${{\rm{C}}_2}-{{\rm{C}}_3}$ bond length in but-1,3-diene is:

$1.34\mathop {\rm A}\limits^ \circ $

$1.46\mathop {\rm A}\limits^ \circ $

$1.20\mathop {\rm A}\limits^ \circ $

$1.39\mathop {\rm A}\limits^ \circ $

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NEET • CHEMISTRY • HYDROCARBONS

Hydrocarbons practice · Mixed difficulty

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121 Hard

121 of 229

Application +4 | -1

3-Phenylpropene on reaction with

HBr

gives (as a major product) :

View answer and explanation

Correct option: B

{C_6}{H_5}CH(Br)C{H_2}C{H_3}

Ethylene differs from the other three because it is an aliphatic alkene, while naphthalene, toluene, and xylene are aromatic hydrocarbons.

122 Easy

122 of 229

Remembering +4 | -1

Which of the following is not a mixture of hydrocarbons?

View answer and explanation

Correct option: C

Vegetable oils

Option C (Vegetable oils) is correct because vegetable oils are triglycerides, which are esters of glycerol and fatty acids, not mixtures of hydrocarbons.

123 Easy

123 of 229

Analyzing +4 | -1

Which of the following compounds cannot be prepared singly by the Wurtz reaction?

View answer and explanation

Correct option: B

{\left( {\mathrm{C}{\mathrm{H}_3}} \right)_2}\mathrm{CHC}{\mathrm{H}_3}

Option B (

{\left( {\mathrm{C}{\mathrm{H}_3}} \right)_2}\mathrm{CHC}{\mathrm{H}_3}

) is correct because Wurtz reaction can produce symmetrical alkanes in good yield, but unsymmetrical alkanes are difficult to prepare singly due to side products.

124 Medium

124 of 229

Understanding +4 | -1

Aromatisation of n-neptane by passing over heated

A{l_2}{O_3}

and

C{r_2}{O_3}

at 773

K

gives

View answer and explanation

Correct option: B

toluene

Option B (toluene) is correct because n-heptane undergoes aromatization to form toluene.

125 Easy

125 of 229

Application +4 | -1

When sodium propionate is heated with soda-lime, the product formed is

View answer and explanation

Correct option: B

Ethane

Option B (Ethane) is correct because the decarboxylation of sodium propionate with soda-lime removes a carbon atom, resulting in ethane.

126 Medium

126 of 229

Understanding +4 | -1

C{H_3} - C{H_3} + HN{O_3}\xrightarrow{{675K}}

View answer and explanation

Correct option: A

C{H_3} - C{H_3} + N{O_2}

Option B (

C{H_3}C{H_2}N{O_2} + C{H_3}N{O_2}

) is correct because the reaction of ethane with nitric acid at high temperatures leads to the formation of nitroalkanes through a free radical mechanism.

127 Easy

127 of 229

Application +4 | -1

When butene-1 is mixed with HBr, the major reaction product is:

View answer and explanation

Correct option: C

2-bromobutane

Option C (2-bromobutane) is the major product because, according to Markovnikov's rule, the bromine atom adds to the carbon with more alkyl substituents.

128 Medium

128 of 229

Analyzing +4 | -1

Compound X of molecular formula

{C_4}{H_6}

takes up one equivalent of hydrogen in presence of Pt to form another compound Y which on ozonolysis give only ethanoic acid. The compound X can be

View answer and explanation

Correct option: D

All of three

Option D (All of three) is correct because all three compounds,

C{H_2} = CH - CH = C{H_2}

C{H_2} = C = CHC{H_3}

, and

C{H_3}C \equiv CC{H_3}

, can be hydrogenated to form butane, which upon ozonolysis yields ethanoic acid.

129 Easy

129 of 229

Understanding +4 | -1

Arrange the following molecules in the correct order of decreasing

C - C

bond length

View answer and explanation

Correct option: A

{C_2}{H_6} > {C_6}{H_6} > {C_2}{H_4} > {C_2}{H_2}

Option B (

{C_2}{H_6} > {C_2}{H_4} > {C_6}{H_6} > {C_2}{H_2}

) is correct because bond length decreases with increasing bond order: single bond > benzene (intermediate) > double bond > triple bond.

