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.
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- A. ethane
- B. ethene
- C. ethyne
- D. methane
Explanation: Ethene is used for artificial fruit ripening because it acts as a plant hormone that initiates and accelerates ripening changes.
Correct answer: ethene- A. less reactivity
- B. addition reactions
- C. substitution reactions
- D. none
Explanation: The pi bond in an unsaturated hydrocarbon is relatively exposed and can break while new sigma bonds form, so unsaturated hydrocarbons…
Correct answer: addition reactions- A. dihalo alkane
- B. trihalo alkane
- C. vicinal dihalo alkane
- D. vicinal trihalo alkane
Explanation: Dehalogenation of a vicinal dihaloalkane removes halogen atoms from adjacent carbon atoms, allowing a carbon-carbon double bond to form…
Correct answer: vicinal dihalo alkane- A. ethane
- B. ethyne
- C. ethene
- D. benzene
Explanation: Ethene is the most reactive among these choices under ordinary addition-reaction conditions because its carbon-carbon pi bond readily…
Correct answer: ethene- A. reduction
- B. oxidation
- C. hydrolysis
- D. rearrangement
Explanation: Ozone first adds to an alkene to form an unstable molozonide, which rearranges by bond reorganisation into the more stable ozonide.
Correct answer: rearrangement- A. CnH2n
- B. CnH2n+2
- C. CnH2n-1
- D. CnH2n-2
Explanation: A cycloalkene has one ring and one double bond, giving two degrees of unsaturation.
Correct answer: CnH2n-2- A. Substitution reaction
- B. Elimination reaction
- C. Addition reaction
- D. Condensation reaction
Explanation: Catalytic hydrogenation of alkenes exhibits addition reactions. Addition reactions in an unsaturated compound mean a compound that has a…
Correct answer: Addition reaction- A. 2 Butene
- B. 3,4-Dimethyl-3-hexene.
- C. 3-methyl-3-hexene
- D. 2 - Hexene.
Explanation: The ozonolysis of 3,4-dimethyl-3-hexene involves breaking the carbon-carbon double bond, resulting in the formation of carbonyl compounds.
Correct answer: 3,4-Dimethyl-3-hexene.- A. 2-Butene
- B. 2-Methyl-2-Butene
- C. 2-Pentene
- D. 2-Methyl-2-Pentene
Explanation: The ozonolysis of 2-methyl-2-butene (also known as tert-butyl ethylene) proceeds as follows: The double bond in 2-methyl-2-butene reacts…
Correct answer: 2-Methyl-2-Butene- A. Acetaldehyde
- B. Acetone
- C. Formaldehyde
- D. Benzaldehyde
Explanation: Acetone is formed in the ozonolysis of 3-dimethyl-2-butene. The double bond in the alkene is cleaved, and the resulting carbonyl groups…
Correct answer: Acetone- A. C3H6 + Br2
- B. C2H4 + HCl
- C. C3H8 + Br2
- D. C3H6 + HBr
Explanation: Markovnikov's rule states that for a hydrogen halide being added to an asymmetric alkene, the hydrogen attaches itself to the carbon…
Correct answer: C3H6 + HBr- A. 1.20Å
- B. 1.34Å
- C. 1.54Å
- D. 1.68Å
Explanation: The bond length of the Carbon-Carbon double bond, as observed in ethene is 1.34Å.
Correct answer: 1.34Å- A. Alkanes
- B. Alkenes
- C. Alkynes
- D. Benzene
Explanation: Alkenes are the most reactive of all options in terms of electrophilic addition reactions because the presence of the double bond allows…
Correct answer: Alkenes- A. dil.alkaline KMnO4 soln.
- B. HCl+ZnCl2
- C. New in CCl4
- D. All of these
Explanation: Baeyer's reagent is a dilute alkaline potassium permanganate solution, which is commonly used to test for the presence of unsaturation in…
Correct answer: dil.alkaline KMnO4 soln.- A. 1 - pentene
- B. 2 - methyl propene
- C. 2 - butene
- D. 2,3 - dimethyl - 2 - butene
Explanation: You're looking for an alkene that, when cleaved by ozonolysis, produces only one type of aldehyde.
Correct answer: 2 - butene- A. Formic acid + acetic acid
- B. Two moles of methanoic acid
- C. Two moles of ethanoic acid
- D. Ethylene glycol
Explanation: 2-butene is a symmetrical alkene, and when it undergoes oxidative cleavage with hot alkaline KMnO4, each carbon-carbon double bond is…
Correct answer: Two moles of ethanoic acid37. The amount (in litres) of Oxygen at STP that is required for the combustion of 4gm of ethylene is:
- A. 96 litres
- B. 9.6 litres
- C. 44.8 litres
- D. 67.2 litres
Explanation: 4gm of Ethylene (C2H4) = 0.1428 moles or 3.2L of it. The Balanced Chemical Equation for this reaction is: C2H4+ 3O2 -> 2CO2 + 2H2O+ energy…
Correct answer: 9.6 litres- A. Alkanes
- B. Alkenes
- C. Alkynes
- D. Benzene
Explanation: Alkanes are least reactive, followed by benzene. Alkenes are more reactive than alkynes.
Correct answer: Alkenes- A. sp2
- B. sp3
- C. sp2d
- D. sp
Explanation: Remember that alkanes have sp3 hybridization, alkenes have sp2 hybridization and alkynes have sp hybridization.
Correct answer: sp2- A. Ethane
- B. Ethyne
- C. Ethylbenzene
- D. Ethene
Explanation: Alkanes cannot be oxidized; rather they can be oxidized only when burned in the presence of O2 to give carbon dioxide and water.
Correct answer: Ethane