Hydrocarbons MCQs – 4

1) During chlorination of methane to methyl chloride, the propagation step is represented by

2) Methane reacts with excess of chlorine in diffused sunlight to give the final product
a) Chloroform
b) Carbon tetrachloride
c) Methylene chloride
d) Methyl chloride.

3) An alkane with molecular weight 72 upon chlorination gives only one monochlorination product. The alkane is
a) 2-Methylbutane
b) n-Pentane
c) 2, 2-Dimethylpropane
d) All the three above.

4) Which alkane of molecular weight 72 would give three and only three different monochloro derivatives ?
a) n-Pentane
b) Isopentane
c) n-Hexane
d) Isohexane.

5) The number of monochloro derivatives of isohexane is
a) 3
b) 4
c) 5
d) 6

6) CH3CH2CH2CH3 A (2-chlorobutane )+ B(1-chlorobutane ). The approximate ratio of percentage yields of A and B formed in the above reaction is
a) 50 : 50
b) 72 : 28
c) 45 : 55
d) 60 : 40.

7) Photochemical bromination of n-butane produces
a) 1 -Bromobutane as the major product
b) 2-Bromobutane as the major product
c) Both 1-bromobutane and 2-bromobutane with equal percentage
d) Both 1-bromobutane and 2-bromobutane whose percentages depend upon temperature.

8) The major monochloro product obtained when isobutane is treated with chlorine in the presence of diffuse light in
a) Isobutyl chloride
b) n-Butyl chloride .
c) tert-Butyl chloride
d) sec-Butyl chloride.

9) The major product obtained in the photobromination of 2- methylbutane is

10) lodination of an alkane is carried out in the presence of
a) Alcohol
d) A reducing agent

11) Isomerization of an alkane may be carried out by using
a) NaOH
b) HI/P
c) Anhydrous aluminium chloride
d) Con.HCl

12) Which of the following alkanes can be easily aromatized catalytically ?
a) n-Butane
b) Isobutane
c) n-Pentane
d) n-Hexane.

13) Which of the following decolourises a hot KMnO4 solution ?

14) Which of the following is not an oxidation product of an alkane ?
a) Alcohol
b) Aldehyde
c) Carboxylic acid
d) Ether.

15) Converting n-hexane into benzene in the presence of chromium oxide on alumina support is an example of a
a) Hydrogenation reaction
b) Isomerisation reaction
c) Aromatization reaction
d) Substitution reaction.

16) When n-heptane is heated to about 773 K under high pressure and in presence of Cr2O3 deposited over AI2O3, the final product formed is
a) Cyclohexane
b) Methylcyclohexane
c) Toluene
d) Benzene

17) Which one of the following is an electrophilic addition reaction?

18) The reaction of ethene with Br2 in CCI4 gives :
a) Bromoethane
b) 1,2-Dibromoethane
c) 1,1-Dibromoethane
d) 1,1,2,2, -Tetrabromoethane.

19) The addition of halogen to an alkene involves the intermediate formation of a
a) Carbocation
b) Carbanion
c) Free radical
d) Cyclic halonium ion.

20) Which of the following products is not formed when ethylene is bubbled through an aqueous solution of bromine containing sodium chloride?
a) 1,2-Dibromoethane
b) 2-Bromo-1-chloroethane
c) 2-Bromoethanol
d) 1,2 – dichlorocthane .

21) Cyclohexene reacts with Br2 in CCI4 to form
a) cis-1, 2-Dibromocyclohexane
b) trans-1,2-Dibromocyclohexane
c) Bromocyclohexane
d) None of the above.

22) The most stable alkene among the following is

23) rule governs the addition of
a) Unsymmetrical reagents to symmetrical alkenes
b) Symmetrical reagents to unsymmetrical alkenes
c) Unsymmetrical reagents to unsymmetrical alkenes
d) Symmetrical reagents to symmetrical alkenes.

24) Which of the following reacts most readily with conc. H2SO4 ?
d) All the three above

25) Propylene is passed through cone. H2SO4 and the product thus obtained on hydrolysis with boiling water gives
a) 1-Propanol
b) 2-Propanol
c) 1-Propanal
d) 2-Propanal.

