Organic Chemistry (OCR GCSE Combined Science A (Gateway): Chemistry): Exam Questions

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     

[1]

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

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]

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.

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.

[3]

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.