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19 Cards in this Set
- Front
- Back
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Describe how infrared radiation is absorbed by bonds in CO2, H2O and CH4 and explain how this contributes to the global warming.
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The CO2 molecule can absorb infrared radiation causing the molecule to vibrate, the vibrating molecule emits some of this energy in the form of radiation. This can then be absorbed by another greenhouse gas molecule or at the Earth's surface. In the similar way the O-H bond in H2O and C-H bond in CH4 absorb the infrared radiation. The absorption-emission process keeps the heat close to the Earth's surface.
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Define greenhouse effect.
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It is 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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Explain how the greenhouse effect of a given gas is dependent on its atmospheric concentration and ability to absorb infrared radiation.
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The ability of a trace gas to cause global warming is described by its Global Warming Potential (GWP). GWP is related to the lifetime of the gas in the atmosphere, its abundance and the its ability to absorb infrared radiation. The greenhouse effect of a given gas is dependent of its atmospheric concentration as the more of it in the atmosphere the more it can react and the easier it is for it to absorb infrared radiation the more reactive it is in the atmosphere and the more heat it traps.
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Explain the importance of controlling global warming caused by atmospheric increases in greenhouse gases.
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The emission of CO2 has increased compared to 1990 levels. This increase leads to more heat being trapped near the Earth's surface and this in turn leads to consequences such as melting ice caps, violent storms, floods, draughts and many more. In order to avoid these changes in our climate we need to be able to control the abundance of greenhouse gases in the atmosphere.
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Outline the role played by chemists through the provision of scientific evidence that global warming is taking place.
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In Arctic the ice and permafrost are disappearing, in Antarctic the ice sheet is melting into the oceans, tropical areas are experiencing more frequent and destructive storms and floods. In Europe the glaciers are disappearing and there have been extreme heat waves. The vast majority of scientist now are agreeing that human activity is contributing to the global warming however there are some which still believe that it is a part of a natural cycle. We need the opinion of scientists to be able to take appropriate steps when necessary in order to save out planet.
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Explain the Kyoto protocol and the EU initiatives.
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The Kyoto protocol committed countries to reduce their emission of CO2 by 5% by 2012. 100 countries signed up to the protocol however the biggest emitter- US didn't. In 2006 about 25% of the CO2 in the atmosphere was coming from US, in order to lower the levels of CO2 US would have to join in.
The EU initiatives are: - At least 20% of energy used in EU will come from renewable sources by 2020. - At least 10% of the fuels used in transport will be biofuels by 2020. - EU greenhouse gas emission will be reduced by 20% below 1990 levels by 2020. |
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Outline Carbon Capture and Storage (CCS).
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CCS captures carbon dioxide from power stations and stores it safely instead of it being released into the atmosphere. It is an immediate strategy to get rid of waste CO2 and the Earth has many safe places to store the captured CO2 such as underground porous rocks which can act as a sponge as well as old oil and gas fields.
Scotland is developing a project in which electricity would be manufactured from natural gas. They would react CH4 with H2O to produce H2 and CO2 which would be collected and piped offshore to an oilfield which is nearing the end of its productive life. It is very hard to extract the last 30% of the oil from an oilfield, however the CO2 pumped in will enable the remaining oil to be extracted. This would be a benefit as the oil extraction would be easier and CO2 would be stored deep in the ocean. |
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Outline carbon storage in deep geological formations by reaction with metal oxides to form stable carbonate materials.
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CO2 would be trapped by conerting it into a carbonate rock. To do this CO2 would be reacted with a metal oxide such as CaO or MgO to form CaCO3 or MgCO3. This process occurs naturally and has produced much of our limestone and calcium carbonate rock however the natural reaction is very slow. Any efforts to increase the rate of the reaction are very energy intensive.
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Explain how ozone can be good and bad at the same time.
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Ozone is an O3 molecule and whether it is good or bad depends on where it is in the atmosphere.
When it is in the troposphere (lowest layer of the Earth's atmosphere) it is bad as it is an air pollutant with harmful effects on the respiratory system of animals. However when ozone is in the stratosphere (second layer of the Earth's atmosphere) it is good as it protects living organisms by preventing harmful ultraviolet light from reaching the Earth's surface. |
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Outline the role of ozone in the absorption of harmful ultraviolet radiation and the resulting benefit for life on Earth.
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There are three types of UV radiation based on the wavelength of the radiation; UV-a the longest and not as damaging, UV-b can cause sunburn and sometimes genetic damage, which can result in skin cancer, if exposure is prolonged (most of UV-b radiation is screened out by the ozone layer) and UV-c which is entirely screened out by the ozone layer. The most harmful UV radiation is screened out by the ozone layer and therefore the ozone layer protects the life on Earth from harm.
