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ALKYNE

1. Which of the following gases is used for welding
A. Acetylene
Explanation : 
                               
The combustion of acetylene is highly exothermic and the heat produced during the combustion can be used for welding purposes in the form of oxy acetylene flame.

 

2. A metallic carbide on treatment with water gives a colourless gas which burns readily in air and which gives a precipitate with ammoniacal silver nitrate solution. Gas evolved is
A.  Acetylene
Explanation :


                           

 

3. 1-butyne reacts with cold alkaline KMnO4 to produce
A. CH3CH2COOH + CO2

Explanation :


                            

 

4. Identify the product D in the following series of reaction

A. Acetylene
Explanation:


                          

 

5. The correct order towards bond length is
A. C ≡ C < C = C < C - C
Explanation:


                               

 

6. In the molecule CH ≡ C - CH = CH2 , the hybridisation of C - C bond is
A. sp2 - sp
Explanation:


                              

 

7. The product formed when acetylene is passed through red hot tube is
A. Benzene
Explanation:


                               

 

8. Acetylenic hydrogens are acidic because
A. Sigma electron density of C–H bond in acetylene is nearer to carbon, which has 50% s-character

 

9. Which is the most suitable reagent among the following to distinguish compound (iii) from rest of the compounds?

(i) CH3 - C  ≡ C - CH3
(ii) CH3 - CH2 - CH2 - CH3
(iii) CH3 - CH2 - C  ≡ CH
(iv) CH3 - CH = CH2
A. Ammoniacal silver nitrate reagent

10. A hydrocarbon of formula C6 H10 absorbs only one molecule of H2 upon catalytic hydrogenation. Upon ozonolysis, the hydrocarbon yields

The hydrocarbon is
A. Cyclohexene
Explanation:


                          

 

11. Poisonous gas ‘Lewissite’ is obtained by the reaction of
A. CH  ≡ CH and AsCl3
Explanation: 


                             

 

12. Products of the following reaction      ....... are
A. CH3COOH + HOOCCH2CH3
Explanation:


                               

 

13. By coaltar distillation, which is not obtained
A. Mobil oil

 

14. Hydrocarbon containing following bond is most reactive
A. C ≡ C
Explanation: -C  ≡ C - is most reactive because sp-hybridization.

 

15. The shapes of methane, ethene and ethyne molecules are, respectively
A. Tetrahedral, planar and linear

 

16. To synthesize the unsymmetrical alkyne CH3 - C ≡ C - CH2 - CH3 the reagents needed would be
A. Ethyne, iodomethane, iodoethane and sodamide
Explanation:

 

17. When propyne is treated with dilute H2SO4 and HgSO4, the major product is

A. Propanone
Explanation:

 

18. Which of the following will be the final product when C2H2 reacts with HCl

A. 
         
Explanation:


 

19. What is the end product of the following sequences of operations

A. C2H5OH
Explanation:

 


        The reagent is
A. KOH in C2H5OH
Explanation:

This reaction is an example of dehydrohalogenation Hence, alcoholic KOH is used as a reagent.
 

21. Acetylene can be prepared from
(a) Potassium fumarate      (b) Calcium carbide      (c) Ethylene bromide      (d) All of these
A. All of these

Explanation: 

 

22. Acetylene is obtained by the electrolysis of
A. Potassium fumarate
Explanation:


23. The compound C3H4 has a triple bond, which is indicated by its reaction with
A. Ammonical silver nitrate
Explanation:


A. Ethyl bromide
Explanation:

A. Cycloctatetraene
Explanation:

 

26. A salt producing hydrocarbon among these compounds is
A. Ethyne
Explanation: Ethyne have acidic hydrogen to form salt.

 

27. An unknown compound A has a molecular formula C4H6 . When A is treated with an excess of Br2 a new substance B with formula C4H6Br4 is formed. A forms a white precipitate with ammoniacal silver nitrate solution. A may be
A. Butyne-1
Explanation:


Since the molecule takes 2 moles of Br2 . Therefore it is alkyne. Also it gives white ppt with Tollen’s reagent therefore acidic H is present. Hence it is 1-Butyne.
 

