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Chemistry > 20 - Hydrocarbons from fossil fuels > Flashcards

20 - Hydrocarbons from fossil fuels Flashcards

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1
Q

What three types of fossil fuels are there?

A

Coal, petroleum and natural gas

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2
Q

How is coal formed? (3 points)

A

Coal is formed from the remains of plants that lived on Earth hundreds of millions of years ago. Due to movements of the Earth’s crust, the plant remains were buried under layers of mud and sand. High pressure, temperature, and bacterial action changed the plants into coal.

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3
Q

What is the colour and form (e.g. solid) of petroleum and what does it contain?

A

Petroleum, or crude oil/oil, is a thick, black, oily liquid consisting mainly of hydrocarbons.

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4
Q

What does natural gas contain and what is its main component?

A

Natural gas is a mixture of hydrocarbons consisting mainly of methane.

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5
Q

What is the relationship between petroleum and natural gas?

A

They are often found together.

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6
Q

How is petroleum/natural gas formed? (3 points)

A

They are formed from the remains of dead sea plants and animals from hundreds of millions of years ago. The remains of these organisms were covered by layers of mud and sand. High pressure, temperature, and bacterial action changed the animals and plants into petroleum and natural gas.

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7
Q

How is coal extracted?

A

It is extracted through mining.

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8
Q

How is petroleum extracted?

A

It is extracted through oil rigs. In an oil rig, a deep well is drilled through the earth and petroleum can be pumped up.

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9
Q

What are the two types of hydrocarbons obtained from crude oil?

A

Aromatic hydrocarbons and aliphatic hydrocarbons.

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10
Q

What are aliphatic hydrocarbons?

A

Aliphatic hydrocarbons are hydrocarbons joined in straight chains, branched chains, and non-aromatic rings.

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11
Q

What are aromatic hydrocarbons?

A

Aromatic hydrocarbons are compounds that contain the benzene ring.

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12
Q

What is benzene used for?

A

It is used as a starting material to manufacture chemicals such as styrene and polystyrene.

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13
Q

What is oil refining?

A

Oil refining is the process of separating hydrocarbons in petroleum to give useful products.

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14
Q

Explain the principle of fractional distillation of crude oil.

A

Hydrocarbons in petroleum have different molecular sizes. Hydrocarbons with different molecular sizes have different boiling points because Van der Waals’ forces are stronger between large molecules. Molecules with different boiling point ranges can be separated into fractions.

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15
Q

Where is oil refining done?

A

Oil refinery

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16
Q

Explain the initial procedures of oil refining. (3 points)

A
  1. Petroleum is heated to 400 degrees celsius.
  2. The hot oil is pumped to the bottom of a fractionating tower.
  3. The vapours rise up to the tower and cool. Different fractions condense at different points of the fractionating tower.
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17
Q

What is the purpose of bubble caps in a fractionating tower? Where are they found within the tower?

A

They make the separation of fractions more effective. They are found on each level of the tower.

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18
Q

Draw the setup for fractional distillation in the laboratory.

A

NA

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19
Q

Compare hydrocarbons with the following boiling point ranges: 100, 100-150, 150-200, 200-250 in the following areas:

i) Color
ii) Volatility
iii) Viscosity
iv) Flammability
v) Colour and sootiness of flame when burnt

A

i) Colorless, Very pale yellow, Yellow, Brown
ii) Evaporates quickly -> Evaporates slowly
iii) Non-viscous -> fairly viscous
iv) Easy to burn -> Hard to burn
v) Yellow with blue edges, non-sooty
yellow/orange, slightly sooty
orange, sooty
orange, very sooty

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20
Q

State two uses of petroleum fractions

A

1) As fuels

2) As a source of hydrocarbons for the manufacture of chemicals

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21
Q

What is formed when a hydrocarbon is burnt completely? What is the colour and temperature of the flame?

A

Carbon dioxide and water. The flame is blue with a high temperature. Very little (not none) soot is produced.

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22
Q

What is formed when a hydrocarbon is burnt incompletely?

A

Soot, unburnt carbon particles, are produced, as well as carbon and carbon monoxide.

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23
Q

What is the colour and temperature of the flame when a hydrocarbon is burnt incompletely?

A

The flame is yellow or orange with a low temperature.

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24
Q

What are the sources of air pollution and what makes them pollute? (3 sources)

A
  1. Exhaust of motor vehicles - burning of petrol or diesel oil
  2. Power plants and factories - burning of coal or petroleum fractions to produce energy
  3. Incinerators - burning waste
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25
Q

What are the 2 main types of air pollutants?

A

Gases and small solid particles

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26
Q

How is carbon monoxide formed? Where does it come from?