26) HBr adds to propene to form 1 -bromopropane according to
a) the peroxide effect
c) Seytzeff rule
d) All of the above

27) Addition of CI2 water (or HOCI) to propene gives
a) 1 -Chloro-2-propanol
b) 2-Chloro-1-propanol
c) 3-Chloro-1-propanol
d) 1-Chloro-1-propanol.

28) The addition of HCI to 2-methyl-2-butene mainly gives
a) 1-Chloro-2-methylbutane
b) 2-Chloro-2-methylbutane
c) 2-Chlorobutane
d) 1-Chlorobutane.

29) The peroxide effect is observed
a) Only with HBr
b) Only with HI
c) Only with HCI
d) Only with HF.

30) The addition of HCI in presence of peroxide does not follow anti- rule because the
a) HCI bond is too strong to be broken homolytically
b) Cl atom is not reactive enough to add on to a double bond
c) Cl atom combines with H atom to form HCI
d) HCI is a reducing agent.

31) The addition of HI in the presence of peroxide does not follow anti- rule because
a) HI bond is too strong to be broken homolytically
b) I atom is not reactive enough to add on a double bond
c) I combines with H to give back HI
d) HI is a reducing agent.

32) In which of the following reactions, addition does not occur according to rule ?

33) An alkene with molecular formula C4H8 upon ozonolysis gives one mole of propanone and one mole of methanal. The alkene is
a) 1-Butene
b) 2-Methylpropene
c) 2-Butene
d) 2-Methyl-2-butene.

34) Which of the following alkenes will give O = CH-CH2-CH2-CH2-CH2-CH = O when treated with ozone and then with zinc and water ?
a) 1-Hexene
b) 2-Hexene
c) 3-Hexene
d) Cyclohexene.

35) CH2 = CH-CH=CH2

36) Which of the following reagents cannot be used to distinguish between propane and propene ?

37) Cyclohexane and 1-hexene have the same molecular formula. A simple chemical test that will distinguish one from the other is
c) Bromine water
d) TollenÂ’s reagent

38) Ethylene combines with sulphur monochloride to form
a) Phosgene
b) Mustard gas
c) Methyl isocyanate (MIC)
d) Lewisite.

39) An alkene on vigorous oxidation with KMnO4 gives only acetic acid. The alkene is

40) Oxidation of 1-butene with hot KMnO4 solution produces

41) Which of the following alkenes on oxidation with hot KMnO4 will give only CH3-CO-(CH2)4-CO-CH3 ?
a) Cyclohexene
b) 1-Methylcyclohexene
c) 1, 2-Dimethylcyclohexene
d) 1, 2-Dimethylcyclopentene.

42) An alkene with the molecular formula C8H16 on oxidation with hot KMnO4 gives acetone and 3-pentanone. The structure of the alkene is

43) An alkene with the molecular formula C6H12 on oxidation with hot KMnO4 solution gives only HOOC-(CH2)4-COOH. The alkene is
a) Cyclohexene
b) 1-Methylcyclopentene
c) 1,2-Dimethylcyclobutene
d) 3-n-Propylcyclopentene.

44) Which of the following can act as both an electrophile and a nucleophile ?
a) Alkanes
b) Cycloalkanes
c) Alkenes
d) Aldehydes and ketones.

45) Which of the following will react most readily with bromine ?

46) Acetylene can be converted to acetaldehyde by the
a) Action of HOCI
d) By passing through a red hot iron tube.

47) The product/s obtained when 1-pentyne is reacted with H2O, H+, Hg2+ is/are

48) The reagent required to convert 1-butyne to 2-butanone is/are

49) Which of the following reagents on interaction would form 2, 2- dibromopropane ?
a) HC = CH + 2 HBr

50) When 1 -butyne is treated with excess of HBr, the expected product is
a) 1, 2-Dibromobutane
b) 2, 2-Dibromobutane
c) 1, 1-Dibromobutane
d) All the above.

51) 1-Butyne can be converted into 1-bromo-1-butene by reacting it with which of the following reagent ?
a) HBr

52) A mixture of acetylene and HCN in the ratio of 2 : 1 was passed through a red hot tube. The product formed is
a) Benzene
b) Pyridine
c) Pyrrole
d) Thiophene.

