Edexcel GCSE Chemistry

Topic Questions

8.1 Fuels

1a2 marks

The structure of a molecule of propane is shown as

propane

Give the names of the elements combined together in propane.
1b3 marks

Propane can burn completely in oxygen to form carbon dioxide and water.

i)
Write the word equation for this reaction.

(2)

ii)
Propane is a fuel.

Give the reason why fuels are burned.

(1)

1c1 mark

Which product is formed when there is incomplete combustion of propane?

  A sulfur dioxide
  B oxygen
  C hydrogen
  D carbon monoxide

1d1 mark

Which of the following is the formula of a hydrocarbon?

  A C6H5OH
  B CH2OHCH2OH
  C H2C=CHCH2CH3
  D C6H12Cl2

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2a1 mark

Crude oil is a mixture of organic compounds.
Most of these compounds are saturated hydrocarbons from the same homologous series.

State the name of this homologous series.

2b4 marks

An industrial process is used to separate crude oil into fractions.

 
i)
The process depends on a difference in a property of the fractions.
What is this property?

  A boiling point
  B density
  C flammability
  D melting point 

(1)

ii)
The boxes give some uses of fractions and some names of fractions.
 
Draw one straight line from each use to its correct fraction.
1cr-q3

(3)

2c2 marks

Fuels obtained from the fractions may contain impurities including sulfur.

Explain how the combustion of sulfur in fuels may cause an environmental problem.

2d4 marks

Some of the fractions contain long-chain molecules which are not very useful.

 
i)
Give the name of the process used to convert long-chain molecules into more useful shorter-chain molecules.
 
(1)
 
ii)
Name the catalyst used in the industrial process to convert long-chain molecules into shorter-chain molecules.
 
(1)
 
iii)
When C13H28 is used in this process, three different molecules are formed.

Complete the equation for this reaction.
 
C13H28  →  C8H18  +  C3H__  +  C__H4
(2)

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3a5 marks

Fuels are combusted to release some of the chemical energy stored within their molecules. The combustion of fuels produces a variety of chemicals.

Complete the sentences to describe the two different types of combustion.

 

____________________ combustion occurs with a ____________________ supply of oxygen forming carbon dioxide and water.

 

____________________ combustion occurs with a ____________________ supply of oxygen forming carbon ____________________, carbon and water.

3b4 marks

The different products of combustion can be attributed to different issues.

Match the combustion product to its associated issue.

You must only draw one line from each combustion product.

  
combustion-problems-matchup-q
3c2 marks

Most vehicles now have catalytic converters to remove various pollutants. The most common transition metals used in catalytic converters are platinum, palladium and rhodium, which are all relatively expensive.

Explain how these metals are used inside a catalytic converter despite their cost.

3d2 marks

Over recent years, the use of hydrogen as a fuel has increased with an estimated 5% increase in the worldwide demand for hydrogen between 2020 and 2021.

State one advantage and one disadvantage of the use of hydrogen as a fuel.

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4a1 mark

Sulfur dioxide and oxides of nitrogen are two common pollutants. 

Nitrogen has an atomic number of 7.

Complete the electronic structure of nitrogen.

 _ECPO~F8_shells-

4b3 marks

In a car engine, oxides of nitrogen are released into the atmosphere.

Complete the sentences using the words in the box to help you. 

high poisoning nitrogen global warming
nitric acid low carbon dioxide oxygen global dimming

Oxides of nitrogen are produced when nitrogen reacts with .............................. in the air.

This reaction occurs at   ............................ temperatures.

Oxides of nitrogen cause   ............................

4c1 mark

Sulfur dioxide is formed when energy is released from burning a fuel.

Which reaction releases energy from a fuel?

  A Respiration
  B Combustion
  C Neutralisation
  D Decomposition

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5a2 marks

Crude oil is a mixture of hydrocarbons which can be separated into useful fractions by fractional distillation. 

Figure 1 shows a fractional distillation column and the fractions produced when crude oil is distilled. 

kG-jL2x7_fractional-distillation

Figure 1

i)
Name the fraction used in domestic heating. 
(1)
ii)
Name the fraction that contains hydrocarbons with the highest boiling point. 
(1)

5b1 mark

When crude oil is fractionally distilled, the demand for some fractions is greater than the amount produced. 