A

It is formed when fossil fuels are burned incompletely. Most of the carbon monoxide comes from motor vehicles.

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27
Q

State the colour, odour, and property of CO.

A

It is toxic, colourless and odourless.

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28
Q

What are the negative effects of low conc. of CO on a person?

A

Dizziness and headache

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29
Q

Why is CO toxic?

A

Haemoglobin in blood combines with carbon monoxide more strongly than with oxygen. Thus, carbon monoxide reduces the oxygen-carrying capacity of blood

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30
Q

Why is SO2 formed from the burning of fuels?

A

Most fuels contain sulphur.

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31
Q

What is the smell of sulphur dioxide and its acidity/alkalinity?

A

SO2 is an acidic gas with a choking smell.

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32
Q

What are the harmful effects of sulphur dioxide on humans?

A

It irritates our eyes and attacks our respiratory system, causing lung diseases.

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33
Q

What are the harmful effects of sulphur dioxide on the environment?

A

It causes acid rain.

34
Q

What are NO and NO2 collectively called?

A

Nitrogen oxides, NOx.

35
Q

How is nitrogen monoxide formed?

A

Nitrogen monoxide is formed from nitrogen and oxygen molecules in air due to the high temperature of the car engine.

36
Q

How is nitrogen dioxide formed?

A

The nitrogen monoxide formed from car engines rapidly reacts with oxygen in air to form nitrogen dioxide.

37
Q

What is the smell, colour, acidity/basicity of NO2?

A

Nitrogen dioxide is an brown acidic gas with an irritating smell.

38
Q

What are the harmful effects of nitrogen oxides on the human body? (3 points)

A

Nitrogen oxides are poisonous, irritate our eyes and attack our respiratory system.

39
Q

What are the harmful effects of nitrogen oxides on the environment? (2 points)

A

They cause acid rain and photochemical smog.

40
Q

What are the sources of nitrogen oxides?

A

Cars, power plants, and factories.

41
Q

What is the main source of unburnt hydrocarbons?

A

Motor Vehicles

42
Q

What are the harmful effects of unburnt hydrocarbons on the human body?

A

They irritate our respiratory system. Some are suspected of causing cancer.

43
Q

What are the harmful effects of unburnt hydrocarbons on the environment?

A

They are involved in the formation of photochemical smog.

44
Q

What are suspended particulates? Give 3 examples.

A

Suspended particulates are solid particles that remain suspended in the air for a long time. These include black smoke (fine carbon particles), dust, and soot (coarse carbon particles).

45
Q

What are the 6 sources of suspended particulates?

A
  1. Motor vehicles
  2. Factories
  3. Power plants
  4. Incinerators
  5. Construction Sites
46
Q

What are the harmful effects of suspended particulates on the human body? (2 points)

A

Small suspended particulates can enter our lungs and irritate our respiratory system. Many of them also cause lung cancer.

47
Q

What are the harmful effects of suspended particulates on cities? (2 points)

A

They reduce visibility and darken building walls.

48
Q

What does leaded petrol contain and what is its chemical formula? What is the purpose of adding it to petrol?

A

Tetraethyllead(IV), Pb(C2H5)4. It is used to improve fuel combustion.

49
Q

What pollutant does leaded petrol produce?

A

Combustion products from leaded petrol produce lead compounds as part of the suspended particulates.

50
Q

What are the harmful effects of leaded petrol on the human body? (3 points)

A

They can cause anaemia, ie decrease in the no. of red blood cells. They can also damage our nervous system, esp. in children. Lead can also accumulate in our body and cause poisoning effects.

51
Q

What is the pH of normal rain and acid rain?

A

Normal rain: 5.6, Acid rain, <5.6

52
Q

How is acid rain formed? List the chemical reactions. (3 steps)

A
  1. Sulphur dioxide dissolves in rainwater to form sulphurous acid.
    SO2 + H2O H2SO3
  2. Sulphurous acid further reacts with oxygen to produce sulphuric acid.
  3. Nitrogen oxides in the air dissolve in rainwater to form nitric acid and nitrous acid.
    2NO2 + H2O -> HNO2 + HNO3
    4NO + 2H2O + O2 -> 4HNO2
53
Q

Name two harmful effects of acid rain on plants.

A
  1. Acid rain makes the soil acidic, and plants cannot grow well in acidic soil.
  2. Acid rain damages the leaves of plants, affecting their ability to conduct photosynthesis.
54
Q

Name one harmful effect of acid rain on marine life.

A

Acid rain makes water in rivers and lakes acidic, and fish and water plants cannot survive in water which is too acidic.

55
Q

Which building materials does acid rain corrode?

A

Limestone, marble, sandstone, cement, and concrete.

56
Q

How does acid rain corrode at buildings? Use a chemical reaction.