28. Which of the following reacts with sodium with the elimination of hydrogen
        (a) CH4        (b) C2H6         (c) C2H4         (d) C2H2
A. C2H2
Explanation: 2CH  ≡ CH + 2Na   2CH ≡  C- Na+ + H2

 

29. Acetylene gives
A. White precipitate with AgNO3 and red precipitate with Cu2Cl2
Explanation:

 

30. The bond length between sp3 hybridised carbon atom and other carbon atom is minimum in
A. Propyne

 

31. The C - H bond length is minimum in the bond formed by
A. sp - s overlapping (as in alkynes)

 

32. Which of the C - C bond is strongest
A. Formed by sp - sp hybridised carbon atoms (as in alkynes)
Explanation: sp - sp > sp2 - sp> sp3 - sp3
Order of bond strength

 

33. Which of the following pairs has the same bond angle
A. Ethylene and benzene
Explanation: Ethylene and Benzene
   120°                 120°
    sp2                   sp2

 

34. The product(s) obtained via oxymercuration (HgSO4 + H2SO4 ) of 1-butyne would be
A. 
Explanation: 


 

35. A compound is treated with NaNH2 to give sodium salt. Identify the compound

A. C2H2
Explanation:

 

36. A gas decolourises bromine in CCl4 and forms a precipitate with ammoniacal silver nitrate. The gas is
A. C2H2
Explanation :

 

37. Among the following compounds which have more than one type of hybridisation for carbon atom
(i) CH3CH2CH2CH3
(ii) CH3 - CH = CH - CH3
(iii) CH2 = CH - C  CH

(iv) H - C   C - H
A. (iii) and (iv)

 

38. The homologue of ethyne is
A. C3H4
Explanation : C2H2 and C3H4 are homologue because they differ by -CH2 group. Both have triple bond in their molecule.

 

39. When acetylene reacts with HCl in the presence of HgCl2 , the product is
A. Vinyl chloride
Explanation :


                    

 

40. When propyne reacts with aqueous H2SO4 in the presence of HgSO4, the major product is
A. Acetone
Explanation :


                          

41. Propyne on polymerisation gives
A. Mesitylene
Explantion :

 

42. When treated with ammoniacal cuprous chloride, which one among the following forms copper derivative?
A. C2H2
Explanation :

 

43. Which of the following catalyst is used in the polymerisation of CH  CH to C6H6
A. AlCl3
Explanation :

 

44. KMnO4 will oxidise acetylene to
A. Oxalic acid
Explanation :

 

45. Ethyne on reaction with dil. H2SO4 and Hg(II) gives
A. Ethanal
Explanation :

 

46. Which of the following is used to distinguish ethylene and acetylene?
A. Ammoniacal cuprous chloride
Explanation : Acetylene reacts with ammonical cuprous chloride to give brown ppt where as ethylene does not give this reaction.

 

47. The distinguishing test for triple bond containing acidic hydrogen is
A. (a) Ag(NH3)+2
Explanation : Ag(NH3)+2 gives white ppt with terminal alkynes.

 

48. If acetylene is passed through an electric arc in the atmosphere of nitrogen, the compound formed is
A. HCN

 

49. Ozonolysis of acetylene gives
A. Glyoxal, formic acid

 

50. The bond length between the hybridised carbon atom and other carbon atom is minimum in
A. Propyne
Explanation : Bond length decreases with increase in number of bonds.

