Cracking and alkenes

Alkanes and alkenes are hydrocarbons.

Hydrocarbon molecules are made up of hydrogen and carbon atoms only.

An alkene has the formula C₃H₆

Which alkene has the formula C₃H₆?

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How many atoms are there in a molecule of C₃H₆?

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Which is a use of C₃H₆?

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The percentage (%) by mass of each element in a molecule of C₃H₆ is:

hydrogen 14%

carbon 86%.

Figure 1 shows the percentage by mass of hydrogen in a molecule of C₃H₆

Complete Figure 1.

You should:

• complete the y-axis scale

• plot the percentage by mass of carbon as a bar

• label the bar plotted for carbon.

Alkanes can be cracked to produce alkenes and smaller alkane molecules.

Describe a test for alkenes.

Give the result of the test.

C₁₀H₂₂ can be cracked to produce C₃H₆ and an alkane.

Complete the equation for the reaction.

Complete the sentence.

Choose the answer from the box.

ceramics fertilisers fuels

High temperatures between 450 °C and 750 °C are used in cracking reactions.

Which statement describes the molecules at 750 °C compared with the molecules at 450 °C?

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How does the rate of reaction at 750 °C compare with the rate of reaction at 450 °C?

This question is about monomers and polymers.

Compound A has an alkene functional group and an ester functional group.

Figure 8 represents a molecule of compound A.

Draw a circle around the alkene functional group on Figure 8.

Describe what will be seen when compound A is shaken with bromine water.

Figure 9 is a repeat of Figure 8.

Draw a circle around the ester functional group on Figure 9.

Compound A has the formula C₄H₆O₂

Compound A is flammable.

Write a balanced equation for the complete combustion of compound A.

Many molecules of compound A join together to form polymer B.

Complete the displayed formula equation which represents this reaction.

What type of polymer is polymer B ?

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Polymer B is a polymer which melts when heated.

What word is used to describe polymers which melt when heated?

Explain why some polymers do not melt when heated.

This question is about hydrocarbons in crude oil.

Table 2 shows information about three fractions obtained from crude oil.

Figure 1 shows the fractionating column used to separate fractions A, B and C.

The temperature of the fractionating column is:

• 30 °C at the top

• 400 °C at the bottom.

Complete Figure 1 to show where fractions A, B and C are collected.

Table 3 shows information about three fractions obtained from crude oil.

Complete the sentences. Choose answers from the box.

Table 4 shows the percentage of two fractions obtained from two different sources of crude oil.

Complete Figure 2. You should:

• complete the y-axis scale

• plot the percentage of the heavy fuel oil fraction obtained from source K.

Use Table 4.

Kerosene is in higher demand than heavy fuel oil. Suggest why crude oil from source J is in higher demand than crude oil from source K. Use Table 4.

Large hydrocarbon molecules can be cracked to produce smaller hydrocarbon molecules including alkanes.

Which two of the following can be used to crack large hydrocarbon molecules? Tick (✓) two boxes.

Alkanes have the general formula C_nH_2n+2 Complete the formula of the alkane molecule containing 11 carbon atoms.

C₂H₆ is an alkane. Which type of bond is found in a C₂H₆ molecule? Tick (✓) one box.

Which two substances are produced when alkanes completely combust? Tick (✓) two boxes.

This question is about the fractions obtained from crude oil.

Crude oil is separated into fractions by fractional distillation. The fractions obtained from crude oil include:

• lubricating oil

• naphtha

• petroleum gases.

Table 3 shows the boiling point range of these fractions.

Explain how these fractions are obtained from crude oil by fractional distillation.

Fractions from crude oil can be processed to produce feedstock for the petrochemical industry. Which two are useful materials produced from this feedstock? Tick (✓) two boxes.

Another fraction obtained from crude oil is petrol.

Petrol contains a hydrocarbon with the formula C₉H₂₀ Complete the equation for the complete combustion of C₉H₂₀ You should balance the equation.