The relative amounts of each fraction in crude oil and the relative demand for each one is shown in Figure 2. 

fraction relative amount relative demand
gases 3 7
petrol 13 30
kerosene 17 10
diesel oil 25 30
fuel oil 38 22
bitumen  10 5

Figure 2

Which of the following shows the fractions where the relative amount is greater than the relative demand in the crude oil?

  A kerosene, diesel oil, bitumen
  B bitumen, petrol, gases 
  C fuel oil, bitumen, kerosene 
  D gases, petrol, diesel oil

5c1 mark

Some of the fractions produced from fractional distillation can be broken down into smaller hydrocarbons by cracking. 

Decane, C10H22, can be cracked to produce one molecule of ethene, ,  and one molecule of CXH18.

C10H22  →   C2H4   +    CXH18   

Determine the value of x in the molecule CXH18.

5d2 marks

Describe a test you could to distinguish between the alkane and alkene produced in part c). 

Give the result of this test. 

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1a3 marks

An impure hydrocarbon fuel is burned in the apparatus in Figure 1.

fig-7-q9a-1cho-2h-paper-1-nov-2020

Figure 1

When the fuel is burned

  • the funnel becomes hot
  • a colourless liquid forms in tube A
  • the indicator in tube B changes colour to show an acidic gas.

Explain these observations.

1b
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4 marks

Higher Only

The energies of some bonds are shown in Figure 2.

bond bond energy in kJmol-1
begin mathsize 14px style straight C long dash straight H end style 435
straight O equals straight O 496
begin mathsize 14px style straight C equals straight O end style 805
straight H long dash straight O 463

Figure 2

Methane burns in oxygen to form carbon dioxide and water.

The equation shows the structures of the molecules.

fig-q9-1cho-2h-paper-1-nov-2020

Calculate the energy change, in kJ mol-1, for this reaction.

energy change = .................................. kJ mol-1

1c6 marks

Petrol and diesel are used as fuels for cars.
The emissions from three similar sized cars were investigated.
The first car was the oldest, had no catalytic converter and used petrol.
The other two cars were only a few years old.
One of these was fitted with a catalytic converter and used petrol and the other car used diesel.

Figure 9 shows the emissions in grams for each kilometre travelled by these three cars.

  emissions in gkm-1
carbon
monoxide
nitrogen
oxides
carbon
dioxide
carbon
particulates
car with no catalytic converter using petrol 1.60 0.09 180 0.00
car with catalytic converter using petrol 0.67 0.02 180 0.00
car using diesel 0.05 0.19 130 0.02

Figure 3

Discuss and compare the impact on the environment of the emissions from these three cars using the information from Figure 9.

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2a4 marks

Pentadecane, C15H32, is a hydrocarbon and is used as a fuel.

The incomplete combustion of pentadecane produces carbon monoxide.
 Carbon monoxide is a toxic gas.
i)
Explain why the incomplete combustion of pentadecane can produce carbon monoxide as one of the products.
(2)
ii)
Explain how carbon monoxide behaves as a toxic gas.

(2)

2b1 mark

1 mole of pentadecane can be cracked to form 1 mole of octane, C8H18, and 1 mole of propene, C3H6, and 2 moles of another product.

Complete the balanced equation for this reaction by adding the formula of the missing product.

C15H32 → C8H18 + C3H6 + 2 ..................................

2c
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3 marks

Higher Only

Figure 1 shows the reaction of propene, C3H6, with water.

fig-11-q9c-1cho-2h-paper-1-nov-2021

Figure 1

Figure 12 shows some bond energies.

bond bond energy in kJ mol-1
straight C long dash straight C 347
straight C long dash straight O 358
begin mathsize 14px style straight C long dash straight H end style 413
straight O long dash straight H 464
begin mathsize 14px style straight C equals straight C end style  612

Figure 2

Use the bond energies in Figure 2 to calculate the energy change of the reaction in Figure 1.

energy change of reaction = ................................ kJ mol-1

2d2 marks

Methane gas, CH4, was burned using the apparatus shown in Figure 3.

fig-13-q9d-1cho-2h-paper-1-nov-2021

Figure 3

Explain why water droplets form on the bottom of the beaker of cold water.

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3a4 marks

This question is about the processes and reactions which occur in the petrochemical industry. 

Figure 1 shows some of these processes and reactions. 

 

aqa-gcse-7-1h-tq1a-petrochemical-industry-processes

Figure 1

Describe how crude oil is separated into fractions.

