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AQA Chemistry unit 1 > C1.4 Crude Oil and Fuels > Flashcards

C1.4 Crude Oil and Fuels Flashcards

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1
Q

What is a mixture?

A

A substance made from two or more elements or compounds that aren’t chemically bonded to each other.

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2
Q

What is a hydrocarbon?

A

A hydrocarbon is a molecule that only contains hydrogen and carbon.

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3
Q

Name the process used to separate crude oil into fractions.

A

Fractional distillation.

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4
Q

Where do compounds with a small number of carbon atoms leave the fractionating column.

A

Near the top.

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5
Q 
Butane - 4 Carbon atoms
Decane - 10 Carbon atoms
Icosane - 20 Carbon atoms
Tetracontane - 40 Carbon atoms
Which of the hydrocarbons will condense at the lowest temperature?
A

Butane

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6
Q 
Butane - 4 Carbon atoms
Decane - 10 Carbon atoms
Icosane - 20 Carbon atoms
Tetracontane - 40 Carbon atoms
Which of the hydrocarbons will condense nearest the bottom of the fractionating column?
A

Tetracontane

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7
Q

Fraction: Approximate boiling temp range (‘C)
Petrol: 30 - 80
Naphtha: 80 - 190
Kerosene: 190 - 250
Diesel: 250 - 350
Which of the fractions in the table will be removed closest to the top of the fractionating column?

A

Petrol

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8
Q

Fraction: Approximate boiling temp range (‘C)
Petrol: 30 - 80
Naphtha: 80 - 190
Kerosene: 190 - 250
Diesel: 250 - 350
Octane has a boiling point of 125’C.
In which of the fractions will octane be found?

A

Naphtha

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9
Q

Octane has a boiling point of 125’C.

At what temperature will octane condense?

A

125’C

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10
Q

Name the alkane that has the chemical formula C3H8.

A

Propane

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11
Q

Why are alkanes described as being “saturated”?

A

Because alkanes only contain single carbon-carbon bonds.

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12
Q

Describe the trend in flammability of the alkanes.

A

The shorter the carbon chain, the more flammable the alkane is. The longer the carbon chain, the less flammable the alkane is.

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13
Q

Octane has eight carbon atoms in it. What is its chemical formula?

A

C8H18

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14
Q

Hexadecane is an alkane with long carbon chains. Explain why hexadecane is a suitable alkane to use in lubricating oil.

A

Hexadecane is viscous which makes it suitable for use as a lubricant.

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15
Q

What two products are formed when a hydrocarbon fuel is completely combusted?

A

Carbon dioxide and water (vapour).

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16
Q

What other products may be released if a hydrocarbon fuel undergoes partial combustion?

A

Carbon monoxide, carbon particulates, unburnt fuel.

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17
Q

What gas other than carbon dioxide and water vapour will be formed if a fuel containing sulfur impurities is burnt in air?

A

Sulfur dioxide

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18
Q

Under what conditions will nitrogen oxides form when a hydrocarbon fuel is burned?

A

When the fuel burns at a really high temperature.

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19
Q

Name two gases that can cause acid rain.

A

Sulfur dioxide and oxides of nitrogen.

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20
Q

Give three ways in which acid rain can damage the environment.

A

It can cause lakes to become acidic and many plants and animals may die as a result.
It can kill trees.
It can damage limestone buildings or statues

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21
Q

Suggest three ways of reducing acid rain.

A

The sulfur impurities could be removed from the fuel before it is burnt.
Harmful gases could be removed from fumes before they are released into the atmosphere.
The use of fossil fuels could be reduced.

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22
Q

What is global warming?

A

Global warming is the increase in the average temperature of the earth.

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23
Q

Suggest one consequence of global warming.

A

It could cause other types of climate change such as changing rainfall patterns.
It could cause severe flooding due to melting of the polar ice caps.