53) When acetylene is passed through a solution of sodium hypochlorite at 273 K in absence of air and light, the product formed is
a) 1, 1, 2, 2-Tetrachloroethane
b) Sodium acetylide
c) 1,2-Dichloroethene
d) 1, 2-Dichloroethyne.

54) Which of the following compounds on treatment with methanol in presence of potassium methoxide under pressure at 433 K will give methyl vinyl ether ?
a) Ethyne
b) Ethene
c) Propyne
d) 1, 3-Butadiene.

55) Acrylonitrile is given by the reagents
a) Acrylic acid and KCN
b) Ethyne and KCN
c) Ethyne and HOCI

56) In presence of nickel cyanide, acetylene gives
a) Benzene
b) Cyclooctatetraene
c) Cyclohexatriene
d) Cyclobutadiene.

57) Acetylene reacts with excess of hypochlorous acid to produce
a) Acetylene tetrachloride
b) Acetylene chlorohydrin
c) Acetaldehyde
d) Dichloroacetaldehyde.

58) Propyne when reacted with excess of HOCI gives
a) 1, 1, 2, 2-Tetrachloropropane
b) Propylene chlorohydrin
c) Acetone
d) 1, 1-Dichloropropanone.

59) When acetylene is passed through a solution of cuprous chloride and ammonium chloride in the presence of hydrochloric acid, it gives
a) Only vinylacetylene
b) Only divinylacetylene
c) Both vinylacetylene and di-vinylacetylene
d) None of these.

60) The gas which gives benzene on passing through a red hot iron tube is

61) Propyne when passed through a hot iron tube at 773 K produces
a) Benzene
b) Toluene
c) m-Xylene
d) Mesitylene.

62) The reaction,CH CH+NaNH2CH C Na+ +NH3 shows that the hydrogen atoms of acetylene are
a) Acidic
b) Basic
c) Neutral
d) Amphoteric.

63) Which of the following is the correct increasing order of acidity ?
a) Ethyne, ethane, ethene
b) Ethane, ethene, ethyne
c) Ethene, ethyne, ethane
d) Ethane, ethyne, ethene.

64) The order of relative acidic strength of water, ammonia and acetylene is
a) Water > ammonia > acetylene
b) Ammonia > water > acetylene
c) Water > acetylene > ammonia
d) Acetylene > water > ammonia.

65) From the following reactions,
predict which of the following orders about base strength is correct.


66) From the following reactions,
predict which of the following orders regarding acid strength is correct ?


67) The treatment of with RC s CH produces
a) RH
c) R – R

68) Which of the following reagents would you prefer to find out whether the hydrocarbon C3H4 contains one-triple bond or two-double bonds ?

69) A five carbon atom alkyne forms a sodium salt on treatment with sodamide. The alkyne is
a) only
b) only
c) only
d) Either (a) or (c).

70) A mixture of ethane, ethylene and acetylene gases is passed through a bottle containing ammoniacal silver nitrate solution. The gas coming out is
a) Ethane
b) Acetylene
c) Both ethane and ethylene
d) Original mixture.

71) A gas decolourises cold aqueous alkaline KMnO4 solution but does not give a precipitate with ammoniacal CuCI solution. The gas is
a) Methane
b) Ethane
c) Ethylene
d) Acetylene.

72) Which of the following characteristics apply to both ethene and ethyne ?
a) Explode when mixed with chlorine
b) Decolourise Baeyers reagent giving a brown precipitate
d) Form white precipitate with silver nitrate solution.

73) A metallic carbide on treatment with water gives a colourless gas which burns with a luminous flame and gives a white precipitate with ammoniacal silver nitrate. The gas is
a) Methane
b) Ethane
c) Ethylene
d) Acetylene.

74) Which of the following reagents will qualitatively distinguish between 1-butyne and 2-butyne ?

75) Which of the following reacts with an aqueous solution of [Ag(NH3)2]+ OH?

76) Alkaline KMnO4 oxidation of acetylene gives
a) Oxalic acid
b) Acetic acid
c) Formic acid
d) Glyoxal.

77) Acetylene on oxidation with chromic acid gives
a) Oxalic acid
b) Acetic acid
c) Formic acid
d) Glyoxal.

