Test: 35 Year JEE Previous Year Questions: Hydrocarbons


24 Questions MCQ Test Class 11 Chemistry 35 Years JEE Mains &Advance Past yr Paper | Test: 35 Year JEE Previous Year Questions: Hydrocarbons


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QUESTION: 1

Which of these will not react with acetylene? [2002]

Solution:

Acetylene reacts with the other three as:

QUESTION: 2

What is the product when acetylene reacts with hypochlorous acid? [2002]

Solution:

QUESTION: 3

On mixing a certain alkane with chlorine and irradiating it with ultraviolet light, it forms only one monochloroalkane.This alkane could be [2003]

Solution:

In neopentane all the H atoms are same (1º).

QUESTION: 4

2-Methylbutane on reacting with bromine in the presence of sunlight gives mainly [2005]

Solution:

 

Ease of replacement of H-atom 3° > 2° > 1°.

QUESTION: 5

Butene-1 may be converted to butane by reaction with

Solution:

Alkenes combine with hydrogen under  pressure and in presence of a catalyst (Ni, Pt or Pd) and form alkanes.

QUESTION: 6

Reaction of one molecule of HBr with one molecule of 1, 3-butadiene at 40°C gives predominantly [2005]

Solution:

                                                

QUESTION: 7

Of the five isomeric hexanes, the isomer which can give two monochlorinated compounds is [2005]

Solution:

Since it contains only two  types of H-atoms hence it will give only two mono  chlorinated compounds viz. 

 and 

QUESTION: 8

Acid catalyzed hydration of alkenes except ethene leads to the formation of

Solution:

Water adds directly to the more reactive alkene in presence of a  strongly acidic catalyst forming alcohols.
Addition occurs according to Markonikov’s rule.

NOTE : Addition follows Markownikoff’s rule.

QUESTION: 9

Which types of isomerism is shown by 2, 3-dichlorobutane? [2005]

Solution:

2, 3-dichloro butane will exhibit optical isomerism due to the presence of two asymmetric carbon atom.

QUESTION: 10

The compound formed as a result of oxidation of ethyl benzene by KMnO4 is [2007]

Solution:

When alkyl benzene are oxidised with alkaline KMnO4, (strong oxidising agent) the entire alkyl group is oxidised to –COOH group regardless of length of side chain.

QUESTION: 11

Which of the following reactions will yield 2, 2-dibromopropane? [2007]

Solution:

The reaction follows Markownikoff rule which states that when unsymmetrical reagent adds across unsymmetrical double or triple bond the negative part adds to carbon atom having lesser number of hydrogen atoms.

QUESTION: 12

The reaction of toluene with Cl2 in presence of FeCl3 gives predominantly [2007]

Solution:

FeCl3 is Lewis acid. In presence of FeCl3 side chain hydrogen atoms of toluene are substituted.

QUESTION: 13

Toluene is nitrated and the resulting product is reduced with tin and hydrochloric acid. The product so obtained is diazotised and then heated wth cuprous bromide. The reaction mixture so formed contans [2008]

Solution:

NOTE : ​group whichis o-, p- directing group so on nitration of toluene the – NO2 group will occupy o-, p- positions.

on reduction with Sn/HCl they will form corresponding anilines in which –NO2 group changes to –NH2. The mixture now contains

anilines when diazotized and then treated with CuBr forms o-, p- bromotoluenes.

QUESTION: 14

In the following sequence of reactions, the alkene affords the compound ‘B’

The compound B is [2008] 

Solution:

Completing the sequence of given reactions,

Thus ‘B’ is CH3CHO Hence (d) is correct answer.

QUESTION: 15

The hydrocarbon which can react with sodium in liquid ammonia is [2008]

Solution:

Alkynes  having terminal –C ≡ H react with Na in liquid ammonia to yield H2 gas of the given compounds CH3CH2C ≡ CH can react with Na in liquid NH3 so the correct answer is (b).

QUESTION: 16

The treatment of CH3MgX with CH3C ≡ C-H produces   [2008]  

Solution:

Writing the reaction we get

So we find  that CH4 is produced in this reaction.

QUESTION: 17

One mole of a symmetrical alkene on ozonolysis gives two moles of an aldehyde having a molecular mass of 44 u. The alkene is[2010]

Solution:

The given molecular formula suggests that the aldehyde formed will be acetaldehyde hence the alkene  will be

QUESTION: 18

Ozonolysis of an organic compound gives formaldehyde as one of the products. This confirms the presence of : [2011]

Solution:

Compound must contain a vinyl group  in order to give formaldehyde as one of the product.

                                             

QUESTION: 19

Which branched chain isomer of the hydrocarbon with molecular mass 72u gives only one isomer of mono substituted alkyl halide ? [2012]

Solution:

QUESTION: 20

2-Hexyne gives trans-2-Hexene on treatment with :

Solution:

Anti addition of hydrogen atoms to the triple bond occurs when alkynes are reduced with sodium (or lithium) metal in ammonia, ethylamine, or alcohol at low temperatures. This reaction called, a dissolving metal reduction, produces an (E)- or trans-alkene.
Sodium in liq. NH3 is used as a source of electrons in the reduction of an alkyne to a trans alkene.

QUESTION: 21

Which compound would give 5 - keto - 2 - methylhexanal upon ozonolysis ?        [JEE M 2015]

Solution:

When 1, 3-dimethylcyclopentene is heated with ozone and then with zinc and acetic acid, oxidative cleavage leads to keto - aldehyde.

5- keto – 2 – methylhexanal

QUESTION: 22

The hottest region of Bunsen flame shown in the figure below is :         [JEE M 2016]

Solution:

Region 2 (blue flame) will be the hottest region of Bunsen flame shown in given figure

QUESTION: 23

At 300 K and 1 atm, 15 mL of a gaseous hydrocarbon requires 375 mL air containing 20% O2 by volume for complete combustion. After combustion the gases occupy 330 mL.Assuming that the water formed is in liquid form and the volumes were measured at the same temperature and pressure, the formula of the hydrocarbon is:  [JEE M 2016]

Solution:

Volume of O2 used =  = 75 ml

∴ From the reaction of combustion

1 ml CxHy requires =

So, 4x + y = 20
x = 3
y = 8

QUESTION: 24

The reaction of propene with HOCl (Cl2 + H2O) proceeds through the intermediate:        [JEE M 2016]

Solution: