1-ene according to the IUPAC naming system.

90. Ethylene on reaction with bromine forms which among the following product?

a) BrH2C-CH2Br
b) BrH2C=CH2Br
c) Br2HC=CHBr2
d) Br2HC-CHBr2

Answer: a

Explanation: The above reaction between Ethene and bromine is known as electrophilic halogenation reaction and the products usually formed are ethylene dihalides.

91. Alkynes are more reactive than alkenes.

a) False
b) True

Answer: a

Explanation: Alkynes are not as reactive when compared with the alkenes and the alkanes as they even more unsaturated when compared with them.

92. Select the incorrect statement.

a) The addition reactions occur more frequently in the alkenes than the alkynes
b) The pi system of the alkynes gets weakened when they lose the pi atoms
c) Alkynes readily undergo oligomerization
d) Alkynes do not undergo polymerization

Answer: d

Explanation: Alkynes readily undergo polymerization and form polymers such as polyacetylenes.

93. Select the incorrect statement regarding terminal alkynes.

a) Methylacetylene is an example of terminal alkynes
b) Terminal alkynes are more acidic when compared with alkenes
c) Terminal alkynes are not as acidic as alkanes
d) These have a replaceable acidic hydrogen atom

Answer: c

Explanation: Terminal alkynes are very much acidic than both alkenes and alkanes as they have a high pKa value.

94. The major alkyne, acetylene compound is produced by which among the following application on natural gas?

a) Hydrogenation
b) Partial oxidation
c) Cracking
d) Hydrohalogenation

Answer: b

Explanation: A huge quantity of acetylene is produced by partial oxidation of the natural gas.

95. Majority of the alkynes are not prepared from/by _______

a) Condensation
b) Acetylene
c) Dehydrohalogenation
d) Hydrogenation

Answer: d

Explanation: Often, alkynes are obtained from the acetylene through the condensation process and sometimes by dehydrohalogenation.

96. Alkynes cannot be prepared from ______

a) Ketones
b) Alcohols
c) Aldehydes
d) Other alkynes

Answer: b

Explanation: Only the aldehydes, ketones, and few other alkynes can give rise to a new alkyne compound.

97. The transformation into carboxylic acids of the alkynes takes place with the help of which among the following reagents?

a) Potassium chlorate
b) Potassium permanganate
c) Potassium dichromate
d) Potassium chloride

Answer: b

Explanation: The cycloaddition of the alkynes leads to the oxidative cleavage among them and hence it results in the formation of carboxylic acids.

98. Identify the incorrect statement.

a) Alkynes exists in gaseous state
b) They are soluble in water
c) They are soluble in organic solvents
d) Alkynes have a very good boiling point

Answer: b

Explanation: Alkyne molecules being non-polar, they do not dissolve in polar solvents like water.

99. Which among the following alkynes is used as a rocket fuel?

a) Ethyne
b) Propyne
c) But-1-yne
d) Pent-1-yne

Answer: b

Explanation: Propyne has many advantages and it is not as hazardous as compared to the other fuels, so they are used in rocket fuels.

100. Which among the following product is formed when ethyne undergoes hydrogenation?

a) Formaldehyde
b) Formic acid
c) Acetaldehyde
d) Acetic acid

Answer: c

Explanation: When ethyne undergoes hydrogenation in the presence of sulphuric acid, it forms ethanal.

101. Cycloalkanes are associated with the general formula called _______

a) CnH2n+2
b) CnH2(n+2)
c) CnH2n+1-r
d) CnH2(n+1-r)

Answer: d

Explanation: It is almost the same as that in the case of alkanes. Here the difference is that 2 is replaced by 1-r where r represents the number of rings in them.

102. Cycloalkanes have the same melting and boiling points as their corresponding alkanes.

a) True
b) False

Answer: b

Explanation: The melting and boiling points of the cycloalkanes are much more than the corresponding alkanes.