78) Alkyne, C7H12, when reacted with alkaline KMnO4 followed by acidification with HCI gives a mixture of (CH3)2CHCOOH+CH3CH2COOH. The alkyne C7H12 is
a) 3-Hexyne
b) 2-Methyl-2-hexene
c) 2-Methyl-3-hexyne
d) 3-Methyl-2-hexyne.

79) An alkyne which will react with KMnO4 to give pyruvic acid is
a) Ethyne
b) Propyne
c) 1-Butyne
d) 2-Butyne.

80) Reductive ozonolysis of acetylene gives
a) Glyoxal
b) Oxalic acid
c) Acetic acid

81) Reductive ozonolysis of propyne gives
a) 2-Oxopropanal
b) 2-Oxopropanoic acid

82) An alkyne which on ozonolysis gives two moles of acetic acid is
a) 1-Butyne
b) 2-Butyne
c) Methylacetylene
d) 3-Methyl-1-butyne.

83) Which of the following statements is correct ?
a) Alkynes are reduced less readily than alkenes
b) Alkynes are reduced more readily than alkenes
c) Both alkynes and alkenes are reduced with equal speeds
d) Alkynes cannot be reduced to alkene stage.

84) A gas which is used for the artificial ripening of fruits is
a) Methane
b) Ethane
c) Ethyne
d) Hydrogen

85) Ethylene is an unsaturated hydrocarbon which decolourises Br2/CCI4 and alkaline KMnO4 solutions. In contrast, benzene is highly unsaturated yet it does not give the above reactions. This is because
b) All the carbon-carbon bond lengths in benzene are equal
c) Benzene is stabilized by resonance
d) Benzene is a planar molecule.

86) The class of reactions most commonly given by benzene is
a) Electrophilic addition
b) Nucleophilic substitution
c) Electrophilic substitution
d) Nucleophilic addition.

87) Benzene reacts with CI2 in presence of a halogen carrier to produce
a) Benzyl chloride
b) Benzal chloride
c) Chlorobenzene
d) Benzene hexachloride.

88) Benzene reacts with excess of chlorine in sunlight to form
a) Chlorobenzene
b) p-Dichlorobenzene
c) Hexachlorobenzene
d) Benzene hexachloride.

89) The presence of electron-donating groups in the benzene ring
a) Directs the new entrant to the m-position
b) Makes further substitution difficult
c) Directs the new entrant to o- and p positions.
d) Both(b) and (c)

90) An activating group
a) activates only o- and p-positions
b) deactivates m-position
c) activates o- and p-more than m-position
d) deactivates m-more than o-and p-positions.

91) A deactivating group
a) deactivates only o-and p-positions
b) deactivates m-position
c) deactivates o-and p-more than m-position
d) deactivates m-more than o-and p-positions.

92) Amongst the following, a moderately activating group is
a) -NHR

93) Amongst the following, a weakly activating group is

94) The correct sequence for the activating power of a group in benzene is

95) The nitro group in the benzene ring is
a) Activating and o-, p-directing
b) Deactivating and m-directing
c) Deactivating and o, p-directing
d) Activating and m-directing.

96) In aniline, the – NH2 group
a) activates the benzene ring via both inductive and resonance effects
b) deactivates the benzene ring via both inductive and resonance effects
c) activates the benzene ring via the resonance effect and deactivates it via the inductive effect
d) activates the benzene ring via the inductive effect and deactivates it via the resonance effect.

97) Which of the following reacts fastest with Br2+ anhydrous AICI3 ?
a) Benzene
b) Nitrobenzene
c) Toluene
d) Anisole.

98) Benzenesulphonic acid is formed when benzene is treated with
d) All the three above.

99) The effective electrophile in aromatic sulphonation is

100) Which of the following when treated with super heated steam under pressure gives benzene ?
a) Benzenesulphonic acid
b) Benzyl chloride
c) Bromobenzene
d) Nitrobenzene.


Ans 1) c

Ans Desc 1) is the chain propagating step.

Ans 2) b

Ans Desc 2) Carbon tetrachloride is the final product, i.e., CH4 + 4 CI2 CCI4 + 4 HCI.

