Heat of hydrogenation of cyclohexene $({\rm{one}}\,\,C = C\,\,{\rm{bond}})$ is $ - 28.4\,\,k.cal.mo{l^{ - 1}}$. Hence,heat of hydrogenation of benzene $({\rm{three}}\,\,C = C\,\,{\rm{bonds}})$ should be

$ - 49.3\,\,k.cal.mo{l^{ - 1}}$

$ - 35.9\,\,k.cal.mo{l^{ - 1}}$

A hydrocarbon Xadds on one mole of hydrogen to give another hydrocarbon and decolourised bromine water. X react with ${\rm{KMn}}{{\rm{O}}_4}$ in presence of acid to give two mole of the same carboxylic acid. The structure of X is:

${\rm{C}}{{\rm{H}}_3}{\rm{C}}{{\rm{H}}_2}{\rm{CH}} = {\rm{CHC}}{{\rm{H}}_2}{\rm{C}}{{\rm{H}}_3}$

${\rm{C}}{{\rm{H}}_3}{\rm{CH}} = {\rm{CHC}}{{\rm{H}}_2}{\rm{C}}{{\rm{H}}_2}{\rm{C}}{{\rm{H}}_3}$

${\rm{C}}{{\rm{H}}_3}{\rm{C}}{{\rm{H}}_2}{\rm{C}}{{\rm{H}}_2}-{\rm{CH}} = {\rm{CHC}}{{\rm{H}}_3}$

${\rm{C}}{{\rm{H}}_2} = {\rm{CH}}-{\rm{C}}{{\rm{H}}_2}{\rm{C}}{{\rm{H}}_2}{\rm{C}}{{\rm{H}}_3}$

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NEET • CHEMISTRY • HYDROCARBONS

Hydrocarbons practice · Mixed difficulty

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Showing 61-90 of 229 questions

61 Hard

61 of 229

Remembering +4 | -1

Which of the following is carcinogenic hydrocarbon

View answer and explanation

Correct option: D

All of these

Option D (All of these) is correct because 1,2-Benzanthracene, 1,2-Benzpyrene, and 3-Methylcholanthrene are all known carcinogenic hydrocarbons.

62 Medium

62 of 229

Analyzing +4 | -1

One mole of a symmetrical alkene on ozonolysis gives two moles of an aldehyde having a molecular mass of 44 u. The alkene is

View answer and explanation

Correct option: C

2-butene

Option C (2-butene) is correct because ozonolysis of 2-butene yields two moles of acetaldehyde (molecular mass 44 u).

63 Medium

63 of 229

Remembering +4 | -1

Which of the following fuel cause the least pollution?

View answer and explanation

Correct option: D

LPG

Option D (LPG) is correct because LPG (Liquefied Petroleum Gas) generally produces less pollution compared to petrol, CNG, and kerosene when burned.

64 Easy

64 of 229

Analyzing +4 | -1

Correct statement about 1,3-dibutene

View answer and explanation

Correct option: D

All of the above

Option D (All of the above) is correct because 1,3-dibutene has conjugated double bonds, reacts with HBr, and can form a polymer.

65 Hard

65 of 229

Understanding +4 | -1

Which of the following statement(s) is/are correct regarding rotation around internuclear axis of

\mathrm{C}-\mathrm{C}

bond?

I. Rotation produces rotamers.

II. Magnitude of torsional strain depends upon the angle of rotation about

\mathrm{C}-\mathrm{C}

bond.

III. Repulsive interaction between adjacent bond is termed as torsional strain.

IV. Ethane has only four conformational isomers.
Choose the correct option.

View answer and explanation

Correct option: B

I, II and III

Option B (I, II and III) is correct because rotation around the internuclear axis of a C-C bond produces rotamers, the magnitude of torsional strain depends on the angle of rotation, and repulsive interactions between adjacent bonds are termed torsional strain.

66 Easy

66 of 229

Application +4 | -1

Hydration of but-2-ene gives

View answer and explanation

Correct option: A

C{H_3}C{H_2}\mathop C\limits_{\mathop |\limits_{OH} } HC{H_3}

Option A (

C{H_3}C{H_2}\mathop C\limits_{\mathop |\limits_{OH} } HC{H_3}

) is correct because hydration of but-2-ene in the presence of an acid catalyst follows Markovnikov's rule, leading to the formation of butan-2-ol.

67 Easy

67 of 229

Remembering +4 | -1

The number of carbon atoms in hydrocarbons of kerosene is in the range of:

View answer and explanation

Correct option: B

{\mathrm{C}_{12}}-{\mathrm{C}_{16}}

Option B (

{\mathrm{C}_{12}}-{\mathrm{C}_{16}}

) is correct because kerosene typically contains hydrocarbons with carbon chain lengths ranging from C12 to C16.

68 Easy

68 of 229

Analyzing +4 | -1

Assertion (A) Friedel-Crafts reaction benzene with n-propyl chloride onheating produce isopropyl benzene

Reason (R) Benzene undergoes electrophilic substitution easily.

