Preparation of Alkanes

Preparation of Alkanes MDCAT MCQs with answers

11 past paper MCQs on Preparation of Alkanes, from the Chemistry of Hydrocarbons unit of MDCAT Chemistry. The year each question appeared is shown where known; tap “Show answer” for the correct option and a short solution.

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1.The cracking method used to obtain better quality gasoline is: (NUMS MDCAT 2023)

  1. Thermal
  2. Catalytic
  3. Steam
  4. Radiations
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Correct answer: (b) Catalytic

Catalytic cracking gives branched and aromatic products, which have the higher octane number.

2.Conversion of straight chain hydrocarbons into branched chain is called as __________. (PMC MDCAT 2022)

  1. Reforming
  2. Cracking
  3. lsomerization
  4. Decomposition
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Correct answer: (a) Reforming

Reforming rearranges straight chains into branched and cyclic ones of higher octane number.

3.Which of the following fraction of petroleum has the lowest boiling point at STP. (PMC MDCAT 2022)

  1. Kerosene oil
  2. Lubricating oil
  3. Gasoline
  4. Heavy Oil
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Correct answer: (c) Gasoline

The lighter the fraction the lower it boils, and gasoline is the lightest of these.

4.Fuels with higher octane number can be produced by_ _ ? (PMC MDCAT 2022)

  1. Cracking
  2. Reforming
  3. Decomposition
  4. lsomerisation
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Correct answer: (a) Cracking

Reforming turns straight chains into branched and aromatic ones, which resist knocking.

5.The breaking of large molecules by heating at high temperature and pressure is called: (PMC MDCAT 2022)

  1. Reforming
  2. Steam cracking
  3. Catalytic cracking
  4. Thermal cracking
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Correct answer: (d) Thermal cracking

Breaking the chains by heat alone is thermal cracking.

6.Which of the following fractions of petroleum has the lowest boiling point at STP? (PMC MDCAT 2022)

  1. Kerosene Oil
  2. Lubricating Oil
  3. Gasoline
  4. Natural Gas
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Correct answer: (d) Natural Gas

Natural gas is the lightest fraction of all and boils lowest.

7.Which type of bonds are broken during cracking? (PMC Practice 2021)

  1. C- C
  2. C-H
  3. Both C-C and C-H
  4. C-0
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Correct answer: (a) C- C

Cracking breaks the chain, that is a carbon carbon bond.

8.What are the products of destructive distillation of coal? (PMC Practice 2021)

  1. Coal tar
  2. Coke
  3. Coal gas
  4. All of above
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Correct answer: (d) All of above

Heating coal out of contact with air gives coke, coal tar and coal gas.

9.Octane number of n-heptane is ______. (PMC Practice 2021)

  1. 0
  2. 100
  3. 40
  4. 98
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Correct answer: (a) 0

The octane scale is set by taking n-heptane as zero and iso-octane as a hundred.

10.What should be the temperature and pressure respectively for catalytic cracking: (UHS MDCAT 2017)

  1. 500˚C, 2 atm
  2. 900˚C, 2 atm
  3. 500˚C, 4 atm
  4. 900˚C, 4 atm
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Correct answer: (a) 500˚C, 2 atm

Catalytic cracking is done at about $500^{\circ}\mathrm{C}$ and a low pressure.

11.Which one of the following reactions shows combustion of a saturated hydrocarbon? (UHS MDCAT 2016)

  1. C2H4 + 3O2 → 2CO2 + 2H2O
  2. CH4 + 2O2 → CO2 + 2H2O
  3. CH4 + ½ O2 → CH3OH (Conditions:Cu, 400°C, 200 atm)
  4. C2H2 + 5/2 O2 → 2CO2 + H2O
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Correct answer: (b) CH4 + 2O2 → CO2 + 2H2O

Methane is the saturated one, and it burns to carbon dioxide and water.

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