Petrol obtained from crude oil contains sulfur impurities. Explain why sulfur impurities are removed before petrol is burned in car engines.

Table 4 shows information about two more fractions obtained from crude oil.

A student predicted that heavy fuel oil is more viscous than kerosene. The student’s prediction was correct.

Justify the student’s prediction.

The heavy fuel oil fraction can be processed to produce smaller hydrocarbon molecules.

Name the process which produces smaller hydrocarbon molecules from heavy fuel oil. Give the conditions used in this process.

Hydrocarbon molecules containing seven and eight carbon atoms can be produced when heavy fuel oil is processed. Which pair of hydrocarbon molecules would both turn bromine water colourless? Tick (✓) one box.

This question is about cycloalkenes. Cycloalkenes are ring-shaped hydrocarbon molecules containing a double carbon-carbon bond. Cycloalkenes react in a similar way to alkenes.

Describe a test for the double carbon-carbon bond in cycloalkene molecules. Give the result of the test.

Table 3 shows the name and formula of three cycloalkenes.

Determine the general formula for cycloalkenes.

Figure 6 shows the displayed structural formula of cyclohexene, C₆H₁₀

Chlorine reacts with cyclohexene to produce a compound with the formula C₆H₁₀Cl₂

Complete Figure 7 to show the displayed structural formula of C₆H₁₀Cl₂

Figure 7

Calculate the percentage by mass of chlorine in a molecule of C₆H₁₀Cl₂ Relative atomic masses (A_r): H = 1 C = 12 Cl = 35.5

This question is about alkenes and alcohols. Ethene is an alkene produced from large hydrocarbon molecules. Large hydrocarbon molecules are obtained from crude oil by fractional distillation.

Name the process used to produce ethene from large hydrocarbon molecules.

Describe the conditions used to produce ethene from large hydrocarbon molecules.

Ethanol can be produced from ethene and steam. The equation for the reaction is:

The forward reaction is exothermic.

Explain how the conditions for this reaction should be chosen to produce ethanol as economically as possible.

Ethanol can also be produced from sugar solution by adding yeast. Name this process.

Butanol can be produced from sugar solution by adding bacteria. Sugar solution is broken down in similar ways by bacteria and by yeast. Suggest the reaction conditions needed to produce butanol from sugar solution by adding bacteria.

Ethanol and butanol can be used as fuels for cars.

A car needs an average of 1.95 kJ of energy to travel 1 m Ethanol has an energy content of 1300 kilojoules per mole (kJ/mol). Calculate the number of moles of ethanol needed by the car to travel 200 km

When butanol is burned in a car engine, complete combustion takes place. Write a balanced equation for the complete combustion of butanol. You do not need to include state symbols.

This question is about materials used to make plates.

Plates are made from ceramics, paper or poly(propene).

Paper plates are biodegradable and recyclable.

Which stage of a life cycle assessment (LCA) would contain this information?

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Which two processes are used to make ceramic plates?

Tick (✓) two boxes.

Poly(propene) is produced from an alkene.

Complete the sentences.

The alkene needed to make poly(propene) is produced from crude oil.

Which two processes are used to produce this alkene from crude oil?

Tick (✓) two boxes.

What type of bond joins the atoms in a molecule of poly(propene)?

Tick (✓) one box.

Table 4 shows information about two polymers used to make plates.

What type of polymer is polymer A ?

Use Table 4.

Why does polymer A behave differently to polymer B when heated?

You should refer to crosslinks in your answer.

This question is about hydrocarbons.

Hexane and hexene are hydrocarbons containing six carbon atoms in each molecule.

Hexane is an alkane and hexene is an alkene.

Draw one line from each hydrocarbon to the formula of that hydrocarbon.

Bromine water is added to hexane and to hexene.

What would be observed when bromine water is added to hexane and to hexene?

Ethane is an alkane and ethene is an alkene.

Figure 8 shows the displayed structural formulae of ethane and of ethene.

Compare ethane with ethene.