3b3 marks
i)
Name the process that occurs in reactor 1.
(1)
ii)
Explain why this process is carried out.
(2)

3c1 mark

Name the reaction that occurs in reactor 2. 

3d4 marks

Compare the properties of gasoline and fuel oil.

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4a4 marks

This question is about pollutants.

Fossil fuels, such as coal, are burned to release energy.

Hydrogen, sulfur, and carbon are all elements found in coal.

Name two products released when coal burns that have a negative effect on the environment.

State the impact each of the products you have named have.

4b2 marks

Oxides of nitrogen also impact the environment.

Explain how oxides of nitrogen are formed in car exhausts. 

4c2 marks

Describe two effects of oxides of nitrogen being released into the atmosphere.

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5a2 marks

Hydrogen can be used as an alternative to petrol in cars. 

One method of utilising this is in hydrogen-oxygen fuel cells. 

Write the balanced symbol equation for the overall reaction which occurs in a hydrogen-oxygen fuel cell. 

5b2 marks

The General Motors Electrovan was built in 1966. It was the first vehicle powered by a hydrogen fuel cell and could travel at up to 70 mph for 30 seconds.

Suggest two environmental advantages of using a hydrogen fuel cell rather than an internal combustion engine.

5c1 mark

Hydrogen fuel cells are commonly considered to be carbon neutral by the general public because they do not release any carbon dioxide or other greenhouse gases when they are used. This is not technically correct.

Suggest why hydrogen fuel cells cannot be classed as carbon neutral.

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11 mark

Which molecule can be cracked to produce hexane, C6H14? 

  A C4H8
  B C4H10
  C C6H12
  D C10H22

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2a1 mark

Crude oil is a mixture of hydrocarbons.

It can be separated into fractions.

Which of these mixtures shows formulae of substances that could be in the gaseous fraction of crude oil?

  A C2H4, C3H8, C4H10O
  B C2H4, C3H7Br, C4H10
  C C2H6, C3H8, C4H10
  D C2H6, C3H7Br, C4H10O

2b
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2 marks
Figure 11 shows the percentages of the fractions in crude oil from three different oil wells.

   percentage of fraction in crude oil from
fraction oil well A oil well B oil well C
gases 1 6 9
petrol 2 15 24
kerosene 6 14 20
diesel oil 7 10 16
fuel oil 26 28 30
bitumen 58 27 1

Figure 11

i)
State which oil well produces a crude oil containing the highest percentage of the high boiling point fractions.

(1)

ii)
A barrel of crude oil from oil well B weighs 130 kg.
Calculate the mass of kerosene in this barrel.

(1)

2c6 marks

Diesel is the fuel used in most bus engines.

Research is being carried out into the use of hydrogen, instead of diesel, as a fuel for buses.

Discuss the advantages and disadvantages of using hydrogen, rather than diesel, as a fuel for buses.

2d
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6 marks

Fractions of crude oil contain alkanes.

A sample of decane, C10H22, was cracked using the apparatus in Figure 12.

This produced a mixture of products, including ethene.

fig-12-q8d-1cho-2f-specimen-2018
Figure 4

i)
Explain how ethene is produced using the apparatus in Figure 4.

(3)

ii)

One molecule of decane produced two molecules of propene, C3H6, and one molecule of product Z.

C10H22 → 2C3H6 + product Z

What is the formula of product Z?

(1)

  A C4H8
  B C4H10
  C C7H14
  D C7H16

iii)

When decane undergoes complete combustion, a mixture of carbon dioxide and water is formed.

Complete the balanced equation for this reaction.

(2)

2C10H22 + .......... O2 → .......... CO2+ .......... H2O

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31 mark

Pollutants released from burning fuels can negatively affect health and the environment.

Which of the following is not the correct effect for the given pollutant?

 
      Pollutant  Effect
  A carbon dioxide global warming
  B sulfur dioxide acid rain
  C oxides of nitrogen respiratory problems
  D carbon particulates poisonous

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4a1 mark

Crude oil is found in the Earth’s crust.

Which of the statements about crude oil is correct?

  A crude oil is a finite resource
  B crude oil is a mixture of the elements hydrogen and carbon
  C all of the molecules in crude oil contain rings of carbon atoms
  D crude oil is used in cars as a fuel
4b1 mark

The substances ethane, C2H6, octane, C8H18, and pentadecane, C15H32, are all found in crude oil.

