Worksheet: Cracking of Hydrocarbons

In this worksheet, we will practice explaining the catalytic cracking of alkanes and its importance and describing the process on an industrial scale.

Q1:

Which type of chemical reaction is cracking an example of?

  • ACondensation
  • BAddition
  • CDisplacement
  • DHydrolysis
  • EDecomposition

Q2:

The cracking of a nonane molecule can produce a range of products.

If the cracking of a nonane molecule produces two molecules including propene, what is the name of the second product?

  • AHexane
  • BPentane
  • CPentene
  • DHeptene
  • EHexene

Which of the following pairs of molecules can be produced by the cracking of a nonane molecule, assuming there are no other products?

  • AEthene + hexene
  • BHexene + propene
  • CPropane + heptene
  • DButane + pentene
  • EOctane + methane

Which of the following groups of molecules can be produced by the cracking of a nonane molecule, assuming there are no other products?

  • APropene + propene + propene
  • BEthene + ethane + pentane
  • CHexene + propane + ethene
  • DPropane + ethene + butene
  • EButene + propane + methane

Q3:

Which of the following statements is true?

  • ACracking increases the chain length of the hydrocarbon.
  • BCracking always generates gaseous products.
  • CCracking is a method of polymerization.
  • DCracking is possible without a catalyst.
  • ECracking is exothermic.

Q4:

In which of the following properties is an increase observed when hydrocarbon fuels undergo cracking?

  • AMelting point
  • BVolatility
  • CViscosity
  • DMolecular size
  • EIgnition temperature

Q5:

In catalytic cracking, a gaseous hydrocarbon flows over a heated catalyst and is converted to more valuable products. Which of the following catalyst properties cannot be increased to produce a higher reaction rate?

  • ATemperature
  • BParticle size
  • CSurface area
  • DMass
  • EPorosity

Q6:

Cracking may be used to convert one fraction of crude oil to a mixture of hydrocarbons with the properties of a different fraction. Which of the following fuels can be replicated via the cracking of kerosene?

  • AGasoline and LPG
  • BLPG only
  • CDiesel oil and gasoline
  • DDiesel oil, gasoline, and LPG
  • EGasoline only

Q7:

In which range of temperatures is catalytic cracking usually performed?

  • A300500C
  • B0100C
  • C100300C
  • D700900C
  • E500700C

Q8:

A hydrocarbon has the structural formula shown:

The cracking of this hydrocarbon can produce a range of products.

What is the molecular formula of this hydrocarbon?

  • ACH1022
  • BCH1020
  • CCH816
  • DCH918
  • ECH818

What are the structural formulas of the products when one molecule of this hydrocarbon undergoes a single cracking reaction?

  • A
  • B
  • C
  • D
  • E

Q9:

Under which of the following conditions is thermal cracking usually performed?

  • ALow temperature and high pressure
  • BHigh temperature and low pressure
  • CHigh temperature and high pressure
  • DLow temperature and low pressure

Q10:

Shown in the equation is one possible reaction in the cracking of heptane:

+XCHHHCHCHCHHHHCCHHCHHHHHCHCHHHCHH

Compound X is an unbranched hydrocarbon. What is the displayed formula of compound X?

  • A
    CHCHCHHCHHHH
  • B
    CHCHHHHCCHHHHH
  • C
    CHHHCCHHHHH
  • D
    CCHCHHCHHHHHCHH
  • E
    CHCHHHCHHCHHHCHHH

Q11:

Cracking of compound X produces smaller molecules according to the equation shown:

Compound X is an unbranched hydrocarbon. What is the displayed formula of compound X?

  • A
  • B
  • C
  • D
  • E

Q12:

During catalytic cracking of a hydrocarbon mixture, a molecule X reacts according to the equation shown:

Which of the following is a possible structural formula for the reacting molecule?

  • A
  • B
  • C
  • D
  • E

Q13:

In a cracking reaction, a hydrocarbon with molecular formula CH1838 is converted to two liquid compounds A and B. The displayed formula of A is as shown:

What is the molecular formula of A?

