Chemistry

Hydrocarbons

Question:

How will you distinguish between acetylene and ethylene?

Answer:

Acetylene forms precipitate with ammoniacal silver nitrate solution, ethylene does not react with these reagents.

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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.

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

Q 3.

Convert ethylene to ethane.

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.
ncert-exemplar-problems-class-11-chemistry-chapter-13-hydrocarbons-46

Q 5.

What happens when ethanol is heated with cone. H2SO4?

Q 6.

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

Q 7.

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 8.

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

Q 9.

What are conformations?

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 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 13.

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 14.

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 15.

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

Q 16.

How will you distinguish between propene and propane?

Q 17.

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

Q 18.

What are Arenes ?

Q 19.

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

Q 20.

What is polymerization? Give an example.

Q 21.

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

Q 22.

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

Q 23.

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

Q 24.

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

Q 25.

Discuss the shape of methane and ethane.

Q 26.

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

Q 27.

What is decarboxylation ? Give an example.

Q 28.

Define resonance energy. What is resonance energy of benzene?

Q 29.

Write down the products ofozonolysis ofl, 2-dimethylbenzene (o-xylene). How does the result support Kekule structure of benzene?

Q 30.

How will you distinguish between acetylene and ethylene?

Q 31.

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

Q 32.

Why does benzene undergo electrophilic substitution reactions easily and nucleophilic substitutions with difficulty?

Q 33.

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

Q 34.

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

Q 35.

What do you mean by pyrolysis?

Q 36.

What is Lindlar’s catalyst? Give its use.

Q 37.

(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 38.

ncert-solutions-class-11th-chemistry-chapter-13-hydrocarbons-34

Q 39.

Which are the correct IUPAC names of the following compound
ncert-exemplar-problems-class-11-chemistry-chapter-13-hydrocarbons-20

(a) 5-(2′,2′-Dimethylpropyl)decane
(b) 4-Butyl-2,2-dimethylnonane
(c) 2,2-Dimethyl-4-pentyloctane
(d) 5-neo-Pentyldecane

Q 40.

What is electrophile in sulphonation?

Q 41.

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 42.

Why are alkanes called paraffins?

Q 43.

What is Huckel rule?

Q 44.

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

Q 45.

(a) What effect the branching of an alkane has on its melting point?
(b) Which of the following has highest boiling point?
(i) 2-methyl pentane
(ii) 2, 3-diethyl butane
(iii) 2, 2-dimethyl butane

Q 46.

How will you separate propene from propyne?

Q 47.

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

Q 48.

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 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?