Organic Chemistry (OCR Gateway GCSE Chemistry)

Exam Questions

1a3 marks

This question is about hydrocarbons.

The table shows some information about alkanes.

Name of alkane Molecular formula Structure
Methane CH4 q171-paper-2-june-2019-ocr-gcse-chem
Ethane ................................ q172-paper-2-june-2019-ocr-gcse-chem
................................ C4H10 ................................

Complete the table.

1b2 marks

Ethane is a saturated hydrocarbon.

Explain why ethane is called both a hydrocarbon and saturated.

1c2 marks

A student has two test tubes. One contains ethane and one contains ethene.

q17c-paper-2-june-2019-ocr-gcse-chem

The student added bromine water to each test tube.

Describe what she observes.

Ethane ........................................

Ethene ........................................

1d1 mark

Ethane belongs to the homologous series called the alkanes.

What is the name of the homologous series that ethene belongs to?

1e2 marks

Pentane, C5H12, is an alkane found in petrol.

Pentane undergoes complete combustion in excess oxygen, O2.

Carbon dioxide and water are made.

Write the balanced symbol equation for the complete combustion of pentane.

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2a4 marks

Crude oil is used as a source of fuels. It is separated into many fractions by fractional distillation.

The diagram shows a fractionating column.

q18-paper-2-specimen-2016-ocr-gcse-chem

Crude oil contains a mixture of hydrocarbons that boil at different temperatures.


Describe how crude oil can be separated using a fractionating column.

2b1 mark

The alkane, C15H32, is cracked to make an alkene, C6H12 and an alkane, C3H8.

Construct the balanced symbol equation for this reaction.

2c1 mark

Alkenes are used to make polymers. Polymers are used to make clothes such as socks and jumpers.

Suggest one property of a polymer that makes it suitable for making clothes.

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3a2 marks

Fractional distillation separates crude oil into useful fractions.

Look at the table.

It shows the percentage of each fraction made from crude oil. It also shows the percentage of each fraction needed for everyday uses.

Fraction Percentage made by
fractional distillation
Percentage needed for
everyday uses
Gases 4 11
Petrol 11 22
Naphtha 10 18
Paraffin 12 20
Fuel oil 22 10
Waxes and tar 23 4

i)

Which fraction is made in the greatest percentage?

Tick (✓) one box

Gases square
Petrol square
Naphtha square
Paraffin square
Fuel oil square
Waxes and tar square

ii)
Which fraction is needed in the smallest percentage?

Tick (✓) one box.

Gases square
Petrol square
Naphtha square
Paraffin square
Fuel oil square
Waxes and tar square
3b3 marks

Cracking changes large hydrocarbon molecules into smaller hydrocarbon molecules.

i)
One of the conditions needed for cracking is a high pressure.

Write down one other condition needed.

[1]

ii)
Cracking is a very useful reaction.

Explain why.

Use information from the table in your answer

[2]

3c
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3 marks

In 2008 the USA produced 4 900 000 barrels of crude oil per day. In 2019 this had increased to 11 000 000 barrels of crude oil per day.

Calculate the percentage increase in the number of barrels of crude oil produced per day from 2008 to 2019.

Use the formula: percentage increase =  increase over original× 100

Give your answer to 2 decimal places.

Percentage increase = ..................................................... % 

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4a1 mark

Crude oil is separated into useful fractions using fractional distillation.

The table shows the percentages of crude oil fractions from different oil wells.

Fraction Percentage of fraction in crude oil
Oil well X Oil well Y Oil well Z
LPG 2 7 10
Petrol 3 10 25
Paraffin 6 15 20
Diesel 7 11 15
Fuel oil 26 29 28
Bitumen 56 28 2

Which oil well contains the highest percentage of low boiling point fractions?

Tick (✓) one box.

X     square

Y     square

Z     square

4b
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2 marks

A barrel of crude oil from oil well Y has a mass of 139 kg.

Calculate the mass of fuel oil in this barrel.

Mass = ..................................................... kg

4c1 mark

Fractions from crude oil contain alkanes.

Alkanes have the general formula CnH2n+2.