24
Q

Hexadecane (C16H34) can be used as a fuel. When it undergoes complete combustion carbon dioxide and water vapour are released.
Will using hexadecane as a fuel contribute to climate change? Explain your answer.

A

Yes, because one of the products is carbon dioxide which which causes global warming.

25
Q

Hexadecane (C16H34) can be used as a fuel. When it undergoes complete combustion carbon dioxide and water vapour are released.
Could burning hexadecane result in acid rain? Explain your answer.

A

Yes, if the hexadecane contains sulfur impurities, sulfur dioxide may be produced which could cause acid rain.
If the hexadecane is burnt at high temperatures, nitrogen oxides could be produced which could cause acid rain.

26
Q

A study by scientists at a local weather station has shown that over the last 50 years, the amount of sunlight reaching the weather station has decreased. Suggest a possible explanation for this finding.

A

Global dimming - it could be caused by particles of soot and ash that are released into the atmosphere when fossil fuels are burnt. These particles could reflect sunlight back into space or could help produce more clouds that reflect the sunlight back into space.

27
Q

What is the structure of methane?

A 
H
       |
H - C - H
       |
      H
28
Q

What is the general formula of alkanes

A

CnH2n+2

29
Q

What is the boiling point, viscosity and flammability of a short hydrocarbon like compared to a longer one?

A

A short hydrocarbon has a lower boiling point, is less viscous and more flammable than a longer hydrocarbon.

30
Q

What is the boiling point, viscosity and flammability of a long hydrocarbon like compared to a shorter one?

A

A long hydrocarbon has a higher boiling point, is more viscous and less flammable than a shorter hydrocarbon.

31
Q

Write a balanced symbol equation for the complete combustion of pentane (C5H12).

A

C5H12 + 802 -> 5CO2 + 6H2O

32
Q

Some hexane (C6H14) burns incompletely producing carbon monoxide and water as the only products. Write a balanced symbol equation for this combustion.

A

2C6H14 + 13O2 -> 12CO + 14H2O

33
Q

What is a biofuel?

A

A renewable fuel made from plant material.

34
Q

Give two examples of biofuels.

A

Ethanol and biodiesel.

35
Q

Give three advantages and two disadvantages of using ethanol as a fuel.

A

Ethanol is carbon neutral because the CO2 released from the plant when burned was taken in from the plant during its lifetime. It is also renewable as it is made from sugar cane which can continuously be grown. Growing crops for ethanol provides jobs.
Engines need to be converted before they can use ethanol fuels. If demand for ethanol increases, farmers may switch to growing crops for ethanol instead of crops for food and food prices could increase.

36
Q

What is biodiesel made from?

A

Vegetable oils e.g. rapeseed oil and soy bean oil.

37
Q

A distribution company wants to reduce its impact on the environment. Its fleet of distribution vans currently runs on diesel fuel. Suggest a way that this company could be more environmentally friendly without having to replace all of the vans it already has.

A

The company could use biodiesel to run their vans rather than diesel.

38
Q

A company makes hydrogen gas from the electrolysis of water. The electricity needed for this process comes from a fossil fuel power station. The company claims their hydrogen is a completely clean fuel because the only product formed when hydrogen burns is water.
Explain why this claim is incorrect.

A

The energy to make the hydrogen comes from burning fossil fuels which releases carbon dioxide and other pollutants.

39
Q

A company makes hydrogen gas from the electrolysis of water. The electricity needed for this process comes from a fossil fuel power station. The company claims their hydrogen is a completely clean fuel because the only product formed when hydrogen burns is water.
What could the company do to make its hydrogen a completely clean fuel?

A

They could use electricity from a from a renewable energy source to make their hydrogen.

40
Q

Describe the process of fractional distillation. (4 marks)

A

The crude oil is heated so that it evaporates (1 mark)
The vaporised gases rise up the fractionating column and cool gradually (1 mark)
As they cool they condense (1 mark)
Different compounds condense at different temperatures and so they are separated (1 mark)

41
Q

Petrol is removed from near the top of the fractionating column. What does this tell you about the hydrocarbons that make up petrol?