Ans 3) c

Ans Desc 3) Since an alkane with mol. wt. 72 (C5H12) gives only one monochloro derivative, therefore, it has only one type of H-atoms, i.e., 2, 2-dimethylpropane

Ans 4) a

Ans Desc 4) Since an alkane with mol. wt. 72 (C5H12) gives three

different monochloro derivatives, it must have three types of H-atoms, i.e., n-pentane

Ans 5) c

Ans Desc 5) Isohexane has five types of H-atoms as shown below : Therefore, it forms five monochloro derivatives.

Ans 6) b

Ans Desc 6) n-Butane has two types of H-atoms (six 1° and four 2°), therefore, it gives two monochloro derivatives, i.e., 2-chlorobutane (A) and 1-chlorobutane (B). Their relative percentage yields are :

Ans 7) b

Ans Desc 7) Photochemical bromination of n-butane will produce 2-bromobutane and 1-bromo-butane. Their relative percentage yields are :

Thus 2-bromobutane is the major product.

Ans 8) c

Ans Desc 8) 3° hydrogen is abstracted most readily and hence tert-butyl chloride is formed.

Ans 9) c

Ans Desc 9) Since the ratio of rates of abstraction of 3°, 2° and 1° H-atoms by Br is 1600 : 82 : 1 , therefore, a 3° H-atom is abstracted much more rapidly than a 2° or a 1°

H-atom. Thus, the major product is obtained by abstraction of 3° H-atom, i.e.,

Ans 10) c

Ans Desc 10) lodination of an alkane is carried out in the presence of an oxidising agent i.e. HNO3 or HIO3.

Ans 11) c

Ans Desc 11) Anhyd. AICI3 + RX (trace).

Ans 12) d

Ans Desc 12)

Ans 13) d

Ans Desc 13) A 3° H-atom is most easily oxidised. Therefore during oxidation of (CH3)3CH to (CH3)3COH the pink colour of KMnO4 solution gets discharged due to the formation of almost colourless Mn2+ ions.

(CH3)3CH + [O] (CH3)3COH

Ans 14) d


Ethers are not the oxidation products of alkanes.

Ans 15) c

Ans Desc 15) Conversion of n-hexane into benzene involves removal of six H-atoms. Therefore, this process is either called dehydrogenation or aromatization.

Ans 16) c

Ans Desc 16) First cyclization occurs to methylcyclohexane which then undergoes dehydrogenation to give toluene.

Ans 17) a

Ans Desc 17) CH2 = CH2 + Br2 BrCH2CH2Br is an example of electrophilic addition reaction.

Ans 18) b

Ans Desc 18)

Ans 19) d

Ans Desc 19)

Ans 20) d

Ans Desc 20) 1, 2-Dibromoethane, 2-bromo-1-chloroethane and 2-bromoethanol are all formed.

Ans 21) b

Ans Desc 21)

Ans 22) a

Ans Desc 22) (CH3)2C = C(CH3)2 is the most highly substituted alkene and hence is the most stable.

Ans 23) c

Ans Desc 23)

Ans 24) c

Ans Desc 24) The alkene, i.e, (CH3)2C = CH2 which gives most stable carbocation on addition of a proton is most reactive.

(CH3)2C = CH2 + H+ (CH3)3

Ans 25) b

Ans Desc 25) CH3CH = CH2 CH3-CH(OSO3H)-CH3

Ans 26) a

Ans Desc 26)

Ans 27) a

Ans Desc 27) CH3CH = CH2 + HO – Cl CH3CH(OH)CH2CI.


Ans 28) b

Ans Desc 28)

Ans 29) a

Ans Desc 29) The peroxide effect is observed only with HBr because in this case both the propagation steps are exothermic.

Ans 30) a

Ans Desc 30) The second propagating step involving the homolytic cleavage of HCI is endothermic

Ans 31) b

Ans Desc 31) The first propagating step involving the addition of Iodine to double bond is endothermic

Ans 32) b

Ans Desc 32) In the presence of peroxides, only the addition of HBr to unsymmetrical alkenes does not occur according to rule. Since alkene (b) is unsymmetrical while alkene (d) is symmetrical

Ans 33) b

Ans Desc 33)

Ans 34) d

Ans Desc 34) Since ozonolysis gives only one dialdehyde, the alkene must be cyclic, i.e., cyclohexene.

