Free Alkanes MCQs with Answers
127 Alkanes MCQs from Chemistry, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Alkanes are saturated hydrocarbons containing only carbon-carbon and carbon-hydrogen single bonds, with the general formula CnH2n+2 for open chains. Their structure, isomerism, IUPAC nomenclature, physical properties, combustion, free-radical halogenation and conformations are covered, including the difference between substitution in alkanes and addition in unsaturated hydrocarbons.
Last updated
127 questions · page 3 of 7
- A. Isomerization
- B. Adding (C2H5)4 Pb
- C. Adding (CH3)4 Pb
- D. All
Explanation: Octane number can be increased by converting straight-chain hydrocarbons into branched isomers and by using antiknock additives such as…
Correct answer: All- A. PbCl2
- B. (C2H5)4 Pb
- C. (C2H5)2 Pb
- D. all of the above
Explanation: Tetraethyl lead, (C2H5)4Pb, was historically added to petrol to increase octane rating and reduce engine knocking.
Correct answer: (C2H5)4 Pb43. The metallic sound produced by engine due to the pre-ignition of fuel is called _______________?
- A. knocking
- B. reforming
- C. cracking
- D. a and c
Explanation: Knocking is the metallic sound caused by abnormal, premature or uncontrolled ignition of the fuel-air mixture in an engine.
Correct answer: knocking- A. polymerization
- B. pyrolysis
- C. isomerism
- D. no such process occurs
Explanation: Pyrolysis is the thermal decomposition of a large molecule into smaller molecules in the absence of oxygen; hydrocarbon cracking is a…
Correct answer: pyrolysis- A. n. butane
- B. Ethanol
- C. Ethane
- D. Diethy1 ether
Explanation: Reduction replaces the chlorine atom in ethyl chloride, CH3CH2Cl, with hydrogen: CH3CH2Cl + 2[H] -> CH3CH3 + HCl.
Correct answer: Ethane- A. Alkenes
- B. Alkynes
- C. Alkanes
- D. Benzene
Explanation: Both alkenes and cycloalkanes have general formula CnH2n.
Correct answer: Alkenes- A. Butane
- B. Propane
- C. Pentane
- D. Hexane
Explanation: In the Wurtz reaction, two alkyl halides react with sodium to form a higher alkane.
Correct answer: Propane- A. Cannizaro's reaction
- B. Kolbe's reaction
- C. Sabatier & Senderen's reaction
- D. Wurtz reaction
Explanation: Option D is correct as the Wurtz reaction is an organic chemical coupling reaction wherein sodium metal is reacted with two alkyl halides…
Correct answer: Wurtz reaction- A. 3,3 4- trimethyl hexane
- B. 1,1,2- trimethyl ethane
- C. 2,2-dimethyl propane
- D. 2-ethyl,1-methylethane
Explanation: To name this first identity the longest carbon chain is 6-carbon long. Hence the name should include hexane, which is A.
Correct answer: 3,3 4- trimethyl hexane- A. Mixture of SiO2 and Ni
- B. Mixture of Pt and Cu
- C. Mixture of Fe and MgO
- D. Mixture of SiO2 and Al2O3
Explanation: A typical catalyst used for this purpose is a mixture of silica (SiO2) and alumina (AI2O3). So this is correct answer.
Correct answer: Mixture of SiO2 and Al2O3- A. A: Thermal
- B. B: Catalytic
- C. C: Steam
- D. D: Radiations
Explanation: The correct answer is Catalytic cracking, which is a preferred method for producing higher quality gasoline.
Correct answer: B: Catalytic- A. Two hydrogen atoms
- B. Three hydrogen atoms
- C. One hydrogen atom
- D. No hydrogen atom
Explanation: The central (tertiary) carbon atom in t-butyl alcohol is bonded to three methyl groups (-CH3) and a hydroxyl group (-OH).
Correct answer: No hydrogen atom- A. 2,2-Dimethyl pentane
- B. 2,3-Dimethyl pentane
- C. 2,2-Dimethyl propane
- D. 2,2-Dimethyl butane
Explanation: 2,2-Dimethyl butane is called neohexane not neopentane.
Correct answer: 2,2-Dimethyl propane- A. 2-Ethyl-3-methyl pentane
- B. 3-Ethyl-2-methyl pentane
- C. 3-Methyl cyclohexane
- D. 3-Ethyl-4-methyl pentane
Explanation: According to IUPAC nomenclature Number the longest chain, beginning with the end nearest a branch.
Correct answer: 3-Ethyl-2-methyl pentane- A. 7
- B. 6
- C. 5
- D. 4
Explanation: Hexane (C6H14) is an alkane with six carbon atoms. Alkanes are hydrocarbons with only single bonds between carbon atoms.
Correct answer: 5- A. 3-Ethyl-2-methyl pentane.
- B. 2,3-Dimethylpentane.
- C. 2,2,4-Trimethylhexane.
- D. 2,3,4-Trimethylhexane
Explanation: The correct name of the compound 3,5,5-trimethylhexane indicates that there are three methyl groups at positions 3, 5, and 5 on the hexane…
Correct answer: 2,2,4-Trimethylhexane.- A. Decrease boiling point
- B. Prevent overheating
- C. Prevent fuel from freezing
- D. Prevent knocking
Explanation: Tetraethyllead was historically used as an anti-knock agent in gasoline.
Correct answer: Prevent knocking- A. Cracking
- B. Reforming
- C. Decomposition
- D. Isomerisation
Explanation: Option A) Cracking involves breaking down large hydrocarbons into smaller ones and does not necessarily result in a higher octane…
Correct answer: Reforming- A. Ethane
- B. Propane
- C. Butene
- D. Isobutane
Explanation: When n-butane is heated in the presence of AlCl3/HCl, it undergoes a rearrangement reaction to form Isobutane.Option A (Ethane), Option B…
Correct answer: Isobutane- A. 3-ethyl-2,2,4-trimethylpentane
- B. 4-ethyl-2,2,4-trimethylpentane
- C. 5-ethyl-2,2,4-trimethylpentane
- D. 2-ethyl-2,2,4-trimethylpentane
- E. 1-ethyl-2,2,4-trimethylpentane
Explanation: The IUPAC name for the given compound (CH3)2-CH-CH(C2H5)-C(CH3)3 is "3-ethyl-2,2,4-trimethylpentane." Here's how the name is derived:1.
Correct answer: 3-ethyl-2,2,4-trimethylpentane