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. Free radical substitution
- B. Electrophilic addition
- C. Nucleophilic substitution
- D. Electrophilic substitution
Explanation: The exposed pi electrons of the double bond attract electrophiles, which add across the bond and convert an unsaturated compound into a…
Correct answer: Electrophilic addition- A. sodium metal
- B. silver nitrate solution
- C. bromine water, which is decolourised by the alkene
- D. limewater
Explanation: The orange colour of bromine water disappears as bromine adds across the double bond to form a colourless dibromo compound, and an alkane…
Correct answer: bromine water, which is decolourised by the alkene- A. 1-bromopropane
- B. 2-bromopropane
- C. 1,2-dibromopropane
- D. propan-2-ol
Explanation: The hydrogen adds to the carbon that already carries more hydrogens, so the bromine ends up on the middle carbon.
Correct answer: 2-bromopropane- A. sp3 and 109.5 degrees
- B. sp and 180 degrees
- C. sp2 and 120 degrees
- D. sp2 and 109.5 degrees
Explanation: Each carbon forms three sigma bonds using sp2 hybrids arranged in a plane at 120 degrees, and the remaining unhybridised p orbitals…
Correct answer: sp2 and 120 degrees- A. ethane
- B. ethanoic acid
- C. ethanol
- D. ethanal
Explanation: Ethene adds sulphuric acid to give ethyl hydrogen sulphate, and hydrolysing that with water releases ethanol and regenerates the acid…
Correct answer: ethanol- A. dehydration
- B. hydrogenation
- C. hydrolysis
- D. halogenation
Explanation: Hydrogen adds across the double bond to give the corresponding alkane, and this is the process used to convert liquid vegetable oils into…
Correct answer: hydrogenation- A. Ethylene only
- B. Acetaldehyde and Formaldehyde
- C. Propionaldehyde and Formaldehyde
- D. Acetaldehyde only
- E. Acetaldehyde and Oxalic acid
Explanation: Reductive ozonolysis cleaves the double bond of 1-butene, CH2=CH-CH2-CH3, into methanal, HCHO, from the terminal carbon and propanal…
Correct answer: Propionaldehyde and Formaldehyde- A. Ethylene oxide
- B. HCHO
- C. Ethylene glycol
- D. Ethyl alcohol
Explanation: Ethene reacts with ozone to form an ozonide, and hydrolysis of this ozonide cleaves the C=C bond.
Correct answer: HCHO- A. Ozonolysis
- B. Oxidation
- C. Reduction
- D. Hydrogenation
Explanation: Ozonolysis breaks a carbon-carbon double bond and produces carbonyl compounds whose structures reveal which groups were attached to the…
Correct answer: Ozonolysis- A. CnH2n+1
- B. CnH2n+2
- C. CnH2n
- D. CnH2n-2
Explanation: An open-chain alkene with one carbon-carbon double bond has the general formula CnH2n, because the double bond removes two hydrogen atoms…
Correct answer: CnH2n- A. Alkenes Family
- B. Saturated hydrocarbon
- C. Aromatic hydrocarbon
- D. None of These
Explanation: Ethene, C2H4, contains a carbon-carbon double bond and is the simplest member of the alkene homologous series.
Correct answer: Alkenes Family- A. Ethylene oxide
- B. HCHO
- C. Ethylene glycol
- D. Ethyl alcohol
Explanation: Ozonolysis cleaves the C=C bond in ethene, CH2=CH2, and each carbon becomes a methanal molecule, HCHO, after hydrolysis of the ozonide.
Correct answer: HCHO- A. Permanent effect
- B. Operate due to electronegativity difference
- C. temporary effect
- D. None of the above
Explanation: The electromeric effect is a complete temporary transfer of the pi-electron pair of a multiple bond towards one atom when an attacking…
Correct answer: temporary effect- A. Reasonable
- B. no bond reasonable
- C. Inductive effect
- D. Electromeric effect
Explanation: Hyperconjugation is delocalization of electrons from a sigma C-H or C-C bond into an adjacent empty or pi-antibonding orbital.
Correct answer: no bond reasonable- A. Aromatic
- B. Alicyclic
- C. Aliphatic
- D. None of These
Explanation: Cyclopentene is a non-aromatic cyclic hydrocarbon, so it is classified as alicyclic.
Correct answer: Alicyclic- A. polyacetylene
- B. benzene
- C. chloroprene
- D. divinyl acetylene
Explanation: Hydrogen chloride adds across the triple bond of vinylacetylene to produce chloroprene, CH2=CCl-CH=CH2, a conjugated diene used in making…
Correct answer: chloroprene- A. Ni-Cu alloy
- B. Ni-Fe alloy
- C. Ni-Al alloy
- D. Ni-Mg alloy
Explanation: Raney nickel is prepared from a nickel-aluminium alloy by treating it with concentrated sodium hydroxide, which dissolves aluminium and…
Correct answer: Ni-Al alloy- A. alkane
- B. alkene
- C. alkyne
- D. both B & C
Explanation: Both alkenes and alkynes contain pi bonds, and their exposed pi electrons make them more reactive than saturated alkanes in addition…
Correct answer: both B & C- A. Aalkene & H2
- B. alkene & O2
- C. alkene & N2
- D. alkyne & Cl2
Explanation: The Sabatier-Senderens reaction hydrogenates an alkene by adding H2 across its carbon-carbon double bond in the presence of nickel…
Correct answer: Aalkene & H2- A. halogenation
- B. hydroxylation
- C. hydrogenation
- D. hydration
Explanation: Vegetable oils contain unsaturated carbon-carbon bonds, and hydrogenation adds H2 across these bonds in the presence of a catalyst such as…
Correct answer: hydrogenationAlkenes MCQs: common questions
Are these Alkenes MCQs free?
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There are 89 Alkenes MCQs in the Chemistry bank, shown 20 to a page with the correct answer and an explanation on each.
Does every Alkenes MCQ have an explanation?
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