Ans 35) b

Ans Desc 35) 1, 4-Addition of H2 to 1, 3-butadiene first gives 2-butene which upon oxidative ozonolysis (O3/H2O) gives two moles of CH3CO2H.

H2/Pt O3/H2O


1 equiv. A B

Ans 36) d

Ans Desc 36) Since it neither reacts with propane nor with propene.

Ans 37) c

Ans Desc 37) Br2 in dark reacts only with 1-hexene via addition to form 1, 2-dibromohexane with simultaneous disappearance of orange colour of Br2 but not with cyclohexane since it is a saturated compound. On the other hand, Br2 in presence of sunlight will react with both cyclohexane (via substitution to form 1-bromocyclohexane) and 1-hexene (via addition as well as substitution). The other two reagents, i.e., Schiff’s reagent and ammoniacal AgNO3 solution, however, do not react either with cyclohexane or 1-hexene.

Ans 38) b

Ans Desc 38)

Ans 39) b

Ans Desc 39) Since the alkene on oxidation gives only acetic acid, therefore, the alkene must be symmetrical containing two carbon-atoms on either side of the double bond, i.e., 2-butene.



Ans 40) b

Ans Desc 40) Oxidation of 1-butene first gives a mixture of propionic acid and formic acid. Formic acid, however, gets further oxidised to CO2 and H2O.

Ans 41) c

Ans Desc 41) Since oxidation of an alkene gives only a diketone, therefore, the structure of the alkene is obtained by connecting the C-atoms of the two C = O groups,i.e.,

Ans 42) a

Ans Desc 42) Connect the C-atoms of C = O groups of acetone and 3-pentanone, the structure of

the alkene is

(CH3)2C=O+O = C(C2H5)2 (CH3)2C=C(C2H5)2.

Ans 43) a

Ans Desc 43) Since a dicarboxylic acid containing six carbon atoms is obtained, therefore, the alkene must be cyclic containing six carbon atoms, i.e., cyclohexene.

Ans 44) d

Ans Desc 44) Alkynes undergo both electrophilic and nucleophilic addition reactions.

Ans 45) c

Ans Desc 45) Alkenes are more reactive than alkynes towards electrophilic addition reactions while alkanes do not react at all. Out of CH2 = CH2 and CH3CH = CH2> CH3CH = CH2 is more reactive because the hyper conjugation effect of the CH3 group increases the electron density in the double bond thereby making it more reactive than CH2=CH2.

Ans 46) c

Ans Desc 46) CH = CH + H2O CH3-CHO.

Ans 47) a

Ans Desc 47) Self explanatory

Ans 48) c

Ans Desc 48) CH3CH2C CH CH3CH2COCH3.

Ans 49) b

Ans Desc 49) CH3C CH CH3CBr = CH2 CH3-CHBr2-CH3.

Ans 50) b

Ans Desc 50) CH3CH2C CH + 2 HBr CH3CH2 – CBr2 – CH3

1 – Butyne 2, 2-Dibromobutane

Ans 51) b

Ans Desc 51) CH3CH2C CH + HBr CH3CH2CH = CHBr.

Ans 52) b

Ans Desc 52) 2HCCH+HCN

Ans 53) d

Ans Desc 53) HCCH+2NaOCl Cl-CC-Cl+2NaOH.

Ans 54) a

Ans Desc 54) HC CH + CH3OH CH2 = CH-OCH3.

Ans 55) d

Ans Desc 55) HC CH + HCN CH2 = CHCN.

Ans 56) b

Ans Desc 56) 4 HC CH (CH = CH)4.


Ans 57) d

Ans Desc 57) HC CH + 2 HOCI [CI2CH-CH(OH)2] Cl2CH-CHO.

Ans 58) d

Ans Desc 58) CH3CH + 2 HOCI [CH3C(OH)2CHCI2] CH3COCHCl2

Ans 59) c

Ans Desc 59)

Ans 60) b

Ans Desc 60)

Ans 61) d

Ans Desc 61)

Ans 62) a

Ans Desc 62)

Ans 63) b

Ans Desc 63)

Ans 64) c

Ans Desc 64)

Ans 65) d

Ans Desc 65) It is evident from 1st Eqn. that NH is a stronger base than CH C and from 2nd Eqn. that HC C is a stronger base than OH ion. Thus option (d) is correct, i.e., OH < HC C < NH.