Write the formula of hexadecane, the alkane with 16 carbon atoms.

4d3 marks

A sample of decane was cracked.

Look at the diagram of the apparatus used.

q20d-paper-2-june-2019-ocr-gcse-chem

i)
Describe how this apparatus is used to produce ethene from decane.
[2]
ii)
One molecule of decane, C10H22, produced two molecules of ethene, C2H4, and one molecule of product Z.

C10H22rightwards arrow 2C2H4 + product Z

Write the formula for product Z.
[1]

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5a2 marks

This question is about compounds of carbon.

Look at the displayed formulae of ethane, propane and ethene.

q22-paper-2-nov-2020-ocr-gcse-chem

Ethane and propane are both members of the homologous series called the alkanes.

Write down two reasons why ethane and propane are members of the same homologous series.

5b3 marks

Many ethene molecules react together to form the polymer poly(ethene).

This reaction is called polymerisation.

i)
Why do ethene molecules undergo polymerisation but ethane molecules do not?

 [1]

ii)
Complete the diagram to show the displayed formula of poly(ethene).
q22bii-paper-2-nov-2020-ocr-gcse-chem

[2]

5c6 marks

Propane gas is used as a fuel for cooking and heating in caravans.

q22c-paper-2-nov-2020-ocr-gcse-chem

Incomplete combustion of propane can occur if the campers do not take sensible precautions.

Describe how incomplete combustion of hydrocarbons such as propane happens and the problems it can cause for campers.

Include a balanced symbol equation in your answer.

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6a3 marks

This question is about life-cycle assessment.

A car company is developing three new cars:

  • A petrol car
  • A diesel car
  • An electric car.

They do a life-cycle assessment of each car.

Look at the information about the life-cycle assessment of each car.

q24a-paper-2-june-2018-ocr-gcse-chem

The company decides to manufacture and sell the electric car.

Explain why they make this choice.

Use the information from the life-cycle assessment to help you.

6b3 marks

The fuels for the petrol and diesel cars are made from crude oil.

Crude oil is separated into different parts by fractional distillation.

The diagram shows a fractionating column.

q24b-paper-2-june-2018-ocr-gcse-chem

Explain why crude oil vapour can be separated by fractional distillation.

6c2 marks

The table shows the boiling points of molecules present in different crude oil fractions.

Molecule Boiling point (°C)
A −2
B 125
C 216
D 502

Which molecule, A, B, C or D, is in the LPG fraction?

Explain your decision.

6d3 marks

Car manufacturers are developing cars that are powered by hydrogen/oxygen fuel cells.

The table shows some information about a 200 km journey using an electric car and a car using a fuel cell.

Feature Electric Fuel cell
Refuelling time (minutes) 360 4
Cost of refuelling (£) 3.20 4.20
CO2 emitted (kg) 48 36
Mass of car (kg) 1550 1200

Evaluate the advantages and disadvantages of using a car powered by a fuel cell, rather than an electric car for the 200 km journey.

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7a1 mark

A student is using the internet to find out about alcohols. The student finds the following information.

Name Number of carbon atoms Boiling point
(°C)
Methanol 1 65
Ethanol 2 79
Propanol 3 97
Pentanol 5 138
Hexanol 6 156

Plot a graph of the boiling points of the alcohols on the grid. Draw a line of best fit.

q25a-paper-2-june-2018-ocr-gcse-chem

7b2 marks
i)
The student could not find a value for the boiling point of butanol, C4H9OH.

Use the graph to estimate the boiling point of butanol.

Answer = ..................................... °C

[1]

ii)
Draw the displayed formula of butanol, C4H9OH.

[1]

7c1 mark

The alcohols all react in a similar way because they all contain the same functional group.

What is the functional group in an alcohol molecule?

7d1 mark

Ethanol, C2H5OH, can be oxidised to ethanoic acid using potassium manganate(VII).

What is the formula of ethanoic acid?

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8a2 marks

Poly(propenenitrile) is an addition polymer.

Look at the flow chart. It shows how poly(propenenitrile) is made from crude oil.

q20-paper-4-specimen-2016-ocr-gcse-chem

Crude oil is a mixture of hydrocarbons.

