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A-level chemistry > AS - Unit 2 - Resources > Flashcards

AS - Unit 2 - Resources Flashcards

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1
Q

How does the Earth get most of its energy?

A

As electromagnetic radiation from the Sun

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2
Q

What is the greenhouse effect?

A

The process in which the absorption and subsequent emission of infrared radiation by atmospheric gases warms the lower atmosphere and the planet’s surface

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3
Q

Give three natural processes which produce carbon dioxide

A

Volcanic eruptions
Respiration of animals
Burning or decay of organic matter, such as plants

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4
Q

What is the third most abundant greenhouse gas?

A

Methane

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5
Q

Give three ways methane is produced and released into the atmosphere

A

It is;
emitted during the production of coal, natural gas and oil
A product of rotting organic waste in landfill sites
Released from certain animals, especially cows, as a by-product of digestion

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6
Q

In water which bonds absorb infrared radiation?

A

the O-H bonds

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7
Q

In methane which bonds absorb infrared radiation?

A

the C-H bonds

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8
Q

Give 4 examples of the evidence of global warming on Earth

A

Ice and permafrost disappearing in the Arctic
Ice sheet melting into the oceans in the Antarctic
Tropical areas experiencing more frequent and destructive storms and floods
Glaciers are disappearing and extreme heat waves in Europe

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9
Q

What 5 unpredictable changes has global warming brought to earth?

A

Rivers overflow due to excessive rainfall, in others drought-like conditions lead to water shortages
Longer growing season improving crop yield, but in others there is drought and disease ruining harvests
Storms and hurricanes are becoming more extreme, frequent and destructive
Sea ice in the Arctic is melting faster each year, fears that the Gulf Stream current may be cut off, leading to severe winters in northern Europe, including the UK
Increasing temperatures expend the water in the oceans. Together with extra water from melting land ice, sea levels are rising. If the Greenland ice sheet and the Antarctic glaciers where to melt, sea levels would rise by 6 metres, flooding land populated by millions of people

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10
Q

What three targets were agreed within the EU regarding global warming?

A

20% of energy used in the EU will come from renewable sources by 2020
10% of the fuels used in transport will be biofuels by 2020
EU greenhouse gas emissions will be reduced to 20% below 1990 levels by 2020

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11
Q

Give 4 ways of producing energy more cleanly

A

Wind turbines
Tidal power
Solar panels
Nuclear plants

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12
Q

What is the troposphere?

A

The lowest layer of the Earth’s atmosphere, extending from the Earth’s surface up to about 7km (above the poles) and to about 20km (above the tropics)

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13
Q

What is the stratosphere?

A

The second layer of the Earth’s atmosphere, containing the ‘ozone layer’, about 10km to 50km above the Earth’s surface

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14
Q

Where in the atmosphere is ozone good and where is it bad?

A

Bad: ozone near to the Earth’s surface in the troposphere is in air pollutant with harmful effects on the respiratory systems of animals
Good: ozone in the upper atmosphere in the stratosphere protects living organisms by preventing harmful UV light from reaching the Earth’s surface

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15
Q

How does the ozone layer help to protect living organisms on Earth?

A

It filters out the shorter UV light wavelengths, which are harmful to living organisms (less than 320nm) and converts this UV radiation into heat

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16
Q

What are the three different types of UV radiation?

A

UV-a
UV-b
UV-c

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17
Q

What is UV-a?

A

It has a wavelength of 320-400nm
It reaches the Earth’s surface, has less energy than the shorter wavelengths as is not as damaging
UV-a radiation doesn’t cause us much concern

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18
Q

What is UV-b?

A

It has a wavelength of 280-320nm

It can cause sunburn and sometimes genetic damage, which can result in skin cancer if exposure to UV-b is prolonged

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19
Q

What is UV-c?

A

It has a wavelength of 200-280nm

It is completely screened out by the ozone layer

20
Q

Why is it a worry that the ozone layer is depleting in regards to UV-b?

A

Any decrease in the ozone layer would allow more UV-b radiation to reach the surface of the Earth. This would cause increased genetic damage to living organisms

21
Q

How is ozone formed?

A
  1. O2 molecules absorb a wavelength of less than 240nm
    This high-energy radiation is capable of breaking an O2 molecule into two oxygen atoms
    O2 + (radiation < 240nm) –> 2O
  2. The O atoms then react with O2 molecules to form ozone molecules
    O2 + O –> O3 + heat
22
Q

How does the ozone layer work?

A

The ozone layer is broken down by wavelengths of 310nm turning O3 into O2 and O

O3 + (radiation < 310nm) –> O2 + O

The O atom then immediately reacts with O2 molecules in the ozone later:

O2 + O –> O3 + heat

And the cycle continues, this cycle keeps the ozone layer in a stable balance and a natural steady state is reached in which ozone is being formed at the same rate as it is being broken down

O2 + O O3

23
Q

What is the removal of ozone?

A

When an oxygen atom and an ozone molecule combine they form two O2 molecules
Luckily the removal rate is slow since the concentration of O atoms is very low
However human activity can affect this balance.

24
Q

How do CFCs destroy the ozone layer?

A

When CFCs reach the ozone layer the C-Cl bond is broken by the UV radiation from the sun
This produces a Cl radical
Cl radicals are extremely reactive and once in the ozone layer can react with the ozone and break it down
Cl + O3 –> ClO + O2
ClO + O –> Cl + O2
where the overall equation is O3 + O –> O2
The Cl radical is regenerated at the end and continues to break down ozone again and again in a cycle

25
Q

What else can destroy ozone other than CFCs?

