Organic Chemistry (OCR GCSE Chemistry A (Gateway))

Crude oil is used as a source of fuels. It is separated into many fractions by fractional distillation. The diagram shows a fractionating column.

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

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

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

Construct the balanced symbol equation for this reaction.

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.

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.

i) Which fraction is made in the greatest percentage?

Tick (✓) one box

ii) Which fraction is needed in the smallest percentage?

Tick (✓) one box.

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]

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 =  × 100

Give your answer to 2 decimal places.

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

Crude oil is separated into useful fractions using fractional distillation.

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

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

Tick (✓) one box.

X     

Y     

Z     

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

Fractions from crude oil contain alkanes.

Alkanes have the general formula C_nH_2n+2.

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

A sample of decane was cracked.

Look at the diagram of the apparatus used.

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.

C₁₀H₂₂ 2C₂H₄ + product Z

Write the formula for product Z.

[1]

This question is about compounds of carbon.

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

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.

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).

[2]

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

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.

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.

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.

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.

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

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

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

Explain your decision.

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.

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

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

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

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]

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?

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

What is the formula of ethanoic acid?

Poly(propenenitrile) is an addition polymer.

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

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.

Look at the displayed formula for propenenitrile.

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

Look at the displayed formula of the monomer butene.

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

Butene is an alkene.

What is the general formula for an alkene?

Butene undergoes addition polymerisation to form poly(butene).

Write the displayed formulae, for poly(butene).

DNA molecules are polymers made from four different monomers.

What are the monomers in DNA called?

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.

[2]

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

[1]

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]

Look at the displayed formulae of some compounds.

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

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

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

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]

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.