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Chem 2: Developing Fuels > DF10 - The Trouble With Emissions > Flashcards

DF10 - The Trouble With Emissions Flashcards

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1
Q

What are the main pollutants from vehicle engines?(6)

A
  • Carbon dioxide
  • Carbon monoxide
  • Hydrocarbons
  • Nitrogen Oxide
  • Particulates
  • Sulfuric Oxides
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2
Q

How is carbon dioxide formed from vehicle engines?

A

Complete combustion of hydrocarbons (e.g alkanes, alkenes, alcohols, cycloalkanes)

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3
Q

Why do hydrocarbons make good fuels?

A

Combustion is a very exothermic reaction

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4
Q

What problem does carbon dioxide cause?

A

The greenhouse effect

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5
Q

What is the greenhouse effect?(3)

A
  • Earth radiates IR into space
  • Greenhouse gases absorb some of this and reflect it back
  • The build up of CO2 causes an enhanced greenhouse effect, leading to global warming
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6
Q

What problems does global warming cause?(3)

A
  • Destruction of habitats e.g ice cap meltings, leading to species extinction
  • Sea level rising
  • Freak, stronger storms
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7
Q

How is carbon monoxide formed from vehicle engines?

A

Incomplete combustion of hydrocarbons (e.g alkanes, alkenes, alcohols, cycloalkanes) due to a limited air supply

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8
Q

What problem does carbon monoxide cause for humans and why?

A
  • Poisoning and internal suffocation
  • CO molecules are chemically and physically similar to oxygen molecules
  • They can bind to the same sites on haemoglobin molecules in red blood cells as oxygen molecules
  • Carbon monoxide molecules are better at binding to haemoglobin molecules
  • So less oxygen can be carried around the body
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9
Q

How are hydrocarbons emitted from vehicle engines?

A

Engines don’t burn all the fuel molecules, so some come out as unburnt hydrocarbons

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10
Q

How is nitrogen oxide formed from vehicle engines?

A

High temperature and pressure in a car engine causes nitrogen and oxygen in the air to react together

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11
Q

How does nitrogen oxide contribute to the problem of acid rain?

A

It reacts with water and oxygen in the atmosphere to form nitric acid

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12
Q

What problems does nitrogen oxide cause?

A
  • Acid rain

- Photochemical smog

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13
Q

What are particulates?

A

Small carbon particles below 2.5x10^-12 m

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14
Q

Where do particulates come from?

A
  • By the incomplete combustion of hydrocarbons in engines
  • Power stations
  • Volcanoes
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15
Q

What problems do particulates cause?

A
  • Can settle in people’s lungs and cause problems e.g decreased lung function and airway irritation
  • Cardiovascular problems e.g heart attacks and strokes
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16
Q

Where does sulphur dioxide come from?

A
  • The burning of sulphur impurities in fuels

- Volcanoes

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17
Q

How does sulphur dioxide contribute to acid rain?

A

Sulphur dioxide gas enters the atmosphere and reacts with the moisture in it to form sulphuric acid
SO2+H2O==>H2SO3

18
Q

What problems does acid rain cause? (4)

A
  • Breathing difficulties
  • Corrodes limestone buildings and statues
  • Kills forests
  • Kills life in lakes
19
Q

Define a “secondary pollutant”

A

A pollutant not released directly into the atmosphere

20
Q

How is photochemical smog formed?

A

Primary pollutants e.g hydrocarbons and nitrogen oxides react in the presence of sunlight to form secondary pollutants e.g ozone

21
Q

What problems does photochemical smog cause? (3)

A
  • Haziness and reduced visibility in the air
  • Respiratory problems
  • Eye irritation
22
Q

What way (other than catalytic converters) can carbon monoxide emissions be reduced?

A

Oxygenates can be added to petrol

23
Q

Why is a catalytic converter described as being “3-way” (and what pollutants does it reduce)?

A

It reduces 3 pollutants:

  • Carbon monoxide
  • Hydrocarbons
  • Nitrogen monoxide
24
Q

What do catalytic converters consist of?

A

Platinum/rhodium on a porous support

25
Q

Give the word equation for the reduction of carbon monoxide

A

2CO+O2====> 2CO2

26
Q

Give the word equation for the reduction of heptane

A

C7H16 +11O2 ====> 7CO2 + 8H2O

27
Q

Give the word equation for the reduction of nitrogen monoxide

A

2NO + CO =====> N2 + 2CO2

28
Q

How do catalytic converters work?

A

They reduce harmful pollutants into less harmful ones

29
Q

Why does reducing nitrogen monoxide not work in diesel engines?

A

They have a higher concentration of oxygen so any reducing agent would be oxidised

30
Q

What two types of catalysts are used in catalytic converters?

A
  • Platinum

- Platinum alloyed with rhodium

31
Q

What temperature would a platinum catalyst need to work?

A

240 degrees c

32
Q

What temperature would a platinum alloyed with rhodium catalyst need to work?

A

150 degrees c

33
Q

What type of fuel would a platinum rhodium alloy catalyst need to work and why?

A

Lead free fuel as lead would poison it

34
Q

What two ways are there to remove nitrogen oxides in diesel engines?

A
  • Reducing it by recycling exhaust gases through the cylinder, lowering temperature and thus the amount of NOx formed
  • Using ammonia as a catalyst instead
35
Q

Give the formula for using ammonia as a catalyst for reducing nitrogen oxides

A

4NO + 4NH3 + O2 ===> 4N2 + 6H2O

36
Q

What two ways are there to remove sulfur oxides?

A
  • Using ultra low sulfur fuels

- Using calcium oxide to remove them from power station emissions

37
Q

How are particulates removed from power station emissions?

A

Using wet scrubbers

38
Q

How are particulates removed from car exhausts?

A

Using diesel particulate filters

39
Q

What do diesel particulate filters contain?

A

A variety of materials, the most common being ceramic

40
Q

What methods can the government take to reduce overall pollution? (2)

A
  • Changing laws to reduce emissions e.g vehicles not allowed to pollute above a certain level
  • Taxing pollution more highly e.g raise taxes on fuel
41
Q

How can the population reduce overall pollution?

A

By changing their behaviour e.g car shares

42
Q

What are the largest sources of air pollutants? (3)

A
  • Transport
  • Industry
  • Power generation

Chem 2: Developing Fuels (11 decks)

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