Hydrocarbons Test

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Hydrocarbons Test - 75

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Weekly Quiz Competition

Question 1
1 / -0

Which of the following does not give alkane?

A
Reaction of $$CH_3I$$ with Na in ether

B
Reaction of sodium acetate with sodalime

C
Electrolysis of concentrated sodium acetate solution

D
Reaction of ethyl chloride with alco. $$KOH$$

Solution

The reaction of ethyl chloride with alcoholic KOH does not give alkane.

$$CH_3 - CH_2 - Cl + \underset{\text{(alc.)}}{KOH} \rightarrow \underset{\text{Ethene}}{CH_2 = CH_2} + KCl + H_2O$$
Question 2
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Which statement is not true concerning alkanes

A
Large number alkanes are soluble in water

B
All alkanes have a lower density than water

C
At room temperature some alkanes are liquids, some solids and some gases

D
All alkanes burn

Solution

No alkanes are not soluble in water. Water is a polar solvent and has hydrogen bonding. For any compound to be soluble in water , it should be polar or have hydrogen bonding in it.
Other then that option A, all option are correct.
Question 3
1 / -0

Benzene cannot undergo

A
Substitution

B
Addition

C
Elimination

D
Oxidation

Solution

Benzene can undergo substitution. Example: Nitration and Suphonation of Benzene.

Benzene can undergo addition reaction. Example : Bromo-Benzene

Benzene can oxidise to Phenol, Catechol, etc

So the culprit is Elimination reaction.
Benzene cannot undergo Elimination reaction.
Question 4
1 / -0

B.P. of branched chain alkanes as compared to straight chain alkanes are

A
lower

B
equal

C
higher

D
independent of the chain

Solution

As the number of branches increases, surface area decreases, due to which Van der Waal forces of attraction decreases. Hence, the boiling point also decreases.
Question 5
1 / -0

One mole of each of the following alkenes is catalytically hydrogenated. The quantity of heat evolved will be the lowest in the case of

A
1-butene

B
Trans-2-butene

C
Cis-2-butene

D
1, 3-butadiene

Solution

Heat of hydrogenation is directly related to stability alkene i.e. more is the stability of alkene smallest is the heat of hydrogenation per mole. Among the given molecules Symmetrical alkenes are highly stable. Furthermore, Trans-2-butene is more stable than cis-2-butene because in trans-2-butene the bulky methyl groups are far apart whereas in cis-2-butene the bulky groups are crowded together hence there are stearic repulsions. Hence,trans-2-butene has the lowest heat of hydrogenation per mole
Question 6
1 / -0

Necessary conditions for halogenation are

A
Cold and dark

B
Presence of halogen carrier

C
Both (a) and (b)

D
None

Solution

Option C is the correct answer .
Necessary condition for halogenation is presence of halogen carrier.

Halogenation is done in dark without any catalyst then according to free radical mechanism new halide radical will be attached to benzylic carbon. This reaction is carried out in dark so that required energy is supplied in general if it would be carried out in light chlorine free radical would be formed but in dark we use heat and supply energy. For chlorination 1kcal , bromination 16 kcal and iodination 33 kcal.
in presence of catalyst like lewis acid like $$AlCl_3$$ and $$FeCl_3$$ electrophilic substitution takes place.
Question 7
1 / -0

$$ R - CH = CH_2 + CO + H_2 \xrightarrow[{\text{High Pressure }}]{{\text{High Temp}}} \, RCH_2CH_2CHO $$
The above reaction is

A
Mendius reaction

B
Oxo process

C
Sandorn's reaction

D
Stephen's reaction

Solution

$$\text{when reaction between any alkene and water gas}$$$$(CO+H_2)$$ $$\text{is occur at high tempereture and high pressure the}$$ product will be $$\text{an aldehyde and this processis called oxo process.}$$

$$\text{thus, correct answer is B.}$$
Question 8
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Which reactions are most common in alkenes

