Chemistry

Hydrocarbons

Question:

What is polymerization? Give an example.

Answer:

The process by which simple molecules join together to form large molecules is known as polymerization.
Simple alkenes polymerize to form long chain addition polymers.
For example, ethylene gives polyethylene.
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Hydrocarbons

Q 1.

In the alkane, CH3CH2—C(CH3)2—CH2—CH(CH3)2, identify 1 °, 2 °, 3 ° carbon atoms and give the number of H-atoms bonded to each one of these.

Q 2.

Convert ethylene to ethane.

Q 3.

What is the hybridisation of central carbon in 1,2-propadiene (CH2=C=CH2)?

Q 4.

Nucleophiles and electrophiles are reaction intermediates having electron rich and electron deficient centres respectively. Hence, they tend to attack electron deficient and electron rich centres respectively. Classify the following species as electrophiles and nucleophiles.
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Q 5.

Explain the term aromaticity. What are the necessary conditions for any compound to show aromaticity?

Q 6.

What happens when ethanol is heated with cone. H2SO4?

Q 7.

What are conformations?

Q 8.

Write the IUPAC names of the following compounds.
(i) (CH3)CCH2C(CH3)3    (ii) (CH3)2C(C2H5)2

Q 9.

The molecules having dipole moment are________ .
(a) 2,2-Dimethylpropane                                            
(b) trans-Pent-2-ene
(c) cw-Hex-3-ene            
(d) 2,2,3,3-Tetramethylbutane

Q 10.

Which is more acidic: ethene or ethyne and why?

Q 11.

Which of the following are correct?
(a) CH3 – O – CH+2 is more stable than CH3 – CH+2
(b) (CH3)2CH+ is less stable than CH3 – CH2 – CH+2
(c) CH2 = CH – CH+2 is more stable than CH3 – CH2 – CH+2
(d) CH2 = CH+ is more stable than CH3 – CH+2
 

Q 12.

The relative reactivity of 1 °, 2 ° and 3 ° hydrogens towards chlorination is 1: 3.8 : 5. Calculate the percentages of all monochlorinated products obtained from 2-methylbutane.
 

Q 13.

For the following compounds, write structural formulas and IUPAC names for all possible isomers having the number of double or triple bond as indicated:
(a) C4H8 (one double bond) (b) C5H8 (one triple bond)

Q 14.

How will you distinguish between propene and propane?

Q 15.

Arrange the following: HCl, HBr, HI, HF in order of decreasing reactivity towards alkenes.

Q 16.

What are Arenes ?

Q 17.

Why does the presence of a nitro group-make the benzene ring less reactive in comparison to the unsubstituted benzene ring? Explain.

Q 18.

Out of benzene, m-dinitrobenzene and toluene which will undergo nitration most easily and why?

Q 19.

What happens when benzene is treated with excess of Cl2 in presence of sunlight? Give chemical reaction.

Q 20.

Explain the following with examples:
(i) Wurtz reaction
(ii) Hydrogenation.

Q 21.

What is polymerization? Give an example.

Q 22.

How will you demonstrate that double bonds of benzene are somewhat different from that of olefins?

Q 23.

Why is benzene extra-ordinarily stable though it contains three double bonds?

Q 24.

What happens when benzene is treated with acetyl chloride in presence of AlCl3?

Q 25.

Define resonance energy. What is resonance energy of benzene?

Q 26.

Discuss the shape of methane and ethane.

Q 27.

Arrange the following carbanions in order of their decreasing stability.
(A) H3C-C ≡ C                                                                                
(B) H-C ≡ C
(C) H3C – CH2
(a) A>B>C
(b) B>A>C
(c) C>B>A
(d) C>A>B

Q 28.

What is Lindlar’s catalyst? Give its use.

Q 29.

Although benzene is highly unsaturated it does not undergo addition reactions. Why?

Q 30.

(a) Why are alkenes called unsaturated hydrocarbons?
(b) How will you test the presence of double bond in an alkene?
(c) Name the products formed when propene is subjected to ozonolysis.

Q 31.

Write structures of all the alkenes which on hydrogeneration give 2-methylbutane.

Q 32.

Suggest the name of another Lewis acid instead of anhydrous aluminium chloride which can be used during ethylation of benzene.

Q 33.

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Q 34.

What is decarboxylation ? Give an example.

Q 35.

An alkene ‘A’ contains three C-C, eight C-H σ bonds and one C-C Ï€ bond. ‘A' on ozonolysis gives two moles of an aldehyde of molar mass 44 u. Deduce IUPAC name of’A’.

Q 36.

What will be the product obtained as a result of the following reaction and why?

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Q 37.

What do you mean by pyrolysis?

Q 38.

What is Huckel rule?

Q 39.

How will you distinguish between acetylene and ethylene?

Q 40.

Discuss the preparation of alkanes by Wurtz reaction. What is the limitaHon of the reaction?

Q 41.

Which of the following alkenes on ozonolysis gives a mixture of ketones only?
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Q 42.

Rotation around carbon-carbon single bond of ethane is not completely free. Justify the statement.

Q 43.

How will you convert benzene into
(i) p-nitrobromobenzene (ii) m-nitrobromobenzene
 

Q 44.

An alkene ‘A’ contains three C—C, eight C—H, a-bonds, and one C—C n-bond. ‘A’ on ozonolysis gives two moles of an aldehyde of molar mass 44 u. Write the IUPAC name of’A’.

Q 45.

Explain why the following systems are not aromatic?
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Q 46.

Arrange the following set of compounds in order of their decreasing relative reactivity with an electrophile, E+.
(a) Chlorobenzene, 2, 4-dinitrochlorobenzene, p-nitrochlorobenzene
(b) Toluene,p—H3C—C6H4—NO2, p—O2N—C6H4—NO2.

Q 47.

Why are alkanes called paraffins?

Q 48.

Classify the following compounds into (i) alkanes (ii) alkenes (iii) alkynes (iv) arenes.  (a) C6H6 (b) C4H8 (C) C8H8 (d) C5H8 (e) C6H14

Q 49.

The intermediate carbocation formed in the reactions of HI, HBr and HC1 with propene is the same and the bond energy of HCl, HBr and HI is 430.5 kJ mol-1,363.7 kJ mol1 and 296.8 kJ mol-1 What will be the other of reactivity of these halogen acids?

Q 50.

Draw the cis- and trans-structures for hex-2-ene. Which iosmer will have higher b.p. and why?