View answer and explanation

Correct option: B

If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.

Option B (If both Assertion and Reason are true but Reason is not the correct explanation of Assertion) is correct because while both statements are true, the ease of electrophilic substitution doesn't directly explain why n-propyl chloride rearranges to isopropyl chloride.

69 Hard

69 of 229

Application +4 | -1

Heat of hydrogenation of cyclohexene

(\mathrm{one}\,\,C = C\,\,\mathrm{bond})

- 28.4\,\,k.cal.mo{l^{ - 1}}

. Hence,heat of hydrogenation of benzene

(\mathrm{three}\,\,C = C\,\,\mathrm{bonds})

should be

View answer and explanation

Correct option: A

- 85.2\,\,k.cal.mo{l^{ - 1}}

Option A is correct because the addition of HBr to 3-phenylpropene follows Markownikoff's rule, and also considers the stability of the carbocation intermediate. The more stable carbocation is benzylic and secondary, leading to the major product.

70 Easy

70 of 229

Remembering +4 | -1

Position of double bond in alkenes is identified by

View answer and explanation

Correct option: A

Ozonolysis

Option A (Ozonolysis) is correct because ozonolysis cleaves the double bond and the products formed can be used to determine the position of the double bond.

71 Easy

71 of 229

Understanding +4 | -1

Ca{C_2} + {H_2}O \to A\xrightarrow[{{H_2}S{O_4}}]{{HgS{O_4}}}B,

Identify

A

and

B

View answer and explanation

Correct option: A

{C_2}{H_2}\,\,and\,\,C{H_3}CHO

Option A (

{C_2}{H_2}\,\,and\,\,C{H_3}CHO

) is correct because calcium carbide reacts with water to form ethyne, which then undergoes hydration to form ethanal.

72 Medium

72 of 229

Application +4 | -1

The number of possible isomers of alkane with formula

{\mathrm{C}_6}{\mathrm{H}_{14}}

is:

View answer and explanation

Correct option: D

Option D (5) is correct because there are five structural isomers of the alkane with the formula C6H14.

73 Hard

73 of 229

Analyzing +4 | -1

Which will give cyclooctyne when treated with base?

View answer and explanation

Correct option: C

1,1-dibromocyclooctane

Option C is correct because 1,1-dibromocyclooctane can undergo two successive dehydrohalogenation reactions in the presence of a strong base to form cyclooctyne. The geminal dibromide is necessary for the elimination to form the cyclic alkyne.

74 Easy

74 of 229

Remembering +4 | -1

The treatment of calcium carbides with water gives

View answer and explanation

Correct option: B

acetylene

Option B (acetylene) is correct because calcium carbide (

CaC_2

) reacts with water to produce acetylene (

C_2H_2

75 Medium

75 of 229

Understanding +4 | -1

By heating tetraethyl ammonium hydroxide, the product formed are:

View answer and explanation

Correct option: D

All of these

Option D (All of these) is correct because heating tetraethyl ammonium hydroxide results in Hofmann elimination, producing ethene, triethylamine, and water.

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76 Easy

76 of 229

Understanding +4 | -1

Hydration of ethyne to ethanol takes place through the formation of

View answer and explanation

Correct option: B

C{H_2} = CHOH

Option B (

C{H_2} = CHOH

) is correct because the hydration of ethyne initially forms vinyl alcohol (

C{H_2} = CHOH

), which then tautomerizes to acetaldehyde.

77 Easy

77 of 229

Application +4 | -1

\mathrm{C}{\mathrm{H}_3}-\mathrm{C} \equiv \mathrm{CH}

reacts with

HCI

to give:

View answer and explanation

Correct option: A

2,2-dichloropropane

Option A (2,2-dichloropropane) is correct because the addition of HCl to propyne follows Markovnikov's rule, leading to the formation of 2-chloropropene, which then reacts with another molecule of HCl to give 2,2-dichloropropane.

78 Medium

78 of 229

Understanding +4 | -1

Which of the following will not give white ppt with ammoniacal silver nitrate

View answer and explanation

Correct option: B

2 - butyne

Option B (2 - butyne) is correct because terminal alkynes (alkynes with a hydrogen atom attached to the sp-hybridized carbon) react with ammoniacal silver nitrate to form a white precipitate, while internal alkynes do not.

79 Medium

79 of 229

Analyzing +4 | -1

Which of the following will not produce ethane

View answer and explanation

Correct option: B

reduction of

C{H_3}COC{H_3}

with

HI/{P_4}

Option B (Reduction of

\mathrm{C}{\mathrm{H}_3}\mathrm{COC}{\mathrm{H}_3}

with HI and red P) is correct because the reduction of acetone with HI and red P yields propane, not ethane.

80 Hard

80 of 229

Understanding +4 | -1

S-I: Alkynes are more reactive than alkenes towards catalytic hydrogenation
S-II: Alkynes are less reactive towards electrophilic reaction than alkenes.

View answer and explanation

Correct option: A

S-I

\&

S-II are true

Option A (S-I & S-II are true) is correct because alkynes are more reactive than alkenes towards catalytic hydrogenation, but less reactive towards electrophilic reactions.

81 Hard

81 of 229

Understanding +4 | -1

The reactants involved in general combustion equation for any alkane is represented as

View answer and explanation

Correct option: D

{C}_n {H}_{2 n+2}+\left(\frac{3 n+1}{2}\right) {O}_2

Option D (

{C}_n {H}_{2 n+2}+(\frac{3 n+1}{2}) {O}_2

) is correct because it represents the balanced general combustion equation for any alkane, where the coefficients are correctly balanced to ensure the conservation of mass.

82 Easy

82 of 229

Understanding +4 | -1

Which of the following is unsymmetrical alkene?

View answer and explanation

Correct option: D

All of these

Option D (All of these) is correct because 1-butene, 2-hexene, and 1-pentene all have different groups attached to the carbon atoms of the double bond, making them unsymmetrical.

83 Medium

83 of 229

Remembering +4 | -1

When two halogen atoms are attached to two adjacent carbon atoms, the dihaloalkane is called :

View answer and explanation

Correct option: C

Alkylene dihalide

Option C (Alkylene dihalide) is correct because alkylene dihalides have two halogen atoms attached to two adjacent carbon atoms.

84 Hard

84 of 229

Remembering +4 | -1

Angle strain in cyclopropane is

View answer and explanation

Correct option: A

24^\circ 44'

Option A (

24^\circ 44'

) is correct because cyclopropane is a three-membered ring with bond angles of 60°, leading to a significant angle strain compared to the ideal tetrahedral angle of 109.5°.

85 Easy

85 of 229

Analyzing +4 | -1

A hydrocarbon Xadds on one mole of hydrogen to give another hydrocarbon and decolourised bromine water. X react with

\mathrm{KMn}{\mathrm{O}_4}

in presence of acid to give two mole of the same carboxylic acid. The structure of X is:

View answer and explanation

Correct option: B

\mathrm{C}{\mathrm{H}_3}\mathrm{C}{\mathrm{H}_2}\mathrm{CH} = \mathrm{CHC}{\mathrm{H}_2}\mathrm{C}{\mathrm{H}_3}

Option B (

\mathrm{C}{\mathrm{H}_3}\mathrm{C}{\mathrm{H}_2}\mathrm{CH} = \mathrm{CHC}{\mathrm{H}_2}\mathrm{C}{\mathrm{H}_3}

) is correct because it adds one mole of hydrogen and gives two moles of the same carboxylic acid upon reaction with

\mathrm{KMn}{\mathrm{O}_4}

86 Medium

86 of 229

Understanding +4 | -1

The relative rates of reaction of alkene with

B{r_2}/C{H_3}OH

are in order

View answer and explanation

Correct option: A

ethene < 1 – butene < trans but–2-ene

Option A (ethene < 1 – butene < trans but–2-ene) is correct because the rate of reaction with

Br_2/CH_3OH

increases with increasing alkyl substitution on the alkene.

87 Easy

87 of 229

Understanding +4 | -1

Alkyl halides have higher boiling points than alkanes (having same number of carbon atoms) because of

View answer and explanation

Correct option: A

dipole – dipole interaction

Option A (dipole – dipole interaction) is correct because alkyl halides are polar molecules due to the electronegativity difference between the halogen and carbon atoms, leading to dipole-dipole interactions.

88 Medium

88 of 229

Application +4 | -1

Major product of the given reaction is

C{H_3}CH = C{H_2}

View answer and explanation

Correct option: B

C{H_3}CH\left( {OH} \right)C{H_2}\left( {OH} \right)

Option B (

C{H_3}CH(OH)C{H_2}(OH)

) is correct because the reaction of propene with

KMnO_4

results in syn-dihydroxylation of the double bond, forming a vicinal diol.

89 Medium

89 of 229

Analyzing +4 | -1

Which of the following compounds are not arranged on order of decreasing reactivity towards electrophilic substitution?

View answer and explanation

Correct option: D

Benzoic acid> phenol>

n

- propyl benzene

Option D (Benzoic acid> phenol>

n

- propyl benzene) is correct because it incorrectly orders the reactivity; electron-donating groups increase reactivity, while electron-withdrawing groups decrease it.

90 Medium

90 of 229

Application +4 | -1

In the following reaction, the product ‘

R

’ is

Ca{C_2}\xrightarrow{{{H_2}O}}P\xrightarrow[{\mathrm{tube}}]{{\mathrm{Hot,}\,\mathrm{iron}}}Q\xrightarrow{{C{H_3}Cl}}R

View answer and explanation

Correct option: C

toluene

Benzoic acid is the correct answer because toluene (formed by Friedel-Crafts alkylation of benzene) is oxidized by

KMn{O_4}

to form benzoic acid.

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