A
Electrophilic substitution reactions

B
Nucleophilic substitution reactions

C
Electrophilic addition reactions

D
Nucleophilic addition reactions

Solution

$$\text{Electrophillic addition reactions are shown by alkenes or alkynes in these reactions attacking species is electrophiles}$$

$$CH_{3}-CH=CH_{2}+H^{+}\xrightarrow{Slow}\underset{2^{o} \,carbonium \,ion}{CH_{3}-\overset{+}{CH}-CH_{3}}$$

$$CH_{3}-\overset{+}{CH}-CH_{3}+Br^{-}\xrightarrow{Fast}CH_{3}-\!\!\!\!\!\underset{\underset{2-Bromo \,propane}{Br}}{\underset{|}{CH}}\!\!\!\!-CH_{3}$$
Question 9
1 / -0

$$ A\xleftarrow [ \Delta ]{ CU } CH_{ 3 }CH_{ 2 }OH\xrightarrow [ \Delta ]{ AL_{ 2 }O_{ 3 } } B. $$ A and B respectively are

A
Alkene, alkanal

B
Alkyne, alkanal

C
Alkanal, alkene

D
Alkene, alkyne

Solution

$$ CH_3CHO \xleftarrow [ \Delta]{Cu} CH_3CH_2OH \xrightarrow [ \Delta]{Al_2O_3 } CH_2 =CH_2 $$

Option C is correct.
Question 10
1 / -0

Point out the wrong statement in relation to the structure of benzene

A
It forms only one monosubstitution product

B
The $$C-C$$ bond distance in benzene is uniformly $$1.397\mathring{A}$$

C
It is a resonance hybrid of a number of canonical forms

D
It has three delocalised $$\pi -$$ molecular orbitals

Solution

(A) Benzene typically undergoes substitution reactions, a reaction not typical of alkenes. Benzene reacts with bromine, in the presence of iron(III) bromide as a catalyst, to give a single monosubstituted product, $$C_6H_5Br$$.This result indicates that all six hydrogen atoms of benzene are chemically equivalent.

$$\textbf{(B) }$$The six-membered ring in benzene is a perfect hexagon (all carbon-carbon bonds have an identical length of 1.40 Å). The cyclohexatriene contributors would be expected to show alternating bond lengths, the double bonds being shorter (1.34 Å) than the single bonds (1.54 Å).

$$\textbf{(C) }$$Benzene is commonly seen in Organic Chemistry and it has a resonance form. Benzene has two resonance structures, showing the placements of the bonds. Another example of resonance is ozone. Ozone is represented by two different Lewis structures.

$$\textbf{(D) }$$In benzene, the π electrons are delocalized over all six atoms of the ring. In β-carotene, the π electrons are delocalized over 22 carbon atoms.
So, The answer for ghis question is option B.

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Hydrocarbons Test - 75

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Hydrocarbons Test - 75

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Question 1

Reaction of $$CH_3I$$ with Na in ether

Reaction of sodium acetate with sodalime

Electrolysis of concentrated sodium acetate solution

Reaction of ethyl chloride with alco. $$KOH$$

Solution

Question 2

Large number alkanes are soluble in water

All alkanes have a lower density than water

At room temperature some alkanes are liquids, some solids and some gases

All alkanes burn

Solution

Question 3

Substitution

Addition

Elimination

Oxidation

Solution

Question 4

lower

equal

higher

independent of the chain

Solution

Question 5

1-butene

Trans-2-butene

Cis-2-butene

1, 3-butadiene

Solution

Question 6

Cold and dark

Presence of halogen carrier

Both (a) and (b)

None

Solution

Question 7

Mendius reaction

Oxo process

Sandorn's reaction

Stephen's reaction

Solution

Question 8

Electrophilic substitution reactions

Nucleophilic substitution reactions

Electrophilic addition reactions

Nucleophilic addition reactions

Solution

Question 9

Alkene, alkanal

Alkyne, alkanal

Alkanal, alkene

Alkene, alkyne

Solution

Question 10

It forms only one monosubstitution product

The $$C-C$$ bond distance in benzene is uniformly $$1.397\mathring{A}$$

It is a resonance hybrid of a number of canonical forms

It has three delocalised $$\pi -$$ molecular orbitals

Solution

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