Ans 66) a

Ans Desc 66) It is evident from 1st reaction that HC CH is a stronger acid than NH3 and from 2nd reaction that NH3 is a stronger acid than RH. Thus, option (a) is correct, i.e., RH < NH3 < HC CH.

Ans 67) b

Ans Desc 67) + HC CR + RC MgX.

Ans 68) b

Ans Desc 68) If the hydrocarbon C3H4 contains a triple bond it must be CH3C CH. Since it being a terminal alkyne, it will react with ammoniacal AgNO3 soln. to give a white precipitate of silver propynide or with ammoniacal CuCI soln. to give a red precipitate of copper propynide.

Ans 69) d

Ans Desc 69) Since the alkyne forms a sodium salt on treatment with NaNH2, it must be a terminal alkyne, i.e., (a) CH3CH2CH2C CH or (c) (CH3)2CHC CH.

Ans 70) c

Ans Desc 70) Only acetylene reacts with ammoniacal AgNO3 soln., Therefore, the gas coming out of the bottle is a mixture of ethane and ethylene.

Ans 71) c

Ans Desc 71) Since the gas decolourises alk. KMnO4 soln., it must be unsaturated, i.e., ethylene or acetylene. Further since it does not give a ppt. with ammoniacal CuCI sol., it must be ethylene.

Ans 72) b

Ans Desc 72) Both ethene and ethyne being unsaturated decolourise Baeyers reagent giving brown ppt. of MnO2.


Ans 73) d

Ans Desc 73) Calcium carbide reacts with H2O to produce acetylene which burns with a luminous flame and gives a white ppt. with ammoniacal AgNO3 soln.

Ans 74) b

Ans Desc 74) 1-Butyne and 2-butyne both decolourise Br2/CCI4 and KMnO4 solutions. On the other hand, Cu++ neither reacts with 1-butyne nor with 2- butyne. Only Ag+ reacts with 1-butyne but not with 2-butyne.

Ans 75) c

Ans Desc 75) Self explanatory

Ans 76) a

Ans Desc 76)

Ans 77) b

Ans Desc 77)

Ans 78) c

Ans Desc 78) (CH3)2CH-C C-CH2CH3 (CH3)2CHCOOH + CH3CH2COOH.

Ans 79) b

Ans Desc 79)


Pyruvic acid

Ans 80) a

Ans Desc 80)

Ans 81) a

Ans Desc 81)


Propyne                          2-Oxopropanal

Ans 82) b

Ans Desc 82)



Ans 83) b

Ans Desc 83) Alkynes are reduced more readily than alkenes; that is why the reduction of alkynes can be stopped at the alkene stage.

Ans 84) c

Ans Desc 84)

Ans 85) c

Ans Desc 85)

Ans 86) c

Ans Desc 86)

Ans 87) c

Ans Desc 87)

Ans 88) d

Ans Desc 88)

Ans 89) c

Ans Desc 89) The presence of electron-donating groups in the benzene ring makes further substitution easier and directs the new entrant to o- and p-positions.

Ans 90) c

Ans Desc 90)

Ans 91) c

Ans Desc 91)

Ans 92) b

Ans Desc 92) NHCOCH3 is more activating than CH3 but less activating than NHR and NR2 groups.

Ans 93) c

Ans Desc 93) C6H5 group is less activating than even NHCOCH3.

Ans 94) a

Ans Desc 94) – NH2 > – NHCOCH3 > – CH3.

Ans 95) b

Ans Desc 95)

Ans 96) c

Ans Desc 96)

Ans 97) d

Ans Desc 97) CH3O-group in anisole is a much stronger electron-donating group than CH3 group in toluene while nitro group in nitrobenzene is a powerful electron-withdrawing group. Thus the electron density is maximum in anisole and hence it reacts fastest with Br2 in presence of anhyd. AICI3

Ans 98) c

Ans Desc 98)

Ans 99) d

Ans Desc 99)

Ans 100) a

Ans Desc 100) Sulphonation unlike nitration and halogenation is a reversible reaction and hence in the presence of super heated steam, benzenesulphonic acid undergoes desulphonation to give benzene.

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