TestUstad

Free Alkenes MCQs with Answers

89 Alkenes MCQs from Chemistry, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.

Alkenes are unsaturated hydrocarbons containing a carbon-carbon double bond with sigma and pi components and restricted rotation. Their reactions include electrophilic addition of hydrogen, halogens, hydrogen halides and water, with Markovnikov orientation, oxidation, combustion and polymerisation, while their preparation commonly involves elimination from alkyl halides or alcohols.

Last updated

89 questions · page 5 of 5

81. In the CH3CH2C = CH + H2O ->?

  • A. CH3CHO + CH3CHO
  • B. CH3CH2CH2CH2 - OH
  • C. CH3CH2CH2COOH
  • D. CH3CH2COCH3

Explanation: The correct answer is D:CH3CH2COCH3. When water is added to an alkyne, it typically undergoes a hydration reaction resulting in the…

Read the full explanation →
Correct answer: CH3CH2COCH3

82. Alkene+O3→Ozonide "Zn+H2O"→Propanone+Propanal, The IUPAC name of alkene is:

  • A. Hex-2-ene
  • B. Hex-3-ene
  • C. 2-methyl pent-1-ene
  • D. 2-methyl pent-2-ene

Explanation: d) 2-methyl pent-2-ene:2-methyl pent-2-ene is a five-carbon alkene with a methyl group attached to the second carbon atom and the double…

Read the full explanation →
Correct answer: 2-methyl pent-2-ene

83. Propene reacts with hypochlorous acid to form

  • A. CH3-CH-CH2O ⋮ ClOHCl
  • B. CH3-CH-CH2Cl ⋮ OH
  • C. CH3-CH2-CH2Cl ⋮ OH
  • D. CH3-CH-CH2 ⋮ OH

Explanation: The reaction between propene and hypochlorous acid (HOCl) can be represented as follows:CH3CH=CH2 + HOCl → CH3CH(OH)CH2ClThe product…

Read the full explanation →
Correct answer: CH3-CH-CH2Cl ⋮ OH

84. A gas decolorized alkaline KMnO4 solution but does not give any PPT with ammoniacal AgNO3

  • A. Methane
  • B. Ethylene
  • C. Ethane
  • D. None of the above

Explanation: Option d) "None of the above" is incorrect because ethylene (option b) decolorizes KMnO4 but does not give a precipitate with ammoniacal…

Read the full explanation →
Correct answer: Ethylene

85. An olefin "X" on ozonolysis gives CH3CH2COCH3 and CH3COCH3. The IUPAC name of X is:

  • A. 2 - Butene
  • B. 2,3 di Methyl-2 Pentene
  • C. 2 - Pentene
  • D. 1 - Hexene

Explanation: The longest carbon chain is of 5 carbons so the name ends with pentene and since there are two methyl groups as branches so option B is…

Read the full explanation →
Correct answer: 2,3 di Methyl-2 Pentene

86. The order of decreasing reactivities of alkanes, alkenes and alkynes is:

  • A. Alkanes > Alkenes > Alkynes
  • B. Alkynes > Alkenes > Alkanes
  • C. Alkenes > Alkynes > Alkanes
  • D. Alkenes = Alkynes > Alkanes

Explanation: The order of decreasing reactivities for alkanes, alkenes, and alkynes is as follows: alkynes > alkenes > alkanes.

Read the full explanation →
Correct answer: Alkenes > Alkynes > Alkanes

87. The addition of hypo-chicrous acid to 1 butene gives:

  • A. 1-chloro 1-butanol
  • B. 2-chloro 1-butanol
  • C. Both (A) and (B)
  • D. None of the above

Explanation: When hypochlorous acid (HClO) reacts with 1-butene, the main product formed is 1-chloro-1-butane.

Read the full explanation →
Correct answer: None of the above

88. 3-Ethyl-2-Pentene on ozonolysts gives:

  • A. 2-Pentanone
  • B. pentanol
  • C. 3-Pentanone and Ethanal
  • D. 7-Heptanone

Explanation: When 3-Ethyl-2-Pentene undergoes ozonolysis, it reacts with ozone (O3) to form two pentanone molecules.

Read the full explanation →
Correct answer: 2-Pentanone

89. Which is the most stable hydrocartion?

  • A. cis-2-butene
  • B. Isobutylene
  • C. trans-2-butene
  • D. 1-butene

Explanation: trans-2-butene is the most stable option among the given choices because it has a straight-chain configuration with no steric…

Read the full explanation →
Correct answer: trans-2-butene
Start Free Alkenes Practice MCQs Test