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Explain how ozone is continuously being formed and broken down in the stratosphere by ultraviolet radiation and how it can be removed.
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An o2 molecule is broken down by the UV radiation into two O atoms. The O atoms then react with the O2 molecules to form ozone; O3. This process generates heat. The ozone layer absorbs UV and in this process O3 molecules are broken back to O2 molecules and O atoms, this is the reverse of the reaction of ozone formation. The reaction creates a cycle as O3 is broken down into O2 molecules and O atoms which react to form O3 molecules. This cycle keeps the ozone layer in stable balance and protects living organisms from the harmful effects of high-energy UV radiation. Ozone is removed when an O3 molecules react with O atoms to form two O2 molecules. The removal rate however is slow as the concentration of O atoms is low.
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How do radicals from CFCs and NOx may catalyse the breakdown of ozone.
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CFCl3 is broken down by UV into a Cl radical and a CFCl2 radical (initiation).
Then the Cl radical reacts with O3 to make O2 and ClO radical which then further reacts with O atoms to make more Cl radicals and O2 molecules. Overall these two propagation steps cancel down to O3+O2---> 2O2 NO acts in a very similar way: 'NO+ O3 ----> 'NO2+ O2 'NO2+ O ----> 'NO + O2 which overall also cancels down to: O2+ O ----> 2O2 |
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Explain the formation of carbon monoxide, oxides of nitrogen and unburnt hydrocarbons from the internal combustion engine.
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Carbon monoxide is emitted from the incomplete combustion of hydrocarbons and other organic compounds. Carbon monoxide molecules can stay in the atmosphere for about a month before being oxidised to CO2.
During the burning of fuels in the internal combustion engine air is drawn into the cylinder along with the fuel. The fuel is burnt in the presence of oxygen generating energy, however some nitrogen oxides are produced as nitrogen from the air is oxidised by the oxygen. Two oxides of nitrogen are produced NO and NO2. Volatile Organic Compounds (VOCs) are release in vehicle exhausts, usually from unburnt fuels. |
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State environmental concerns relating to the toxicity of carbon monoxide, oxides of nitrogen and unburnt hydrocarbons and their contribution to low-level ozone and photochemical smog.
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CO is a poisonous gas. CO can bind strongly to haemoglobin reducing the amount of oxygen supplied to tissues and organs.
NO2 contributes to formation of low level ozone. Much on NO2 is converted into nitric acid, a contributor to acid rain. No is a respiratory irritant and even low levels affect the asthmatics. VOCs and NO2 react together to form low-level ozone. The mechanism leading to ozone formation involves radicals and the energy needed for the reaction is provided by sunlight. Low-level ozone is a serious pollutant causing breathing difficulties and increasing susceptibility to infections. |
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Outline how a catalytic converter decreases toxic emission via adsorption, chemical reaction and desorption.
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Oxidation catalysts are used in diesel engines to decrease emission of carbon monoxide and VOCs. The second type of catalytic converter is known as three-way catalyst and it is fitted in petrol engines. It removes NO and CO to form N2 and CO2.
A catalyst provides a large surface area over which the reaction takes place. The CO and NO molecules diffuse over the catalytic surface of the meta; and some molecules are help to the metal surface (adsorption). This allows the molecules to be held in a right position so that the reaction can occur and CO2 and N2 can be produced and desorbed from the surface. These then diffuse away from the catalytic system. |
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What kind of spectroscopy can help to monitor air pollution?
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Infrared spectroscopy.
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Describe principles and discuss issues of chemical sustainability.
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Sustainability means the development of processes that prevent the depletion of natural resources.
The 12 principles are: 1) Prevention 2) Atom Economy 3) Less hazardous chemical synthesis 4) Design safer chemicals 5) Safer solvents and auxiliaries 6) Design for energy efficiency 7) Use of renewable feedstocks 8) Reduce derivatives 9) Catalysis 10) Design for degradation 11) Real-time analysis for pollution prevention 12) Inherently safer chemistry for accident prevention |
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Discuss some of the ways of reducing CO2 emissions into the environment.
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CO2 can be collected and used.
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Outline some of the positive benefits of using CO2 as a substitute for more harmful materials.
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CO2 in a foam replaces CFCs. CO2 as a solvent, when we alter the temperature and pressure we can get a liquid CO2 called supercritical fluid- scCO2. ScCO2 can be used to decaffeinate coffee, produce the natural fizz in beer and extract the characteristic flavour of beer from hops, it can be used for dry cleaning, toxic waste treatment because many organic compounds dissolve in scCO2 and it can also be used for chemical synthesis as the ability to control its solvent properties means that desired product is obtained with fewer co-products.
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