130 Medium

130 of 229

Remembering +4 | -1

The most stable conformational isomer of cyclohexane is:

View answer and explanation

Correct option: A

Chair form

Option A (Chair form) is correct because the chair conformation of cyclohexane is the most stable due to minimal steric and torsional strain.

131 Hard

131 of 229

Understanding +4 | -1

S-I: Friedal Crafts Acylation of benzene with acetic anhydride in presence of anhydrous

{AlCl}_3

yields acetophenone and not poly substituted products.
S-II: It is due to stearic hindrance of bulky actyl group

C{H_3} - \mathop {{\text{ }}C}\limits^{\begin{array}{cccccccccccccccccccc} O \\ \parallel \end{array}}-

and also, it is a deactivating group.

View answer and explanation

Correct option: A

S-I

\&

S-II are true

S-I

\& S-II are true because Friedel-Crafts acylation yields acetophenone due to deactivation and steric hindrance of the acyl group, preventing polysubstitution.

132 Medium

132 of 229

Application +4 | -1

Both

C{H_4}

and

{C_2}{H_6}

can be prepared in one step by the reaction of

View answer and explanation

Correct option: A

C{H_3}Br

The correct answer is

CH_3Br

because it can undergo a Wurtz reaction to form both methane and ethane.

133 Medium

133 of 229

Remembering +4 | -1

S-I: Benzene reacts with

{Cl}_2

in presence of sunlight to form benzene hexachloride (BHC).
S-II: BHC or Gammaxane or 666 is used as insecticide.

View answer and explanation

Correct option: A

S-I

\&

S-II are true

Option A (S-I & S-II are true) is correct because both statements are factually accurate regarding the formation and use of benzene hexachloride (BHC).

134 Medium

134 of 229

Remembering +4 | -1

The neutral wax called Ozokerite found near petroleum well is a mixture of:

View answer and explanation

Correct option: B

Solid hydrocarbons

Option B (Solid hydrocarbons) is correct because Ozokerite is a naturally occurring mineral wax composed of solid hydrocarbons.

135 Easy

135 of 229

Application +4 | -1

When HCI gas is passed through propene in the presence of benzoyl peroxide, it gives:

View answer and explanation

Correct option: B

2-chloropropane

The correct answer is 2-chloropropane because in the presence of peroxide, HCl undergoes Markovnikov addition to propene.

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136 Easy

136 of 229

Remembering +4 | -1

Which of the following is correct formula of Gammaxane

View answer and explanation

Correct option: C

{C_6}{H_6}C{l_6}

Option C (

{C_6}{H_6}C{l_6}

) is correct because it represents the molecular formula of Gammaxane, also known as benzene hexachloride (BHC).

137 Medium

137 of 229

Analyzing +4 | -1

A hydrocarbon gives two moles of an aldehyde of molar mass 44 on reductive ozonolysis. IUPAC name of hydrocarbon is

View answer and explanation

Correct option: C

But-2-ene

Option C (But-2-ene) is correct because reductive ozonolysis of but-2-ene yields two moles of acetaldehyde (molar mass 44).

138 Medium

138 of 229

Understanding +4 | -1

But – 2 – yne is formed by reaction of

View answer and explanation

Correct option: B

C{H_3}I

with disodium acetylide

Option B (

CH_3I

with disodium acetylide) is correct because the reaction of disodium acetylide with methyl iodide results in the formation of but-2-yne through SN2 reaction.

139 Medium

139 of 229

Understanding +4 | -1

Among the following the most reactive alkene towards

HBr

View answer and explanation

Correct option: A

{\left( {C{H_3}} \right)_2}C = C{\left( {C{H_3}} \right)_2}

Option A (

{\left( {C{H_3}} \right)_2}C = C{\left( {C{H_3}} \right)_2}

) is correct because the more substituted the alkene, the more stable the carbocation intermediate formed during the addition of HBr, and thus the more reactive the alkene.