103. Identify the incorrect statement regarding cycloalkanes.

a) These have sp3 hybridized carbons
b) These have tetrahedral bond angles
c) Stability of the cycloalkanes varies directly with their respective size
d) These undergo nucleophilic substitution reactions

Answer: b

Explanation: Cycloalkane compounds do not have a perfect tetrahedral bond angle, instead they show a minor deviation from it which leads to destabilizing effect.

104. Identify the compound with the highest ring strain.

a) Cyclomethane
b) Cyclopropane
c) Cyclobutane
d) Cyclopentane

Answer: b

Explanation: Cyclopropane is the compound with the highest ring strain. This is because the carbon atoms are arranged in the shape of a triangle thus forming C-C-C.

105. Which among the following compounds explodes on contact with oxygen?

a) Cyclopropane
b) Cyclobutane
c) Cyclopentane
d) Cyclohexane

Answer: a

Explanation: Cyclopropane reacts very aggressively at ordinary temperatures and hence it explodes when comes in contact with oxygen.

106. Identify the incorrect statement regarding cyclobutane.

a) The carbon atoms in the cyclobutane are non-coplanar
b) These exist in nature as colourless gas
c) Cyclobutane is a commercially important compound
d) These compounds often show butterfly conformation

Answer: c

Explanation: Cyclobutane is a compound which as no commercial and medicinal importance but the complex derivative forms of them are used for a variety of purposes.

107. Identify the alicyclic hydrocarbon which is highly flammable.

a) Cycloheptane
b) Cyclopentane
c) Cyclopropane
d) Cyclooctane

Answer: b

Explanation: cyclopentane is a hydrocarbon with 5 carbon atoms and they are highly flammable.

108. Identify the incorrect statement regarding cyclohexane.

a) It is non-polar
b) It serves as an organic solvent
c) It a hydrophilic hydrocarbon
d) It is commercially used for variety of applications

Answer: c

Explanation: This compound is a hydrophobic hydrocarbon as it is non- polar by nature.

109. Identify the incorrect statement regarding cycloalkenes.

a) The bonds in them are fewer compared to those in alkenes
b) They occur in gaseous form in nature
c) These undergo polymerization
d) The conjugated double bonds in them increase their stability

Answer: b

Explanation: Cycloalkenes mostly appear in liquid state but sometimes they are even found in solid state.

110. Cycloalkene exhibits aromatic character.

a) True
b) False

Answer: b

Explanation: Cycloalkene is a compound which has carbon atoms arranged in a closed ring but they do not exhibit aromatic character.

111. Identify the incorrect statement regarding alkadiene.

a) These are acyclic acids
b) These are unsaturated hydrocarbons
c) These compounds have only one C=C bonds
d) These compounds have the general formula CnH2n-2

Answer: c

Explanation: Alkadiene compounds have a minimum of two double bonded carbon atoms but they can have more than two.

112. Alkadienes are classified into how many types?

a) 1
b) 2
c) 3
d) 4

Answer: c

Explanation: Based on the position and location of the double bonds, they are classified into three types.

113. Identify the incorrect statement regarding conjugated double bonds in alkadiene.

a) 1,3 alkadienes have conjugated double bond
b) Compounds with a double bond exhibit this type of bond
c) 1,3 pentadiene is an example for this bond
d) The conjugated dienes have properties similar to that of alkenes

Answer: b

Explanation: Compounds with alternative double and single bonds exhibit this kind of bond.

114. Identify the one which is the perfect example for Isolated double bond?

a) 1,4 pentadiene
b) 1,2 pentadiene
c) 1,3 pentadiene
d) 1,5 butadiene

Answer: a

Explanation: Only the 1,4 alkadiene compounds exhibit isolated double bonds.

115. Identify the incorrect statement regarding alkadienes.

a) Dienes show cis-trans isomerism
b) Conjugated dienes have better stability compared to other dienes
c) Dienophile supports alkadienes
d) Alkadienes also undergo hydrobromination

Answer: c

Explanation: Dienophiles attack the performance of alkadienes rather than supporting them.

116. Conjugated diene reacts with which among the following to form a cyclohexene?

a) Phenol
b) Dienophile
c) Hexane
d) Tribromo phenol

Answer: b

Explanation: Dienophile on reaction with conjugated dienes forms cyclohexene and this reaction is known as Diels-alder reaction.