 

51. The reaction of propene with HOCl proceeds via the addition of
A. Cl+ and OH- in a single step

 

52. Acetylene reacts with ammonical AgNO3 forming
A. Silver acetylene

 

53. Ethylidine dichloride can be prepared by the reaction of HCl and
A. C2H2

 

54. Which of the following order of reagent is chosen to prepare 1, 3-butadiene from C2H2
A. CuCl / NH4Cl and H2 / Pd(BaSO4)

 

55. Benzene is the polymer of
A. Ethyne
Explanation :

 

56.   reacts with acetic acid in presence of Hg2+ to give

A. 
Explanation : Reaction of acetic acid with acetylene is catalysed by Hg2+ salts.

 

57. Acetylene is prepared industrially by passing electric discharge through graphite electrodes in the atmosphere of
A. H2
Explanation : 

 

58. When acetylene is passed into dilute sulphuric acid containing Hg2+ ions, the product formed is
A. Acetaldehyde

Explanation :

59. Which of the following has acidic hydrogen?
        (a) Ethyne      (b) Ethene       (c) Ethane        (d) Benzene
A. Ethyne
Explanation : 2CH  CH + 2Na  2CH  C-Na+ + H2
Reaction with sodium metal shows that hydrogen is acidic.

 

60. Xylenes on oxidation with acidic KMnO4 gives
(a) Terphthalic acid        (b) Phthalic acid         (c) Isophthalic acid         (d) All of these
A. All of these

 

61. The structure of the product(Z) in the reactions given below 

  is

A. 


         

 

62. Carbon-carbon bond length is minimum in
A. Ethyne

 

63. Triple bond of ethyne is made of or Cylindrical shape of an alkyne is due to
A. Two π and one σ - bond
Explanation : In CH  CH triple bond consists of one σ and two π bonds.

 

64. An organic compound has a triple bond and not double bond. It can be tested by
A. Ammonical silver nitrate

 

65. Which of these will not react with acetylene
A. NaOH
Explanation : Nucleophiles and alkalies normally do not react with acetylene. Thus NaOH does not react.

 

66. What is the product when acetylene reacts with hypochlorous acid?
A. Cl2CHCHO
Explanation :

 

67. The alkene C6H10 producing OHC -(CH2)4 - CHO on ozonolysis is
A. Cyclohexene

 

68. The number of moles of proton which can be easily given by butyne-1(1 mole) is
A. 1

 

69. Which will undergo reaction with ammoniacal AgNO3
A.  
Explanation : CH3 - CH = CH - C  C - H . Acidic hydrogen
(H atom attached to triple bond) is present therefore it gives reaction with ammoniacal AgNO3.

 

70. Acetylene gas when passed through the 20% H2SO4 at 80oC gives acetaldehyde. The catalyst required for this conversion is
A. HgSO4
Explanation :

 

71. Which of the following reactions will yield 2, 2-dibromopropane
A. CH3C  CH + 2HBr 
Explanation :

 

72. Which of the following does not give white precipitate with ammoniacal AgNO3
A. CH3 - C  C - CH3

Explanation : CH3 - C  C - CH3, 2-butyne does not have acidic hydrogen. Hence, does not give white ppt. with ammonical AgNO3 solution.

 

A. 
Explanation :


                 

 

74. Which is represented by the formula CnH2n -2
A. Alkyne

 

 

75. What is the major product of the following reaction

A.


         

 

76. A compound C5H8 which give white ppt. with ammonical AgNO3. A give (CH3)2 CHCOOH with hot alcoholic KOH then compound is
A. (CH3)2CH - C  CH

 

77. 1, 2-dibromoethane when heated with alcoholic potash gives
A. Acetylene
Explanation :

 

78. Which of the following is not a member of homologous series
A. 2-butyne
Explanation : All are alkenes but 2-butyne is not.

 

79. The compound formed as a result of potassium permanganate oxidation of ethylbenzene is
A. Benzoic acid

 

80. What is the product when 2-butyne is treated with liquid NH3 in presence of lithium
A. trans-2-butene
Explanation : Reduction of alkynes with liquid NH3 / Li gives trans alkenes.

 

81. Distinction in pentene-1 and pentyne-1 is done by
A. [Ag(NH3)2]+

 

82. A mixture of ethane, ethene and ethyne is passed through ammoniacal AgNO3 solution. The gases which remain unreacted are
A. Ethane and ethene
Explanation : Ethyne reacts with ammonical AgNO3 to give white ppt of silver acetylide while ethane and ethene do not react because acidic hydrogen is absent.