140 Hard

140 of 229

Understanding +4 | -1

S-I: Carbon black is obtained by the incomplete combustion of

\mathrm{CH}_4

S-II:

\mathrm{KMnO}_4

oxidises alkanes containing tertiary hydrogen

View answer and explanation

Correct option: A

Both S-I

\&

S-II are correct

Both statements are correct. Carbon black is indeed produced by incomplete combustion of methane, and KMnO4 can oxidize alkanes containing tertiary hydrogens.

141 Medium

141 of 229

Understanding +4 | -1

{\mathrm{C}_2}-{\mathrm{C}_3}

bond length in but-1,3-diene is:

View answer and explanation

Correct option: D

1.34\mathop \mathrm{A}\limits^ \circ

Option D (

1.34\mathop \mathrm{A}\limits^ \circ

) is correct because the C2-C3 bond in but-1,3-diene has partial double bond character due to resonance, resulting in a bond length shorter than a typical single bond.

142 Medium

142 of 229

Remembering +4 | -1

Conformation of ethane in which hydrogen atoms attached to two carbon atoms are closest to each other is known as

View answer and explanation

Correct option: A

eclipsed

Option A (eclipsed) is correct because it describes the conformation where hydrogen atoms on adjacent carbons are closest to each other.

143 Easy

143 of 229

Analyzing +4 | -1

Which isomeric dibromotoluene is most difficult to make from toluene?

View answer and explanation

Correct option: C

3, 5

Option C (3, 5) is correct because introducing two substituents at the meta positions (3,5) with respect to the methyl group on toluene is difficult due to the directing effect of the methyl group.

144 Easy

144 of 229

Analyzing +4 | -1

Which of the following differs with the other three?

View answer and explanation

Correct option: B

Ethylene

3,5-dibromotoluene is most difficult to make from toluene because the methyl group is ortho/para directing, and it is difficult to direct two bromines to the meta positions.

145 Easy

145 of 229

Application +4 | -1

A gas formed by the action of alcoholic

KOH

on ethyl iodide, decolourises alkaline

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

. The gas is

View answer and explanation

Correct option: D

{\mathrm{C}_2}{\mathrm{H}_4}

Option D (

{\mathrm{C}_2}{\mathrm{H}_4}

) is correct because the gas formed is ethene, which has a double bond and can decolourise alkaline

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

146 Hard

146 of 229

Application +4 | -1

Which alkene on ozonolysis give

{CH}_3 {CH}_2 {CHO}

and

{CH}_3 {CHO}

View answer and explanation

Correct option: B

2-pentene

Option B (2-pentene) is correct because ozonolysis of 2-pentene yields propanal (

{CH}_3 {CH}_2 {CHO}

) and acetaldehyde (

{CH}_3 {CHO}

147 Easy

147 of 229

Remembering +4 | -1

Thermal decomposition of alkanes in the absence of air is called

View answer and explanation

Correct option: A

Cracking

Option A (Cracking) is correct because thermal decomposition of alkanes in the absence of air is specifically called cracking, breaking larger molecules into smaller ones.

148 Easy

148 of 229

Analyzing +4 | -1

Which of the following statement is false?

View answer and explanation

Correct option: B

Acetylene molecule has three ‘pi’

\left( \pi \right)

bonds and three sigma bonds

The correct answer is Acetylene molecule has three ‘pi’

\left( \pi \right)

bonds and three sigma bonds because acetylene has 3 sigma and 2 pi bonds.

149 Medium

149 of 229

Remembering +4 | -1

Natural gas is a mixture of:

View answer and explanation

Correct option: A

{CH}_4+{C}_2 {H}_6+{C}_3 {H}_8

Option A (

{CH}_4+{C}_2 {H}_6+{C}_3 {H}_8

) is correct because natural gas is primarily composed of methane, ethane, and propane.

150 Easy

150 of 229

Remembering +4 | -1

Which of the following is not a petroleum product?

View answer and explanation

Correct option: C

Bees wax

Option C (Bees wax) is correct because bees wax is a natural wax produced by honeybees, while the others are derived from petroleum.

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