You should refer to:

• their structure and bonding

• their reactions.

This question is about hydrocarbons. Hexane and hexene are hydrocarbons containing six carbon atoms in each molecule. Hexane is an alkane and hexene is an alkene.

Draw one line from each hydrocarbon to the formula of that hydrocarbon.

Bromine water is added to hexane and to hexene. What would be observed when bromine water is added to hexane and to hexene?

Ethane is an alkane and ethene is an alkene. Figure 1 shows the displayed structural formulae of ethane and of ethene.

Compare ethane with ethene. You should refer to:

• their structure and bonding

• their reactions.

Titan is a moon of the planet Saturn.

Table 2 shows the percentages of some gases in the atmosphere of Titan and in the atmosphere of the Earth.

Which two gases are present in smaller percentages on the Earth than on Titan?

Complete the bar chart in Figure 2 to show the percentages of nitrogen gas and oxygen gas in the Earth’s atmosphere.

Why are algae less likely to photosynthesise on Titan than Earth?

Use Table 2.

Tick (✓) one box.

Titan is warmer than the other moons of Saturn because of the greenhouse effect.

How do greenhouse gases trap energy from the sun?

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As well as methane, the atmosphere of Titan contains small amounts of propene gas. Methane is an alkane and propene is an alkene.

Bromine water is an orange solution used to identify alkenes.

Draw one line from each gas to its effect on bromine water.

Propene reacts with water (steam) to make propanol.

The ratio of the masses of propene and water that react is:

propene: water

7: 3

Calculate the mass of propene that reacts with 21 g water.

This question is about crude oil and hydrocarbons.

Figure 6 shows a fractionating column used to separate crude oil into fractions.

Table 5 gives information about some of the fractions.

Suggest a suitable temperature for the furnace in Figure 6.

Explain why diesel oil collects above heavy fuel oil but below kerosene in the fractionating column.

Use Table 5.

Suggest two reasons why bitumen is not used as a fuel.

Petrol contains mainly alkanes.

Which of the following compounds is an alkane?

Tick (✓) one box.

Large hydrocarbon molecules in the diesel oil fraction are cracked to produce smaller hydrocarbon molecules.

Describe the conditions needed to crack hydrocarbon molecules from the diesel oil fraction.

Explain why large hydrocarbon molecules in the diesel oil fraction are cracked to produce smaller hydrocarbon molecules.

Complete the equation for the cracking of C₁₅H₃₂

This question is about crude oil and hydrocarbons.

Figure 1 shows a fractionating column used to separate crude oil into fractions.

Table 1 gives information about some of the fractions.

Suggest a suitable temperature for the furnace in Figure 1.

Explain why diesel oil collects above heavy fuel oil but below kerosene in the fractionating column.

Use Table 1.

Suggest two reasons why bitumen is not used as a fuel.

Petrol contains mainly alkanes.

Which of the following compounds is an alkane?

Tick (✓) one box.

Large hydrocarbon molecules in the diesel oil fraction are cracked to produce smaller hydrocarbon molecules.

Describe the conditions needed to crack hydrocarbon molecules from the diesel oil fraction.

Explain why large hydrocarbon molecules in the diesel oil fraction are cracked to produce smaller hydrocarbon molecules.

Complete the equation for the cracking of C₁₅H₃₂

Titan is a moon of the planet Saturn.

Table 3 shows the percentages of the gases in the atmosphere of Titan.

Some scientists think that living organisms could have evolved on Titan.

Explain why these organisms could not have evolved in the same way that life is thought to have evolved on Earth.

Use Table 3.

Saturn has other moons.

The other moons of Saturn have no atmosphere.

Titan is warmer than the other moons of Saturn because its atmosphere contains the greenhouse gas methane.

Explain how this greenhouse gas keeps Titan warmer than the other moons of Saturn.

The atmosphere of Titan contains small amounts of propene.

Describe a test to show that propene is an unsaturated hydrocarbon.

Give the result of the test.