 

83. In its reaction with silver nitrate acetylene shows

A. Acidic property
Explanation : Acidic property because H atoms are replaced by Silver metal atoms.

 

84. Simplest alkyne is represented by
A. C2H2

 

85. Which of the following bonds is most acidic
      (a) = C – H  (b) –C – H   (c)  C – H   (d) All are equally acidic
A.  C - H

 

86. The hybridisation in methane, ethene and Ethyne respectively is
A. sp3, sp2 and sp

 

87. Number of acidic hydrogen atoms in butyne-1 are
A. 1
Explanation : The hydrogen atom which is attached to triple bond is acidic.

 

88. Which of the following shows linear structure
        (a) Ethane       (b) Ethene         (c) Acetylene       (d) CCl4
A. Acetylene
Explanation : In acetylene both carbons are sp-hybridised so it has linear structure.

 

89. Calcium carbide on reacting with water gives
A. Acetylene

Explanation :

 

90. Addition of HCN to ethyne in presence of Ba(CN)2 as catalyst gives
A. Vinyl cyanide
Explanation :

 

91. Which compound will react with an aqueous solution of Ag(NH3)2+OH-
A. CH3CH2C  CH
Explanation : Because CH3CH2 - C  CH has one acidic hydrogen.

 

92. Which of the following give H2 gas with Na
A. C2H2
Explanation : 

 

(a) CH3COOH           (b) HCOOH           (c) Both (a) and (b)           (d) CH3CHO + HCHO
A. Both (a) and (b)

 

94. The number of π - bonds in the product formed by passing acetylene through dilute sulphuric acid containing mercuric sulphate is
A. One
Explanation :

 

95. Which of the following is weakly acidic
A. CH3 - C  C - CH3
Explanation : CH3 - C  C - CH3 has not acidic character.

 

96. Which of the following reactions is shown by alkynes
(a) Addition (b) Substitution (c) Polymerization (d) All of these
A. All of these
Explanation :

 

97. Shortest C–C bond length is present in
A. CH  C - C  CH
Explanation : Bond length decrease with increase in Bond order. Hence triple bonded carbon has minimum bond length.
C – C bond length = 1.54 Å
C = C bond length = 1.33 Å
 C bond length = 1.22 Å

 

98. Acetylene can be obtained by the reaction
A. 
Explanation : Acetylene can be obtained by the reaction of silver and chloroform (or iodo form)

 

99. Which of the following used for the conversion of 2-hexyne into trans-2-hexane
A. Li - NH3 /C2H5OH
Explanation : The partial reduction of alkynes by active metal in liquid ammonia takes place through trans vinylic anion which ultimately produces trans alkene.

 

100. In which of the following, the bond length between hybridized carbon atom and other carbon atom is minimum
A. Propyne
Explanation : We know that C – C bond length = 1.54 A, C = C bond length =1.34A and C  C bond length = 1.20A. Since propyne has triple bond; therefore it has minimum bond length.

 

101. What happens when a mixture of acetylene an hydrogen is passed over heated Lindlar’s catalyst
A. Ethylene is formed
Explanation :


                            

 

102. In acetylene molecule, the two carbon atoms are linked by
A. One sigma bond and two pi bonds
Explanation : 


 

103. Which reacts with ammoniacal AgNO3

A. Propyne
Explanation : Propyne reacts with ammoniacal AgNO3 due to presence of acidic hydrogen atom.
CH3C  CH + AgNO3 + NH4OH  CH3C  CAg + NH4 NO3 + H2O

 


 
A. CH3CH(Br)CH3
Explanation :

 

105. Carbide, which react with water to give propyne is
A. Mg2C3
Explanation : Mg2C3 + 4H2O  CH3C  CH + 2Mg(OH)2

Posted Date : 19-02-2021

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