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Chemistry (AS Chemistry) Flashcards on Resources, created by nicole_j_baldwin on 03/22/2015.

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Question Answer
Briefly describe the greenhouse effect: Radiation from the sun reaches planet Radiation absorbed and re-emmitted as IR radiation Absorbed by gases Gases reemit IR radiation as energy
Name the three greenhouse gases Water vapour - H2O Methane - CH4 Carbon dioxide - CO2
How do gases absorb radiation? BONDS VIBRATE Different gases absorb different amounts of IR radiation.
What three factors determine the impact of a greenhouse gas? 1. Its CONCENTRATION in the atmosphere (relative abundance) 2. It's ABILITY to ABSORB IR radiation 3. It's LIFETIME in the atmosphere
What does GWP stand for? Global Warming Potential. Consists of three factors
Renewable resources Alternative energy sources like wind, solar, tidal and nuclear reduce CO2 pollution. Fossil fuels necessary to meet energy demands
Carbon Capture Storage (CCS) STORAGE OPTION CO2 can be captured and stored to reduce pollution: - In disused oil refineries -Deep in oceans - In underground deposits
Carbon Capture Storage (CCS) REACTION OPTION Mineral storage reduces CO2 by converting it to minerals such as carbonates: CaO + CO2 ==>> CaCO3
Ozone layer benefits: Acts like "sunglasses" filtering out harmful radiation (UV-c)
Ozone formation: uv O2 ==> 2O* The radical reacts with an O2 molecule forming O3 O* + O2 ==> O3 (+heat)
How does the ozone layer work? Ozone absorbs UV radiation breaking it into O2 and O. O and O2 then react reforming O3 and producing heat. Overall UV is converted to heat energy and this process continues creating an equilibrium: O + O2 <==> O3
Ozone depletion INITIATION UV radiation breaks C--Cl bonds releasing chlorine radicals into the atmosphere. CFCl3 ==> CFCl2* + Cl*
Ozone depletion PROPOGATION Cl* + O3 ==> ClO* + O2 ClO* + O ==> Cl* + O2 overall: O + O3 ==> 2O The chlorine radicals catalyse the decomposition of ozone with the chlorine radical coming out unchanged.
Ozone Depletion: *NO Nitrogen oxide is formed from lightening strikes and aircraft engines. Reaction mechanism similar to chlorine radicals but with nitrogen oxide radicals.
Air pollution: CO Carbon monoxide: - poisonous, reduces oxygen levels in blood - reduces ability to perform complex tasks
Air pollution: NOx Nitrogen oxides: - Formed at high temperatures in a car engine/exhaust. - produces low level ozone (respiratory problems) - Acid rain
Air pollution: VOCs Volatile organic compounds: - unburnt fuels released in exhaust fumes - can be carcinogenic - react with NO2 forming low-level ozone
Catalytic converters 2 types Honeycomb structure increases surface area (1) Oxidation catalytic converters (convert CO to CO2 and oxidise VOCs) (2) 3-way catalysts (convert CO to CO2 removes NO and oxidises VOCs)
How does a catalyst work? HETEROGENOUS: ADSORPTION: Molecules held to surface REACTION: Temporary bonds form. Molecule's bonds weaken. Reaction occurs. DESORPTION: Products desorbed from catalyst. Diffuse away.
What are the 12 principles of sustainability? 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. CATALYSTS 10. Design for DEGRADATION 11. Real time analysis for POLLUTION prevention 12. Inherently saver chemistry for ACCIDENT PREVENTION
CO2 villain to saviour: Outline uses for CO2 1. In foam. Used as a replacement to CFCs to expand polystyrene 2. Solvent. Can be turned to scCO2 and then used to dissolve other chemicals. 3. Decaffeinating coffee 4. Producing fizz in beer 5. Dry cleaning 6. Chemical synthesis 7. Toxic waste treatment
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