A

They have short carbon chains.

42
Q

Outline the environmental impacts of using petrol as a fuel. (6 marks)

A

Burning petrol releases carbon dioxide which contributes to global warming.
If the petrol has sulfur impurities in it, sulfur dioxide might form when the petrol burns which contributes to global warming.
If the fuel is burnt at very high temperatures, oxides of nitrogen may be formed and this contributes to acid rain.
If there is not enough oxygen available when the fuel is burnt carbon particulates may be produced and released into the atmosphere. These contribute to global dimming.

43
Q

Give two reasons why an alternative to fossil fuels is needed.

A

Fossil fuels are non-renewable so they will eventually run out.
Burning fossil fuels contributes to global warming and global dimming and can lead to the production of acid rain.

44
Q

Explain why ethanol is a ‘carbon neutral’ fuel.

A

Because the CO2 released when ethanol is burnt was taken up by the plants as they grew.

45
Q

Suggest three reasons why most people have not switched to using ethanol powered cars.

A

Engines need to be converted before they will work with ethanol fuels.
Ethanol is not widely available.
People have concerns that using ethanol as a fuel may lead to increased food prices.

46
Q

Biodiesel produces much less sulfur dioxide when it is burned than normal diesel does. Explain why this is an advantage. (2 marks)

A

Sulfur dioxide can cause acid rain (1 mark) so a fuel that produces less sulfur dioxide will be better for the environment (1 mark)

47
Q

Discuss one positive and one negative social impact of producing and using biodiesel. (4 marks)

A

Growing crops for biodiesel is labour intensive (1 mark) so provides jobs for local people (1 mark)
If there is increased demand for biodiesel, farmers may switch to growing crops for biodiesel and fewer crops will be grown for food (1 mark) so food will become more expensive (1 mark)

48
Q

Which alkane out of propane, heptane and decane is likely to be the least flammable? Explain your answer.

A

Decane because it has the longest carbon chains.

49
Q

Which alkane out of propane, heptane and decane would be most suitable to use in bottled gas? Explain your answer. (2 marks)

A

Propane because it has the shortest carbon chains (1 mark) so it has the lowest boiling point. (1 mark)

50
Q

Write a balanced symbol equation for the complete combustion of heptane.

A

C7H16 + 11O2 -> 7CO2 + 8H2O

51
Q

Under what conditions would carbon monoxide form when heptane is burned?

A

If there is not enough oxygen.

52
Q

Describe how oxides of nitrogen could be formed when heptane is burned. (2 marks)

A

If the heptane is burned at a very high temperature (1 mark) nitrogen in the air will react with oxygen in the air to form nitrogen oxides (1 mark)

53
Q

A town council wants to be more environmentally friendly and is planning to swap its diesel powered buses for a fleet of buses that are powered by hydrogen gas.
Why is using hydrogen more environmentally friendly than using diesel? (1 mark)

A

Because the only product when hydrogen is burned is water.

54
Q

A town council wants to be more environmentally friendly and is planning to swap its diesel powered buses for a fleet of buses that are powered by hydrogen gas.
Suggest four concerns that the town’s residents might have.

A

It’s expensive to replace all of the town’s buses.
Hydrogen is highly flammable so could cause explosions.
Hydrogen is difficult to store.
You still need to use energy from other sources to make the hydrogen.

55
Q

A town council wants to be more environmentally friendly and is planning to swap its diesel powered buses for a fleet of buses that are powered by hydrogen gas.
Suggest a cheaper option the town hall could use for making its buses more environmentally friendly. Explain your answer. (4 marks)

A

The town hall could use biodiesel (1 mark) because it doesn’t require engines to be converted so it would be cheaper than hydrogen gas (1 mark).
Biodiesel is also carbon neutral (1 mark) and is a renewable resource so it is better for the environment (1 mark).

AQA Chemistry unit 1 (7 decks)

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