These substances

  A are used in cars as a fuel
  B have the same boiling point
  C are in the same homologous series
  D form different products when completely combusted in air
4c3 marks
i)
Use a word from the box to complete each of the sentences about the fractional distillation of crude oil.

condensed            heated           melted         solidified        stirred

Each word may be used once, more than once, or not at all.

(2)

The separation of crude oil into fractions occurs in a fractional distillation column.
Before crude oil is passed into the column it is ................................................. .

During the distillation, vapour rises up the column until it is cold enough for the
vapour to form a liquid. The vapour has been ................................................... .

ii)
Complete this sentence by underlining the correct answer in the box.

(1)

Compared with the fraction from the top of the column,

the fraction from the bottom of the column

has more carbon atoms per molecule.

has a lower viscosity.

is easier to ignite.

4d1 mark

When crude oil is separated into fractions, the amount of each fraction obtained rarely matches the demand for that fraction.

Figure 7 shows the relative amounts of four of the fractions obtained from a crude oil and the relative demand for each of these fractions.

fraction

relative amount obtained

from the crude oil

relative demand
gases 5 5
petrol 10 25
kerosene 20 25
fuel oil 45 5

Figure 7

State the fraction for which the relative amount obtained exceeds the relative demand.

4e3 marks

In January 2015 the United Kingdom produced 850 000 barrels of crude oil per day.
45% of this crude oil was fuel oil.

Calculate the number of barrels of fuel oil present in the 850 000 barrels of crude oil.

Give your answer to two significant figures.

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51 mark

Incomplete combustion occurs when there is insufficient oxygen for a reaction.

Which are the two main substances formed during incomplete combustion, aside from water?

 
  A Carbon monoxide and soot
  B Soot and sulfur dioxide 
  C Carbon dioxide and carbon monoxide 
  D Oxides of nitrogen and sulfur dioxide 

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6a1 mark

Crude oil is a complex mixture of substances.

Crude oil can be separated into useful fractions by fractional distillation.

Figure 7 shows a fractional distillation column and the fractions produced when a sample of crude oil is distilled.

fig-7-q6-1cho-2h-paper-1-june-2018

Figure 7

The properties of these fractions vary from the top of the column to the bottom of the column.

Which of the following is a trend in a property of the fractions obtained from the top of the column to those obtained from the bottom?

  A the average number of carbon atoms in molecules present decreases
  B the ease of ignition increases
  C the boiling points decrease
  D the viscosities increase
6b3 marks

Most of the substances in crude oil are alkanes.

i)
Which of the following is the general formula of an alkane?
(1)
  A CnH2n
  B CnH2n+1
  C CnH2n-1
  D CnH2n+2

ii)
Explain why alkanes are described as hydrocarbons.
(2)
6c2 marks

Figure 8 shows a graph of the boiling points of some alkanes against the number of carbon atoms in one molecule of each alkane.

fig-8-q6c-1cho-2h-paper-1-june-2018
Figure 8

Explain the pattern shown by this graph.

6d5 marks

When crude oil is separated into fractions, the amount of each fraction obtained rarely matches the demand for that fraction.

Figure 9 shows the relative amounts of six of the fractions present in a crude oil and the relative demand for each of these fractions.

fig-9-q6d-1cho-2h-paper-1-june-2018

Figure 9

Cracking is used to match the relative amount of a fraction of crude oil to the demand for that fraction.

i)
Use the information in Figure 9 to give the name of the fraction that is most likely to need to be cracked.
(1)
ii)
In a cracking reaction, reactants are heated to form products.
This reaction is endothermic.

On the axes provided, draw the reaction profile of this reaction.
Label the energy of the reactants, the energy of the products and the activation energy of the reaction.
(3)

fig-q6dii-1cho-2h-paper-1-june-2018

iii)
Dodecane, C12H26, can be cracked to form useful products.
Complete the equation for the cracking of dodecane by filling in the formula of the single molecule needed to balance the equation.

(1)

C12H26 rightwards arrow ....................................... + 3C2H4

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71 mark

Fractional distillation is the process by which crude oil is separated into simpler, more useful fractions.

Which of the following statements about the process of fractional distillation is correct?

  A The fractionating column is cooler at the bottom than at the top
  B The fractions collected at the top of the fractionating column have a high boiling point
  C The molecules in each fraction have a similar boiling point and carbon chain length
  D The fractions collected at the bottom of the fractionating column have a low viscosity

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8a1 mark

Most of the fuels used today are obtained from crude oil.

