Free Chemistry of Hydrocarbons MCQs with Answers
1,091 Chemistry of Hydrocarbons MCQs from Chemistry, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Hydrocarbons are studied through the structures and reactions of alkanes, alkenes, alkynes and aromatic compounds. Coverage includes free radical substitution in alkanes, electrophilic addition to carbon-carbon multiple bonds, benzene substitution, aromatic stability and the difference between addition reactions of alkenes and substitution reactions of benzene.
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Read the Chemistry of Hydrocarbons notesFree MDCAT chapter notes with key terms1,091 questions · page 5 of 55
- 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. CH3-CH2-CCH (1-Butyne)
- B. CH3-CCH(1-Propyne)
- C. CH3-CH2-CH2CCH(1-Pentyne)
- D. CH2=CH2
Explanation: Terminal alkynes such as 1-butyne, 1-propyne and 1-pentyne contain an acidic terminal hydrogen and form red copper acetylide precipitates…
Correct answer: CH2=CH2- A. Ethyne
- B. Ethene
- C. Ethane
- D. Benzene
Explanation: Ethyne has a terminal C-H bond attached to an sp-hybridised carbon. Its high s-character makes this hydrogen relatively acidic compared…
Correct answer: Ethyne- A. Glycol
- B. Glyoxal then formic acid
- C. Formaldehyde
- D. None
Explanation: Ozonolysis of acetylene first forms glyoxal, OHC-CHO, and further oxidation converts the aldehyde groups to formic acid.
Correct answer: Glyoxal then formic acid- A. CH3CH2CHO + CH3CHO
- B. CH3CH2CHO + CH3COOH
- C. CH3CH2COOH + CH3COOH
- D. CH3COOH + CO2
Explanation: In oxidative ozonolysis without zinc, 2-pentyne, CH3-C≡C-CH2CH3, is cleaved at the triple bond and both resulting fragments are oxidised…
Correct answer: CH3CH2COOH + CH3COOH- A. Acetone
- B. Acetaldehyde
- C. Acetic acid
- D. Ethyl alcohol
Explanation: Water adds across ethyne in the presence of HgSO4 and H2SO4 to form an unstable enol, CH2=CHOH.
Correct answer: Acetaldehyde- A. Methane
- B. Ethane
- C. Acetylene
- D. Ethene
Explanation: Acetylene burns with oxygen to produce an extremely hot flame, so the oxyacetylene flame is used for welding and cutting metals.
Correct answer: Acetylene- A. Bromine water
- B. Bayer's reagent
- C. Fehling solution
- D. Ammonical silver nitrate
Explanation: A triple bond in a terminal alkyne such as propyne, C3H4, is indicated by ammoniacal silver nitrate, which forms a precipitate of silver…
Correct answer: Ammonical silver nitrate92. Acetylene gives:
- A. White precipitate with AgNO3 and red precipitate with Cu2Cl2
- B. White precipitate with Cu2Cl2 and red precipitate with AgNO3
- C. White precipitate with both the reagents
- D. Red precipitate with both the reagents
Explanation: Terminal acetylene forms white silver acetylide with ammoniacal AgNO3 and red copper acetylide with ammoniacal cuprous chloride, written…
Correct answer: White precipitate with AgNO3 and red precipitate with Cu2Cl2- A. Alkane
- B. Alkene
- C. Alkyne
- D. All have same
Explanation: A terminal alkyne is more acidic because its conjugate base places the negative charge on an sp-hybridised carbon, which has greater…
Correct answer: Alkyne- A. CnH2n + 2
- B. CnH2n - 2
- C. CnH2n
- D. CnH2n + 2
Explanation: An open-chain alkyne has the general formula CnH2n-2 because it contains one triple bond, which represents two degrees of unsaturation.
Correct answer: CnH2n - 2- A. ethene
- B. ethyne
- C. ethyl halide
- D. all of the above are possible
Explanation: Complete dehalogenation of a tetrahaloethane removes four halogen atoms from the two-carbon framework, creating two pi bonds and forming…
Correct answer: ethyne- A. propyne
- B. 1-butyne
- C. ethyne
- D. all of the above
Explanation: Propyne, 1-butyne and ethyne are all terminal alkynes, so each has a hydrogen attached to a triple-bonded carbon and can show weak acidic…
Correct answer: all of the above- A. angular
- B. trigonal
- C. linear
- D. trigonal planar
Explanation: Ethyne, C2H2, contains a carbon-carbon triple bond. Each carbon is sp-hybridized, and sp orbitals are arranged 180° apart, so the molecule…
Correct answer: linear- A. Diviny1 acetylene
- B. Ethylidine dichloride
- C. Chloroprene
- D. 1 - 3 - 3 - trichloro butane
Explanation: Addition of one molecule of HCl to vinyl acetylene, CH2=CH-C≡CH, gives 2-chloro-1,3-butadiene, commonly called chloroprene.
Correct answer: Chloroprene- A. Addition reaction
- B. Substitution reactions
- C. Halogenation
- D. All of these
Explanation: Benzene mainly undergoes electrophilic substitution because substitution preserves its especially stable aromatic ring, whereas addition…
Correct answer: Substitution reactions- A. Unsaturations
- B. Cyclic structure
- C. Presence of 4nπ electrons
- D. Presence of 4n+2π electrons
Explanation: Aromatic compounds require a cyclic, planar, continuously conjugated system containing 4n + 2 pi electrons, according to Huckel's rule.
Correct answer: Presence of 4n+2π electrons