Fuels (Edexcel GCSE Chemistry)

Which molecule can be cracked to produce hexane, C₆H₁₄? 

Crude oil is a mixture of hydrocarbons.

It can be separated into fractions.

Figure 11

(1)

(1)

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.

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.

(3)

(2)

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

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?

Crude oil is found in the Earth’s crust.

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

These substances

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 ................................................... .

(1)

Compared with the fraction from the top of the column,

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.

Figure 7

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

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.

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

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

Crude oil is a complex mixture of substances.

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?

Most of the substances in crude oil are alkanes.

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

Explain the pattern shown by this graph.

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.

Figure 9

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

(1)

C₁₂H₂₆  ....................................... + 3C₂H₄

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?

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

Crude oil is separated into several fractions by fractional distillation.

Two of these fractions are kerosene and diesel oil.

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.

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? 

Methane is a hydrocarbon fuel.

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

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.

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.

Figure 11

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

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

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

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

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.

Higher Only

The energies of some bonds are shown in Figure 2.

bond	bond energy in kJmol-1
	435
	496
	805
	463

Figure 2

Methane burns in oxygen to form carbon dioxide and water.

The equation shows the structures of the molecules.

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

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

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.

Figure 3

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

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

(2)

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 ..................................

Higher Only

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

Figure 1

Figure 12 shows some bond energies.

bond	bond energy in kJ mol-1
	347
	358
	413
	464
	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

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

Figure 3

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

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

Figure 1 shows some of these processes and reactions. 

Figure 1

Describe how crude oil is separated into fractions.

Name the reaction that occurs in reactor 2. 

Compare the properties of gasoline and fuel oil.

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.

Oxides of nitrogen also impact the environment.

Explain how oxides of nitrogen are formed in car exhausts. 

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

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. 

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.

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.