Which statement about crude oil is correct?

  A crude oil is a compound of different hydrocarbons
  B crude oil is a mixture of hydrocarbons 
  C crude oil contains different hydrocarbons, all with the same molecular formula 
  D crude oil is an unlimited supply of hydrocarbons 

8b3 marks

Crude oil is separated into several fractions by fractional distillation.

Two of these fractions are kerosene and diesel oil.

 
i)
State a use for each of these fractions.
 
(2)
 
kerosene ....................................................................................................
 
diesel oil ....................................................................................................
 
ii)
Figure 13 shows where the fractions kerosene and diesel oil are produced in the fractionating column.
 
fig-13-q8bii-1cho-2f-paper-1-june-2019
 
Figure 13
 
Kerosene is obtained higher up the column than diesel oil.
Kerosene and diesel oil fractions have slightly different properties.
 
Choose a property.
State how this property for kerosene compares with the property for diesel oil.
 
(1)
 
property ....................................................................................................
 
comparison ....................................................................................................
8c
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7 marks

Figure 14 shows the formulae of a molecule of butane and of a molecule of pentane.

Butane and pentane are neighbouring members of the same homologous series.

 
fig-14-q8c-1cho-2f-paper-1-june-2019
 
Figure 14
 
i)
Explain, using these formulae, why butane and pentane are neighbouring members of the same homologous series.
 
(2)
 
ii)
Butane has the formula C4H10.
 
Calculate the mass of carbon in 100 g of butane.
 
Give your answer to three significant figures.
 
(relative atomic masses: H = 1.00, C = 12.0;
relative formula mass: C4H10 = 58.0)
 
You must show your working.
 
(3)
 
iii)
Butane burns completely in air to form carbon dioxide and water.
 
Write the word equation for this reaction.
 
(2)

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91 mark

Kerosene, bitumen and diesel oil are fractions obtained through the fractional distillation of crude oil.

Which of the following shows the correct use of each fraction? 

      kerosene bitumen fuel oil
  A fuel for aircraft surfacing roads in power stations
  B fuel for trains in power stations fuel for aircraft
  C in domestic heating surfacing roads in power stations
  D fuel for aircraft in domestic cooking in domestic cooking

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10a3 marks

Methane is a hydrocarbon fuel.

i)
Complete the word equation for the complete combustion of methane in oxygen.
(2)

methane + ................................. → water + ................................

ii)
The incomplete combustion of methane can produce carbon and carbon monoxide.

Give the reason why carbon and carbon monoxide are produced in the incomplete combustion of methane.
(1)
10b2 marks

Crude oil is a complex mixture of hydrocarbons.
Crude oil can be separated into useful fractions by fractional distillation.

Figure 10 shows a fractional distillation column and the fractions produced when crude oil is distilled.

fig-10-q6b-1cho-2f-paper-1-nov-2020
Figure 10

i)
Name the fraction in Figure 10 that is used to surface roads.
(1)
ii)
Name the fraction in Figure 10 that contains hydrocarbons with the lowest boiling point.
(1)
10c1 mark

When crude oil is fractionally distilled, the demand for some fractions is more than the amount produced.

Figure 11 shows the relative amounts of each fraction in a crude oil and the relative demand for each of these fractions.

fraction relative amount relative demand
gases 2 6
petrol 12 29
kerosene 16 11
diesel oil 24 29
fuel oil 37 21
bitumen 9 4

Figure 11

Which of the following shows the fractions where the relative demand is greater than the relative amount in the crude oil?

  A kerosene, diesel oil, bitumen
  B gases, petrol, diesel oil 
  C gases, petrol, kerosene 
  D petrol, diesel oil, fuel oil
10d
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3 marks

Cracking involves the breaking down of large hydrocarbon molecules into smaller hydrocarbon molecules.

i)
Octane, C8 H18, can be cracked to produce one molecule of ethene, C2H4, and one molecule of CxH 14.

C8H18 → C2H4+ CxH14

Determine the value of x in the molecule of CxH14.
(1)

x = .........................................

ii)
Dodecane is a large hydrocarbon molecule.
When one molecule of dodecane is cracked the products are one molecule of octane and one molecule of butene.
dodecane → octane + butene

Calculate the maximum mass of octane that could be produced when 340 g of dodecane is cracked in this reaction.
(relative formula masses: dodecane = 170, octane = 114)
(2)
mass of octane = ............................................... g

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