Fractional distillation separates the hydrocarbons in this mixture.

Explain how fractional distillation separates the hydrocarbons, in terms of intermolecular forces.

8b1 mark

Look at the displayed formula for propenenitrile.

q20b-paper-4-specimen-2016-ocr-gcse-chem

How can you tell from the displayed formula that propenenitrile is an unsaturated compound?

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9a1 mark

Look at the displayed formula of the monomer butene.

q22-paper-4-june-2018-ocr-gcse-chem

What feature of butene molecules allows them to act as monomers?

9b1 mark

Butene is an alkene.

What is the general formula for an alkene?

9c2 marks

Butene undergoes addition polymerisation to form poly(butene).

Write the displayed formulae, for poly(butene).

9d1 mark

DNA molecules are polymers made from four different monomers.

What are the monomers in DNA called?

9e4 marks

Higher Only

Polyesters are polymers made by condensation polymerisation.

i)
What is the minimum number of functional groups that a monomer must have to form a condensation polymer?

[1]

ii)

Polyesters are made from a carboxylic acid and an alcohol.

Complete the block diagram to show the formation of a polyester.

q22eii-paper-4-june-2018-ocr-gcse-chem

[2]

iii)
What is the formula of the molecule that is eliminated in the reaction to form a polyester?

[1]

9f6 marks

Higher Only

Nylon is another polymer formed in a condensation polymerisation reaction.

Nylon can be made from hexanedioyl dichloride and hexane‑1,6‑diamine.

Both chemicals are highly corrosive.

A solvent is needed which is highly flammable.

i)
Describe how to make nylon in a laboratory.

[3]

ii)
Describe and explain three precautions needed to control the hazards in this experiment.

[3]

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10a3 marks

Look at the displayed formulae of some compounds.

q20-paper-4-nov-2020-ocr-gcse-chem

i)
Which two compounds are members of the same homologous series?

................................. and .................................

ii)
Write down two reasons for your answer in (a)(i).

10b3 marks

Higher Only

Many molecules of compound C react together to form a polymer.

This reaction is called addition polymerisation.

i)
Draw the displayed formula of the polymer formed by compound C.

[2]

ii)

Another type of polymerisation is condensation polymerisation.

Describe one difference between addition polymerisation and condensation polymerisation.

[1]

10c6 marks

A student has unlabelled samples of three liquids.

The student knows that the three liquids are:

  • pentane, C5H12
  • pentene, C5H10
  • ethanoic acid, CH3COOH.

Describe tests that the student should do to identify each of the three liquids.

Include balanced symbol equations for the reactions described.

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1a2 marks

A student did an experiment to prove that methane gas, CH4, produces carbon dioxide and water when it burns.

Look at the diagram of her experiment.

q21-paper-4-june-2019-ocr-gcse-chem

The limewater turned milky showing that carbon dioxide had been formed.

A small amount of a colourless liquid condensed in boiling tube X. The student said that this proved that burning methane produced water.

The teacher said that the experiment had been set up incorrectly.

The teacher said that the student’s conclusion about water was not valid.

Describe and explain how the student could change how the experiment is set up to prove that water is produced by burning methane.

1b4 marks

Higher Only

Look at the monomers shown in the table.

fig-21b-paper-4-june-2019-ocr-gcse-chem

Two of the monomers from the table react to form a polymer which is a polyester.

Explain, using the appropriate monomers from the table, how the polyester is formed.

Include the type of polymerisation and an equation for the reaction in your answer.

1c2 marks

DNA and proteins are biological polymers.

i)
How many different monomers are found in a DNA polymer?
[1]
ii)
What are the monomers in proteins called?
[1]
1d3 marks

An alcohol, X, has the formula C3H7OH.

Alcohol X can be oxidised to a compound, Y, with the molecular formula C3H6O2.

i)
Compound Y is not an alcohol but is a member of another homologous series.

Write down the name of this homologous series.

[1]

ii)
Draw the displayed formula of a molecule of alcohol X and of a molecule of compound Y.

Show all the covalent bonds.

Alcohol X

Compound Y
[2]

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