117. Which among the following dienes undergo addition with the help of radical-chain mechanism?
a) Cumulated dienes
b) Isolated dienes
c) Simple dienes
d) Conjugated dienes

Answer: d

Explanation: Conjugated dienes undergoes addition reactions and the product usually formed are 1,4 dienes.

118. Identify the statement which is related to Diels-Alder reaction?

a) It is very stereospecific
b) Molecular distortion takes place
c) Cyclic dienes react very slow than the linear chain dienes
d) Addition of maleic anhydride to cyclopentadiene causes diene and dienophile to produce different products

Answer: c

Explanation: Cyclic dienes are more reactive than linear chain dienes.

119. A molecule in which more than one single bond separates two double bonds are called as ______

a) Coordinate bond
b) Isolated double bond
c) Cumulative double bond
d) Conjugated double bond

Answer: b

Explanation: As per the definition of isolation, a double bond is separated by more than a single bond.

120. Isolated dienes are similar in property to _____

a) Monoolefins
b) Diolefins
c) Triolefins
d) Tetraolefins

Answer: a

Explanation: Isolated dienes behave more like monoolefins and have properties similar to them.

121. Identify the correct statement which is related to aromatic hydrocarbon?
a) It has only sigma bonds
b) It has only pi bonds
c) It has a sigma and two pi bonds
d) It has a sigma and delocalized pi bond

Answer: d

Explanation: An aromatic hydrocarbon always has a sigma as well as a delocalized pi bond found between the carbon atoms.

122. Select the incorrect option.

a) The aromatic hydrocarbon has a pleasant aroma (smell)
b) Some of the aromatic compounds are ring-shaped
c) Aromatic hydrocarbon can be either mono or polycyclic
d) Benzene is the simplest hydrocarbon

Answer: b

Explanation: All the aromatic hydrocarbon are ring shaped as all of them are sp2 hybridized with a geometry of trigonal planar.

123. Which among the following is not a property of aromatic hydrocarbon?

a) These compounds have very good aromaticity
b) These compounds have excellent stability
c) These compounds do not undergo nucleophilic substitutions but they undergo electrophilic substitutions
d) There exists a strong ratio between carbon and hydrogen

Answer: c

Explanation: Aromatic hydrocarbons undergo both electrophilic and nucleophilic aromatic substitutions.

124. Arenes does not undergo _____

a) Dehydrogenation
b) Coupling reaction
c) Halogenation
d) Cyclo additions

Answer: a

Explanation: Arenes undergo hydrogenation reaction and form saturated ring products.

125. Which among these is not a representative arene compound?

a) Durene
b) Picric chloride
c) Aspirin
d) Mesitylene

Answer: b

Explanation: Picric acid is a representative arene compound but not picric chloride.

126. Which among these is the simplest example for polycyclic arenes?

a) Benzacephenanthrylene
b) Naphthalene
c) Pyrene
d) Dibenz-anthracene

Answer: b

Explanation: Naphthalene has fused ring of aromaticity and has the simplest structure when compared with other polycyclic aromatic hydrocarbons.

127. Arenes are polar.

a) True
b) False

Answer: b

Explanation: Arenes are insoluble in water and hence they are non polar compounds.

128. Arenes are _____

a) volatile
b) Water soluble
c) Non-carcinogenic
d) Mostly gases

Answer: a

Explanation: Arenes have a very low boiling point and hence they are volatile in nature.

129. The main sources of these arenes are _____

a) Petroleum
b) Biogas and petroleum
c) Petroleum and coal tar
d) Natural gas

Answer: c

Explanation: As these petroleum and natural gas comprise of naturally occurring compounds such as carbon and hydrogen in abundance, these serve as the main source of arenes.

130. Benzene has a stronger Vander-Waal’s force than Methylbenzene.

a) False
b) True

Answer: a

Explanation: The benzene molecule is smaller than that of the methylbenzene and hence it does not have the Vander-Waal’s forces as equal to those of methylbenzene.

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