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Chemistry > Fuels > Flashcards

Fuels Flashcards

1
Q

What are hydrocarbons?

A

Compounds that contain hydrogen and

carbon atoms only.

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2
Q

What is crude oil?

A
  • Acomplex mixture of hydrocarbons.
  • Contains molecules with rings or chains of carbon
    atoms.
  • An important source of useful substances like fuels
    and feedstocks for the petrochemical industry.
  • Afinite resource.
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3
Q

Where can crude oil be found?

A

Under the sea and ground.

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4
Q

What does it mean when crude oil is described as

‘finite’?

A

It will run out.

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5
Q

How can crude oil be separated?

A

Fractional distillation

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6
Q

How does the process of fractional distillation work

to separate crude oil?

A
  • Crude oil is vaporised before it enters a fractionating column.
  • The fractionating column is hotter at the bottom than at the
    top. The vapours rise up and condense at different fractions
    depending on their boiling points.
  • Hydrocarbons with low boiling points will be tapped off the
    top of the column and hydrocarbons with high boiling points
    will be tapped off the bottom of the column
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7
Q

Why is crude oil separated?

A

Unseparated crude oil isn’t very useful
but the separated products (such as
petrol) are very useful

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8
Q

Refinery gas is a fraction of crude oil. What are its

common uses?

A

Heating and cooking

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9
Q

Which fraction of crude oil is used as fuel in cars?

A

Petrol (gasoline).

Diesel is also less commonly used

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10
Q

Kerosene is a fraction of crude oil. What is a

common use of kerosene?

A

Aircraft fuel

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11
Q

Diesel oil is a fraction crude oil. What is it commonly

used for?

A

Fuel for some cars and trains.

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12
Q

Which fraction of crude oil is used for road surfacing

and roofs?

A

Bitumen

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13
Q

Fuel oil is a fraction of crude oil. What is it commonly

used for?

A

Fuel for large ships and in some power

stations.

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14
Q

How do the hydrocarbons at each faction differ?

A
  • Boiling points.
  • Ease of ignition.
  • Viscosity.
  • The number of hydrogen and carbon atoms their molecules have
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15
Q

Where in the fractionating column do hydrocarbons with the highest viscosity condense?

A

Viscosity is how thick and sticky a substance is.

The hydrocarbons with the highest viscosity
(like bitumen) are collected at the bottom of the
fractionating column.

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16
Q

What are the properties of hydrocarbons that are
tapped from the top of the fractionating column, like
petrol and refinery gas?

A
  • Low boiling point.
  • Highly volatile.
  • Easily ignited.
  • Shorter carbon chains (small molecules).
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17
Q

What is a homologous series?

A 
Series of compounds which:
- Have the same general formula.
- Have similar chemical properties.
- Differ by CH2
in molecular formula form
neighbouring molecules.
- Slight variation in physical properties.
18
Q

Products from crude oil mostly belong to which homologous series?

A

Alkane homologous series

19
Q

What are the only products when a hydrocarbon fuel

undergoes complete combustion?

A

Water (H2O) and carbon dioxide (CO2)

20
Q

True or false? Energy is given out when a fuel

undergoes complete combustion

A

TRUE

The reaction is exothermic

21
Q

Write a balanced symbol equation for the complete

combustion of ethane

A

2C2H6 + 7O2 → 4CO2 + 6H2O (check google if unsure)

22
Q

When does incomplete combustion occur? What is

required to ensure complete combustion occurs?

A

Incomplete combustion occurs when there is an insufficient supply of oxygen. To ensure complete combustion occurs, the reaction should be carried out with excess oxygen.

23
Q

What are the products of incomplete combustion?

A

Carbon particulates - soot (C).
Carbon monoxide (CO).
Water (H2O)

24
Q

Write a balanced symbol equation for the incomplete

combustion of methane to form carbon monoxide

A

2CH4 + 3O2 → 2CO + 4H2O (check google if unsure)

25
Q

Write a balanced symbol equation for the incomplete

combustion of methane to form carbon particulates

A

CH4 + O2 → C + 2H2O (check google if unsure)

26
Q

What are the problems with carbon monoxide?

A

Carbon monoxide is a toxic gas.

It is colourless and odourless and if breathed
in can cause death by preventing the red
blood cells from carrying oxygen around the
body.

27
Q

What are the problems with incomplete combustion?

A
  • Produces carbon monoxide which is toxic and
    can be fatal if breathed in.
  • Produces carbon particulates (soot) which
    cause global dimming and respiratory
    problems.
28
Q

Why is sulfur dioxide sometimes produced when

burning hydrocarbon fuels?

A

Some hydrocarbon fuels contain sulfur
impurities. When the fuel is burned, the
sulfur reacts with oxygen to form sulfur
dioxide.

29
Q

How is acid rain produced?

A

Sulfur dioxide (produced when combusting impure hydrocarbon fuels) evaporates into the air. It reacts with water in the clouds to form sulfuric acid. This is ‘acid rain’.

30
Q

What problems can acid rain cause?

A 
- Corrodes buildings and statues made of
limestone.
- Kills/damages the vegetation.
- Lowers the pH of large bodies of water,
killing the wildlife.
31
Q

How are oxides of nitrogen produced from car engines?

A

The high temperature and pressure of a car
engine causes nitrogen and oxygen from
the air to react together.

32
Q

What problems are associated with oxides of

nitrogen?

A
  • Pollutants.
  • Produce acid rain with similar effects
    as SO2.
  • Cause respiratory problems
33
Q

What are the advantages of using hydrogen as a fuel

in cars?

A
  • It releases more energy per kg compared to
    most other fuels.
  • Water is the only product so no pollutants.
  • Renewable source as hydrogen can be
    extracted from water.
34
Q

What are the disadvantages of using hydrogen as a

fuel in cars?

A
  • It is expensive to produce and a lot of energy
    is required for the electrolysis of water to
    acquire the hydrogen.
  • Difficult and dangerous to store hydrogen
    because it is very volatile and easily ignites.
35
Q

Name the non-renewable fossil fuel found in natural gas

36
Q

Are petrol, kerosene and diesel renewable fuels?

A

No, they are non-renewable.

They are finite resources which are not
being readily replaced.

37
Q

What is cracking?

A

Breaking down large hydrocarbons into smaller more useful ones.

Saturated alkanes are cracked into shorter chain alkanes and short chain unsaturated alkenes.

38
Q

What do the terms saturated and unsaturated mean?

A

Saturated - only contains single bonds

Unsaturated - contains some C=C
double bonds.

39
Q

What type of reaction is cracking?

A

Thermal decomposition

40
Q

Why is cracking necessary?

A

The demand for shorter chain alkenes
and alkanes is much greater than the
demand for long chain alkanes.

41
Q

Crude oil fraction orders?

A 
Refinery gas
Petrol
Kerosene
Diesel
Fuel oil
Bitumen

Chemistry (30 decks)

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