A

CaCO3 + 2H+ -> Ca2+ + CO2 + H2O

57
Q

What effect does acid rain have on metal objects?

A

Acid rain corrodes metal objects, including underground metal pipes.

58
Q

Why is rain more acidic during winter? List 2 possible reasons.

A
  1. Solubility of gases increase with decreasing temperature. More acidic gases dissolve in rainwater to form acid rain.
  2. People typically use more energy in winter. More fuels are burnt to meet the demand.
59
Q

Given that the atmosphere of Venus contains mainly carbon dioxide, would the average temperature on Venus be higher or lower than that on Earth?

A

Carbon dioxide is a greenhouse gas. The temperature would be higher.

60
Q

Explain the greenhouse effect. (4 Steps)

A
  1. Energy from the sun falls on the earth.
  2. Half of the energy is absorbed, warming the atmosphere and the Earth’s surface.
  3. Earth reradiates most of the absorbed energy into space as infrared radiation.
  4. Greenhouse gases hold back some of this radiation, and the earth gets warmer.
61
Q

List a few examples of greenhouse gases.

A

Carbon dioxide, water vapour, methane, CFCs, nitrogen oxides, ozone.

62
Q

Explain how global warming is related to the greenhouse effect.

A

When humans burn fossil fuels, carbon dioxide, a greenhouse gas is released. This contributes to the greenhouse effects. This causes a rise in the average temperature of the earth, global warming.

63
Q

List 2 ways methane is produced.

A

The remains of plants especially in rice paddies as well as the manure of animals in cattle farms give out methane when they decay.

64
Q

List 3 harmful effects of global warming.

A
  1. Melting of ice at the poles, causing an increase in average sea levels. This may cause flooding in low-lying coastal areas.
  2. Climate change, damaging agriculture and reducing the food supply.
  3. Putting wildlife in danger
65
Q

List 3 ways to tackle global warming. (Total 5)

A
  1. Using alternative energy
  2. Stop Deforestation
  3. Plant more trees
  4. Putting out forest fires
  5. Collecting methane from decaying plant and animal wastes and using it as fuel.
66
Q

What are the 5 main problems associated with oil spillages?

A
  1. Floats on water, blocking oxygen supply to aquatic life.
  2. Poisonous to aquatic life
  3. Stops sea birds from flying
  4. Oil is flammable, burning with a very sooty flame. This produces air pollution.
  5. Use of detergent to clean up spilt oil has other bad effects on aquatic life.
67
Q

List 1 way to cut down on lead emission.

A

Using unleaded petrol

68
Q

What is a catalytic converter?

A

It is a stainless steel cylinder containing a catalyst, platinum or rhodium, and attached to the exhaust pipe.

69
Q

What is the working principle of a catalytic converter? Use chemical reactions.

A

2CO + 2NO -> 2CO2 + N2 (Pt(s) / Rh (s))
2CO + O2 -> 2CO2 (Pt(s) / Rh (s))
CxHy + (x+y/4)O2 -> xCO2 + y/2H2O

70
Q

What pollutants are catalytic converters effective against?

A

Carbon monoxide, nitrogen monoxide, and unburnt hydrocarbons.

71
Q

Why can a catalytic converter only work efficiently on unleaded petrol.

A

The catalytic converter is poisoned and made ineffective by lead and its compounds.

72
Q

Name 2 ways to reduce the emission of air pollutants for vehicles using diesel.

A

Diesel catalytic converters and particulate traps.

73
Q

Suggest a way to reduce suspended particulates and nitrogen oxides.

A

Using LPG instead of diesel oil.

74
Q

Suggest 2 ways to reduce the emission of sulphur dioxide.

A
  1. Use fuels with low sulphur content.

2. Scrubbers

75
Q

Explain the working principle of scrubber, with the aid of a chemical equation.

A

Waste gases are sprayed with limewater, which reacts with sulphur dioxide and removes it.
Ca(OH)2 + SO2 -> CaSO3 + H2O

76
Q

Suggest another way other than scrubbers to reduce sulphur dioxide emissions in a power plant.

A

A flue gas desulphurisation system.

77
Q

Suggest why scrubbers cannot be used in motor vehicles.

A

It is too big

78
Q

Suggest a way to remove suspended particulates from industrial emission and explain its working principle.

A

Electrostatic precipitators. Suspended particulates pass through a strong electric field, becoming negatively charged. They are later removed through positively charged plates.

79
Q

Suggest a way to remove dust from industrial emission.

A

Mechanical filtering.

80
Q

Suggest four energy sources currently used in power plants in Hong Kong to generate electricity.

A

Nuclear energy, wind energy, natural gas and coal.

Chemistry (2 decks)

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