Cracking & alkenes

Hydrocarbons in crude oil are separated into fractions using fractional distillation.

Figure 8 shows a fractional distillation column.

What is the name of the process that produces the diesel oil fraction at Z on Figure 8 ?

Tick () one box.

Condensing

Freezing

Melting

Different hydrocarbons have different-sized molecules.

Crude oil contains different percentages of each fraction.

Table 4 shows information about petrol and heavy fuel oil.

The supply of petrol is not enough to meet the demand for petrol.

The additional petrol needed can be produced by cracking other fractions.

Cracking breaks down larger molecules into smaller molecules.

Give two reasons why heavy fuel oil is a suitable fraction to be cracked to produce petrol.

The products of cracking include another type of hydrocarbon called alkenes.

Small alkene molecules can join together to produce long-chain molecules.

What type of reaction produces long-chain molecules?

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Decomposition

Oxidation

Polymerisation

Plastics are produced from alkenes.

Drinks can be sold in plastic bottles or glass bottles.

Table 5 shows information about some plastic bottles and some glass bottles.

Explain why less energy is used to transport the same volume of liquid in plastic bottles than in glass bottles.

Some plastic bottles are disposed of as waste in landfill sites.

Suggest two ways that people can reduce the environmental impact of plastic bottles.

This question is about cracking and the products of cracking.

Alkane molecules are often cracked.

Describe the conditions needed for cracking.

Explain how cracking alkane molecules helps to meet the demand for fuels.

The products of cracking include another type of hydrocarbon called alkenes.

Give one use of alkenes.

Do not refer to the use of alkenes as fuels.

Ethene is an alkene.

Figure 11 represents the reaction of ethene with chlorine.

Figure 11

Table 2 shows some bond energy values.

Calculate the overall energy change for the reaction of ethene with chlorine.

_ Overall energy change = ________________ kJ/mol

This question is about hydrocarbons.

Name the two elements in a hydrocarbon.

Which two of the following substances are hydrocarbons?

Tick (✓) two boxes.

Ammonia

Ethene

Graphite

Methane

Steam

C₆H₁₄ is a hydrocarbon.

C₆H₁₄ can be broken down into smaller molecules.

Complete the equation for the breakdown of C₆H₁₄ into smaller molecules.

What is the name of the process t hat breaks d own C₆H₁₄ into smaller molecules?

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Cracking

Distillation

Neutralisation

How does the boiling point of C₆H₁₄ compare with the boiling point of C₄H₁₀?

Give one reason for your answer.

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C₆H₁₄ has a lower boiling point.

C₆H₁₄ and C₄H₁₀ have the same boiling point.

C₆H₁₄ has a higher boiling point.

The complete combustion of C₆H₁₄ produces water and one other product.

Name the other product of the complete combustion of C₆H₁₄

Do not refer to water in your answer.

The formula of water is H₂O

Calculate the relative formula mass (M_r) of water.

Relative atomic masses (A_r): H = 1 O = 16

This question is about hydrocarbons.

Hexane (C₆H₁₄) and pentane (C₅H₁₂) are hydrocarbons in the same homologous series.

Give the name of the homologous series that includes hexane and pentane.

Give the general formula of the homologous series that includes hexane and pentane.

Explain why the boiling point of hexane is higher than the boiling point of pentane.

Complete the equation for the cracking of hexane (C₆H₁₄) into ethene and one other molecule.

Methane undergoes complete combustion with oxygen.

Figure 10 represents the equation for the reaction.

Figure 10

The energy released forming the new bonds is 814 kJ/mol greater than the energy needed to break the existing bonds.

Table 4 shows some bond energy values.

Calculate value Y in Table 4.

_ Y = ____________________ kJ/mol

This question is about hydrocarbons.

Methane is a hydrocarbon.

The formula of methane is CH₄

Name the two elements in methane.

Complete Figure 5 to show the structure of a methane (CH₄) molecule.

Figure 5

H ‒ C

What is the type of bonding in methane?

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Covalent

Ionic

Metallic

Calculate the percentage by mass of element C in a CH₄ molecule.

Relative atomic mass (A_r): C = 12

Relative formula mass (M_r): CH₄ = 16

Cracking breaks down hydrocarbons into smaller molecules.

Name one method of cracking.

C₁₃H₂₈ is a hydrocarbon.

C₁₃H₂₈ is cracked to produce C₈H₁₈ and another product.

Complete the equation for the reaction.

C₈H₁₈ and C₁₃H₂₈ are both alkanes.

C₈H₁₈ is a smaller molecule than C₁₃H₂₈

Give one use of alkanes that have small molecules.

Cracking also produces alkenes.

Ethene is an alkene.

What is the formula of ethene?

Tick (✓) one box.

C₂H₄ C₂H₆ C₃H₆ C₃H₈

This question is about carbon and carbon compounds.

Carbon forms compounds called alkanes.

Which formula represents an alkane molecule with 8 carbon atoms?

Tick (✓) one box.

C₈H₁₀

C₈H₁₄

C₈H₁₆

C₈H₁₈

Alkanes can be cracked.

Name one method of cracking alkanes.

Explain how cracking alkanes helps to meet the demand for fuels.

Ethene can be produced when alkanes are cracked.

The formula of ethene is C₂H₄

Calculate the simplest whole number ratio by mass of carbon to hydrogen in ethene.

Relative atomic masses (A_r): C = 12 H = 1

Ratio by mass of carbon: hydrogen = ______________: ______________

Carbon exists in different forms.

Which form has each carbon atom bonding with four other carbon atoms?

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Diamond

Graphene

Graphite

Fullerene molecules are made of carbon atoms.

Give two other features of the structure of fullerene molecules.

A carbon nanotube has:

a length to diameter ratio of 6 900 000: 1

Calculate the length of the carbon nanotube in nm.

Explain why carbon nanotubes are good conductors of electricity.

This question is about hydrocarbons.

When a hydrocarbon C₁₀H₂₂ is cracked, two substances are produced.

Complete the equation for the reaction.

Explain why the hydrocarbon C₇H₁₆ has a lower boiling point than C₁₀H₂₂

Ethanol is produced by reacting ethene with steam.

The equation for the reaction is:

Figure 4 shows the percentage yield of ethanol using different reaction conditions.

Explain why changing the pressure affects the percentage yield of ethanol.

The forward reaction is exothermic.

How does Figure 4 provide evidence for this?

Figure 5 shows part of a reaction profile diagram.

A catalyst is used in the reaction to produce ethanol.

Complete Figure 5 to show how the catalyst increases the rate of this reaction.

You should label the reaction profile diagram.

Suggest why the catalyst does not affect the yield of ethanol at equilibrium.