A

Nitrogen oxide from lightning or aircraft engines

26
Q

What three main things are emitted from internal combustion engines?

A

Carbon monoxide
Oxides of nitrogen
Unburnt hydrocarbons

27
Q

Give some facts about carbon monoxide

A

Poisonous gas, produced from the incomplete combustion of hydrocarbons.
Majority of carbon monoxide production comes from traffic pollution in urban areas
Can exist in the environment for one month before being oxidised to carbon dioxide
For humans, the haemoglobin in our blood carries oxygen to our tissues, carbon monoxide binds strongly to this haemoglobin reducing the amount of oxygen supplied to tissues and organs.

28
Q

Give some facts about oxides of nitrogen

A

Produced in the high temperature process where air is drawn into the cylinder along with fuel in the internal combustion engine. They are made by some of the nitrogen in the air being oxidised by the oxygen.
The two oxides of nitrogen are:
Nitrogen monoxide
Nitrogen dioxide
high concentration of these gases in urban areas with high traffic levels
Nitrogen dioxide is responsible for the formation of low level ozone, most of the NO2 is converted into nitric acid, a contributor to acid rain. They are also respiratory irritants.

29
Q

Which two unburnt hydrocarbon compounds are of particular concern and why?

A

Benzene
Buta-1,3-diene
Known to be human carcinogens

30
Q

Give some facts about unburnt hydrocarbons

A

Once released into the atmosphere, the unburnt hydrocarbons and nitrogen dioxide react together to form low-level ozone
The energy for this is provided by sunlight
The mechanism responsible for this involves radicals
Low-level ozone is a serious concern causing breathing difficulties and increasing susceptibility to infections
Conc of low-level ozone builds up on humid sunny days when the still air contains large quantities of hydrocarbons and oxides of nitrogen

31
Q

Explain the structure of a catalytic converter

A

It is made from platinum, rhodium, and palladium

It is supported on a honeycomb mesh. This is used to provide a large surface area

32
Q

How do catalytic converters work?

A

The hot exhaust gases pass over the catalytic surface and the harmful gases are converted to less harmful products. These are then released into the atmosphere

  1. The catalyst provides a surface on which the reaction takes place
  2. The CO and NO gas molecules diffuse over the catalytic surface of the metal. Some of the molecules are held on to the metal surface by adsorption
  3. Temporary bonds are formed between the catalytic surface and the gas molecules
  4. These bonds hold the gas molecules in the correct position on the metal surface, where they react together
  5. After the reaction, the CO2 and N2 products are desorbed from the surface and diffuse away from the catalytic surface
33
Q

What are the two types of catalytic converter typically in use?

A

Oxidation catalysts

Three-way catalyst

34
Q

In what vehicle is an oxidation catalytic converter used?

A

Used in vehicles with diesel engines to decrease emissions of carbon monoxide and unburnt hydrocarbons
They contain a complex filter system, and remove particulate matter and nitrogen oxides

35
Q

What reactions take place in an oxidation catalytic converter?

A

2CO(g) + O2(g) —-> 2CO2(g)

C12H26(l) + 18 1/2 O2(g) —-> 12CO2(g) + 13H2O(l)

36
Q

In what vehicle is a three-way catalytic converter used?

A

It is fitted in vehicles with petrol engines

In this system, nitrogen monoxide reacts with carbon monoxide to form the non-toxic gases nitrogen and carbon dioxide

37
Q

What reaction takes place in a three-way catalytic converter?

A

2NO(g) + 2CO(g) —-> N2(g) + 2CO2(g)

38
Q

What is adsorption?

A

The process that occurs when a gas, liquid or solute is held to the surface of a solid or, more rarely, a liquid

39
Q

What are the 12 principles of green chemistry?

A
  1. Prevention
  2. Atom economy
  3. Less hazardous chemical synthesis
  4. Designing safer chemicals
  5. Safer solvents and auxiliaries
  6. Design for energy efficiency
  7. Use of renewable feedstocks
  8. Reduce derivatives
  9. Catalysts
  10. Design for degradation
  11. Real-time analysis for pollution prevention
  12. Inherently safer chemistry for accident prevention
40
Q

How are green bags produced?

A

Bacteria is used to ferment vegetable oils and sugars in the waste and converts this into plastics
It took nearly 15 years to perfect this technique

41
Q

How are companies able to cut down on the amount of water and energy needed to produce what they need?

A

The use of catalysts

42
Q

How has ibuprofen become more ‘green’?

A

It was originally synthesised in 6 steps with less than 40% atom economy. A new way of producing ibuprofen has been developed where it has 3 catalytic steps and a 99% atom economy. And any waste produced is either recycled or is sold on as a useful by-product

43
Q

Give 7 ways CO2 can be used to be helpful to humans

A 
In foam
As a solvent
For decaffeinated coffee
For beer
For dry cleaning
Toxic waste treatment
Chemical synthesis
44
Q

How is CO2 used in foam?

A

CO2 has replaced CFCs as the blowing agent to produce foam. The company is using CO2 waste from industrial or natural sources, ensuring there is no net increase in global CO2.

45
Q

How is CO2 used for beer?

A

CO2 produces the natural fizz in beer, but can also be used to extract the characteristic flavour of beer from hops

A-level chemistry (15 decks)

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