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Chemistry > Air quality > Flashcards

Air quality Flashcards

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1
Q

What is the composition of air

A
  • 78% N2
  • 21% O2
  • 1% noble gases
  • 0.03% CO2
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2
Q

What are some common atmospheric pollutants

A
  • CO
  • NO
  • NO2
  • O3
  • CH4
  • SO2
  • Unburned hydrocarbons
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2
Q

In fractional distillation, which substance is removed from the top

A

Lowest boiling point

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3
Q

What are the sources of CO

A

Incomplete combustion of carbon-containing fuels

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3
Q

What are the harmful effects of SO2

A
  • Causes eye irritation and breathing difficulties
  • Causes acid rain which destroys aquatic life, damages vegetation, and corrodes metal, limestone and marble structures
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4
Q

What are the sources of SO2

A
  • Combustion of fossil fuels that contain sulfur as impurities
  • Volcanic eruptions
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5
Q

What are the harmful effects of CO

A
  • Binds permanently with haemoglobin to form carboxyhaemoglobin, reducing ability of red blood cells to transport oxygen
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6
Q

How to prevent or treat CO pollution

A
  • Fit motor vehicles with catalytic converters
  • Catalytic converters oxidise CO to CO2
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7
Q

How to prevent SO2 pollution

A
  • Remove sulfur impurities from fossil fuels
  • Flue gas desulfurisation
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8
Q

What is flue gas desulfurisation

A
  • Waste gases including SO2 known as flue gases
  • Waste gases treated with wet mixture of CaCO3
  • SO2 reacts with wet CaCO3 to form CO2 and calcium sulfite
  • CaSO3 is further oxidised with O2 to form CaSO4
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9
Q

What are the harmful effects of NO and NO2

A
  • Causes eye irritations and breathing difficulties
  • Produces acid rain
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9
Q

What are the sources of NO and NO2

A
  • Internal combustion of motor vehicles when N2 and O2 from air react at high temperature
  • Occurs naturally from lightning activity as heat released by lightning allows oxygen and nitrogen in air to react
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10
Q

How to prevent and treat NO and NO2 pollution

A
  • Fit motor vehicles with catalytic converters
  • Catalytic converters reduce NO and NO2 to N2
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11
Q

How is acid rain formed

A
  • SO2 reacts with oxygen and water vapour in air to form H2SO4
  • NO2 reacts with oxygen and water vapour in air to form HNO3
  • Typical acid rain is at pH 4
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12
Q

What are hydrocarbons

A

Compounds that contain hydrogen and carbon only

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13
Q

How do motor vehicles cause pollution

A
  • Hydrocarbons undergo complete combustion in excess oxygen to form CO2 and water vapour
  • Hydrocarbons undergo incomplete combustion in limited oxygen to form CO and water vapour
  • N2 and O2 react at high temperature to form NO and NO2
14
Q

What are catalytic converters

A
  • Contain ceramic elements coated with platinum and rhodium catalysts
  • Enclosed by stainless steel casing
15
Q

How do catalytic converters reduce pollution

A
  • CO oxidised to CO2
  • NO and NO2 reduced to form N2
  • Unburned hydrocarbons oxidised to form CO2 and H2O

Oxidation with oxygen, reduction with carbon

16
Q

What are other ways to reduce air pollution by motor vehicles

A
  • Use cleaner fuels like hydrogen
  • Use electric vehicles
17
Q

What processes is the carbon cycle made up of

A
  • Respiration
  • Combustion
  • Decomposition
  • Photosynthesis
  • Ocean uptake
17
Q

What are the main greenhouse gases

A
  • CO2
  • CH4
18
Q

How is carbon dioxide produced

A
  • Respiration forms CO2 and water vapour
  • Combustion of fossil fuels produces CO2
  • Decomposition of plants and animals produces CO2
18
Q

How is carbon dioxide removed

A
  • Photosynthesis requires CO2 and H2O
  • Oceans act as huge sinks for CO2
19
Q

What are CFCs

A

chlorofluorocarbon molecules
- Compounds that contain only chlorine, fluorine and carbon
- Gases at r.t.p.
- Not broken down in ground-level atmosphere

20
Q

What are the sources of CFCs

A
  • Aerosol propellants
  • Coolants fluids for refrigerators and air-conditioners
21
Q

Why can 1 chlorine atom destroy 10000 ozone molecules

A

1) CFCl3 –> CFCl2 + Cl
2) Cl + O3 –> ClO +O2
3) ClO + O –> Cl + O2

  • Chlorine atom reacts with ozone molecules to form ClO and O2
  • UV breaks down O2, so ClO can react with O to form Cl again
  • Process repeats itself
22
Q

Describe the depletion of the ozone layer

A
  • Earth surrounded by layer of ozone gas 40km above ground level, protecting planet from UV rays
  • Ozone layer destroyed by chlorine atoms produced from CFCs
  • CFCs are decomposed by UV light from sun, forming reaction chlorine atoms
  • Chlorine atoms react with ozone molecules to form O2 and chlorine monoxide
  • Excessive UV light allowed to reach Earth

Chemistry (17 decks)

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