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 1 of 7
- A. their carbon to hydrogen bonds are strong and almost non polar, offering nothing for a nucleophile or electrophile to attack
- B. they contain a double bond
- C. they are ionic compounds
- D. they have very high molar masses
Explanation: Carbon and hydrogen have similar electronegativities, so the bonds carry almost no dipole and there is no region of high or low electron…
Correct answer: their carbon to hydrogen bonds are strong and almost non polar, offering nothing for a nucleophile or electrophile to attack- A. sp
- B. sp2
- C. sp3
- D. unhybridised p
Explanation: Four sigma bonds require four equivalent orbitals, so one s and three p orbitals mix to give four sp3 hybrids pointing to the corners of a…
Correct answer: sp3- A. CnH2n
- B. CnH2n-2
- C. CnH2n+2
- D. CnH2n+1
Explanation: Every carbon in a saturated open chain carries the maximum hydrogen, giving two per carbon plus two extra for the ends of the chain, so…
Correct answer: CnH2n+2- A. the covalent bonds within the molecules become stronger
- B. the molecules become more polar
- C. hydrogen bonding develops between longer chains
- D. the larger surface area increases the dispersion forces between molecules
Explanation: Longer chains touch each other over a greater area, so the temporary induced dipole attractions between molecules add up to more, and more…
Correct answer: the larger surface area increases the dispersion forces between molecules- A. produce shorter, more useful alkanes and alkenes for fuel and plastics
- B. remove sulphur from crude oil
- C. convert alkenes into alkanes
- D. increase the molar mass of the products
Explanation: Fractional distillation yields more of the heavy fractions than the market wants and too little petrol, so cracking breaks the long chains…
Correct answer: produce shorter, more useful alkanes and alkenes for fuel and plastics- A. Ethane
- B. Methane
- C. Propane
- D. Butane
Explanation: Methane, CH4, is called marsh gas because it is produced by the anaerobic decomposition of organic matter in marshes and swamps.
Correct answer: Methane- A. Alkanes
- B. Alkynes
- C. Alkenes
- D. a & c
Explanation: Aliphatic hydrocarbons containing only carbon-carbon single covalent bonds are saturated hydrocarbons called alkanes, with the open-chain…
Correct answer: Alkanes- A. C4H6
- B. C5H12
- C. C3H4
- D. C6H10
Explanation: C5H12 fits the alkane formula CnH2n+2 because 2(5) + 2 = 12, so it is saturated rather than unsaturated.
Correct answer: C5H12- A. iso-octane
- B. n-hexane
- C. n-heptane
- D. iso-heptane
Explanation: The octane scale assigns 0 to n-heptane and 100 to iso-octane because these compounds represent the reference extremes for knocking…
Correct answer: n-heptane- A. (C2H5 )4Pb
- B. TNT
- C. CH MgBr3
- D. C2H5 )2Hg
Explanation: Tetraethyl lead, (C2H5)4Pb, was added to petrol as an antiknock agent because it reduced premature ignition and engine knocking.
Correct answer: (C2H5 )4Pb- A. 20% n- heptane + 80% iso-octane
- B. 80% n- heptane + 20% iso-octane
- C. 20% n- heptane + 80% n-octane
- D. 80% n-heptane + 20% n- octane
Explanation: An octane number of 80 means the petrol has the same knocking tendency as a mixture containing 80% iso-octane and 20% n-heptane by volume.
Correct answer: 20% n- heptane + 80% iso-octane- A. NH3
- B. CH4
- C. CO2
- D. C6H6
Explanation: Methane is the simplest alkane and has one carbon atom bonded to four hydrogen atoms, so its formula is CH4.
Correct answer: CH4- A. octane number
- B. Heptane number
- C. Reforming
- D. Refining
Explanation: Petrol quality for spark-ignition engines is expressed by its octane number, which measures resistance to knocking compared with standard…
Correct answer: octane number- A. Reforming
- B. Induction fueling
- C. Cracking
- D. Refining
Explanation: Cracking breaks large, less useful hydrocarbons into smaller hydrocarbons, including petrol-range molecules, so it increases the quantity…
Correct answer: Cracking- A. Coal Tar
- B. Coal gas
- C. Coke
- D. None of These
Explanation: Coke is the solid carbon-rich residue obtained by destructive distillation of coal and contains mostly carbon.
Correct answer: Coke- A. Refining
- B. Cracking
- C. Reforming
- D. None of These
Explanation: Catalytic reforming converts straight-chain hydrocarbons into branched, cyclic and aromatic hydrocarbons, which resist knocking and…
Correct answer: Reforming- A. Reforming
- B. Cracking
- C. Refining
- D. Isomerization
Explanation: Cracking is the thermal or catalytic decomposition of large hydrocarbon molecules into smaller alkanes and alkenes.
Correct answer: Cracking- A. Cracking
- B. Reforming
- C. Refining
- D. Hydration
Explanation: Reforming improves petrol quality by converting straight-chain hydrocarbons into branched, cyclic and aromatic compounds with better…
Correct answer: Reforming- A. Hydrogen & Water
- B. Hydrogen & Carbon dioxide
- C. Hydrogen & Methane
- D. Carbonmonoxdide & water
Explanation: Coal gas is produced by the destructive distillation of coal and contains hydrogen, methane, carbon monoxide and other gases, with…
Correct answer: Hydrogen & Methane- A. Methane
- B. Ethane
- C. Hydrogen
- D. Nitrogen
Explanation: Marsh gas is methane, CH4, because methane was historically collected from marshes during the decomposition of plant material under…
Correct answer: MethaneAlkanes MCQs: common questions
Are these Alkanes MCQs free?
Yes. All Alkanes MCQs from Chemistry are free on TestUstad, with unlimited attempts and no account needed. Nothing on this page is a sample or a trial.
How many Alkanes MCQs are on this page?
There are 127 Alkanes MCQs in the Chemistry bank, shown 20 to a page with the correct answer and an explanation on each.
Does every Alkanes MCQ have an explanation?
Yes. Each Alkanes question shows the correct option and a written explanation of why it is correct, so a wrong answer teaches you something rather than just being marked wrong.
Can I take a timed Alkanes test?
Yes. The practice button on this page starts a free Alkanes test drawn from the Chemistry bank. It marks each answer instantly, gives you a score at the end, and can be retaken as many times as you like.