Energy + Environment 8

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How does CO2 react with water to make carbonic acid, then bicarbonate, then carbonate?
CO2 forms weak acid solution in water. Released by biodegradation of organic matter in high concentrations. CO2+H2O<-> H2CO3 (carbonic acid)<-> HCO3- (bicarbonate ion) + H+ <-> CO3 2-(carbonate) +H+
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Why are the products of CO2 reactions equal in weight?
In the CO2 reactions as charges are equal the mols/litre must be equal for equal overall charge
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What is alkalinity and its formula?
Alkalinity is ability of water to neutralise acid. Includes bicarbonate (HCO3-), carbonate (CO3 2-) and hydroxide (OH-). Alkalinity = [HCO3-]+2[CO3 2-]+[OH]-
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Why is alkaline water important in nature?
A high alkalinity lake neutralises acid rain, pH stays 7-8, and aquatic life unharmed. Low pH lakes see pH drop and aquatic life die
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How do stalagmites and stalactites occur?
Dissolution and precipitation of carbonate rocks can occur leading to stalagmites and stalactites.
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How do CO2 and H2O react and how does this product lead to dissolution in the process of stalagmites and stalactites?
CO2 (from plant decay)+ H2O (dripping in caves) -> H2CO3 <-> H2CO3+CaCO3 (found in rocks, calcium carbonate) -> Ca 2+ +2HCO3-
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How is dissolved calcium then made into calcite?
Ca 2+ + 2HCO3- -> CaCO3 (calcite in stalagmite and stalactite) + CO2+H2O
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How can limestone build up?
Precipitation can lead to scales in hot water pipes, heater etc. Reduced solubility of CO2 at high temperature results in more loose CO2 and CaCO3 (Le Chatelier's principle)
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How do hard water and soap make scum?
Water hardness is caused by multivalent metallic cations such as Ca 2+ and Mg 2+. Hardness reacts with soap making scum. Sodium stearate (soap) reacts with Ca and Mg ions in hard water to form insoluble calcium and magnesium stearates (scum)
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Why is more soap needed in hard water regions?
Ca and Mg ions all have to all precipitate before layers of soap form, which is why more soap is needed in hard water areas.
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What is the equation for precipitation between soap and water?
Ca 2+ + 2C17H35COO- (sodium stearate) -> (C17H35COO)2Ca (calcium stearate)
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What are main atmosphere constituents?
N2 - 78%, O2 - 21%, Ar - 1%. Troposphere (lowest part) has constant concentration except water, and trace gas such as O, NO, halogens, radon, SO2 etc
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What are primary and secondary pollutants?
Primary pollutants are directly emitted (CO2, NO2), while secondary pollutants made in atmosphere reactions (ozone)
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What type of radiation does the sun most emit compared to Earth?
Incident solar radiation is 47% visible, 6% UV, rest mainly infrared, while Earth emits higher wavelength radiation back from Sun (mostly infrared)
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What is greenhouse effect?
Incoming solar radiation has some reflected at atmosphere, Earth's surface re-emits some infrared and some of this absorbed by greenhouse gases. CO2 and methane contribute most, then ozone, CFCs and nitrous oxide.
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What are wavelengths of UV, visible, and infrared?
UV - 100-400 nm, Visible - 380-780 nm - Infrared - 780 - 1 mil nm
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What can break bonds?
For each bond there is a photon, (light quanta) with enough energy to break it. E=hf where h = plank's constant.
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How is ozone made and destroyed?
O2 broken by UV with wavelength <240nm. Only occurs in stratosphere. Chapman cycle: O2 +UV -> 2O O+O2 -> O3 (making ozone) O3 +UV-> O+O2 O+O3 -> 2O2
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How is ozone maintained and what can change balance?
Ozone in stratosphere good, maintained due to balance of Chapman cycle. Ozone can increase from pollution in troposphere.
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What are chlorofluorocarbons?
chlorofluorocarbons (CFCs) have strong C-Cl and C-F bond strengths. Inert at Earth's surface, but broken down in atmosphere produce Cl
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How do CFCs destroy ozone?
UV hits CFC in atmosphere, makes chlorine atom break away. Chlorine atom collides with ozone, steals one oxygen and makes chlorine monoxide. When an oxygen atom hits, Cl is released and can then break down much more ozone
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What is smog?
Smog is enhanced by sunlight and temp inversions (LA weather) and is photochemical. Reactions from pollutants make ozone.
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How is ozone made by exhaust fumes? (Ozone harmful here)
N2 and O2 react at temps >1200 in combustion of car engines. N2+O2-> 2NO 2NO+O2 -> 2NO2 NO2 can dissipate to NO and O by low energy UV radiation. O combines with O2 to make ozone at troposphere, affects people, cyclic as NO and O3 make NO2 and O2
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What is acid rain and how is it made?
Acid rain has pH<4.5. Affects trees, aquatic life, public health. SO2 (from factories)and NOX (from car exhaust) react with water to make nitric and sulphuric acids.
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How does photochemical smog happen?
When NOX from exhaust combines with hydrocarbons from exhausts and high UV sunlight, reactions occur to make photochemical smog
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What are acid rain reactions?
NOX + H2O -> H2NO3 SO2 +H2O -> H2SO4
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How can sulphur and nitrogen affect people?
sulphur dioxide and NOX can return to troposphere harming health
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Other cards in this set

Card 2

Front

Why are the products of CO2 reactions equal in weight?

Back

In the CO2 reactions as charges are equal the mols/litre must be equal for equal overall charge

Card 3

Front

What is alkalinity and its formula?

Back

Preview of the front of card 3

Card 4

Front

Why is alkaline water important in nature?

Back

Preview of the front of card 4

Card 5

Front

How do stalagmites and stalactites occur?

Back

Preview of the front of card 5
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