  • ACH1124
  • BCH1024
  • CCH1122
  • DCH1224
  • ECH1226

What is the molecular formula of B?

  • ACH714
  • BCH612
  • CCH614
  • DCH716
  • ECH814

Which of the following properties is the least useful for distinguishing between compounds A and B?

  • AIgnition temperature
  • BSmell
  • CMelting temperature
  • DReaction with bromine water
  • EColor

Q14:

In a cracking reaction, tetradecane (CH)1430 is converted into three compounds. The molecular formulas of two of these compounds are CH48 and CH716.

What is the name of the third product?

  • AEthane
  • BPropene
  • CEthene
  • DButene
  • EPropane

What is the molecular formula of the third product?

  • ACH24
  • BCH38
  • CCH48
  • DCH36
  • ECH26

What is the displayed formula of the third product?

  • A
    CHHCHH
  • B
    CHHCHHCHHHH
  • C
    CHHCCHHHH
  • D
    CHHHCHHH
  • E
    CHHCHCCHHHHH

Q15:

A molecule of dodecane (CH)1226 can undergo multiple cracking reactions to produce many smaller molecules. Three possible products are compounds AC, which have the shown structural formulas.

How many molecules of A can be produced by the cracking of a dodecane molecule?

How many molecules of B can be produced by the cracking of a dodecane molecule?

How many molecules of C can be produced by the cracking of a dodecane molecule?

Q16:

A hydrocarbon molecule has the molecular formula CH3062 and can be converted into a mixture of many smaller hydrocarbon molecules via cracking reactions.

The cracking of 1 molecule of the hydrocarbon is found to produce 4 molecules of butene, 2 molecules of propene, and 1 molecule of a different compound X. No other product molecules are present. What is the molecular formula of compound X?

  • ACH1020
  • BCH1022
  • CCH818
  • DCH1226
  • ECH1224

The cracking of 1 molecule of the hydrocarbon is found to produce 1 molecule of butane, 7 molecules of ethene, and 4 molecules of a different compound Y, which decolorizes bromine water. Other product molecules may be present. What is the structural formula of compound Y?

  • A
    CHCHCHHHH
  • B
    CHHHH
  • C
    CHCHHHHH
  • D
    CCHHHH
  • E
    CCHHHHHCHHH

Which of the following groups of molecules could be produced by the cracking of this hydrocarbon?

  • A2CH+CH+2CH91848510
  • B2CH+CH+CH102061248
  • C3CH+2CH+2CH61241226
  • D3CH+3CH+CH51036716
  • E3CH+CH+2CH71451224

Q17:

Cracking of a liquid alkane can be performed in a sealed vessel containing pieces of pottery.

Which types of compound are produced by this reaction?

  • AAlkanes only
  • BAlkanes and alkenes
  • CAlkenes only
  • DAlkanes and alkynes
  • EAlkynes only

Which physical process must the alkane undergo prior to the cracking reaction?

  • ADissolution in alcohol
  • BDissolution in water
  • CFreezing
  • DMelting
  • EVaporization

Which change to the conditions in the flask is most crucial for ensuring a high reaction rate?

  • ARemoving oxygen from the air
  • BLowering the pressure
  • CHeating the pottery
  • DDrying the air
  • EPowdering the pottery

What is the function of pottery in this reaction?

  • AIncreasing the rate of the reaction
  • BBinding by-products of the reaction
  • CPreventing combustion of the alkane
  • DImproving heat transfer to the alkane
  • EProviding hydrogen for the reaction

Q18:

What is the best description for the cracking process?

  • ACracking is a thermal decomposition reaction that breaks large hydrocarbon molecules into more useful shorter ones.
  • BCracking is a distillation process that separates hydrocarbons into alkanes and corresponding alkenes.
  • CCracking is a dehydrogenation process that forms alkenes as a main product.
  • DCracking is a thermal decomposition reaction that breaks large hydrocarbon molecules into alkenes and corresponding alkynes.
  • ECracking is a dehydration process that forms alkenes as a main product.

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