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32 Cards in this Set
- Front
- Back
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o Lakes (neutralizing agents)
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• Ca(OH)2(aq) + 2H+ → Ca2+ + 2H2O(aq) slaked lime (also could use NaOH(aq))
• NH4OH(aq) + H+ → NH4+ + H2O(aq) ammonium hydroxide |
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o Soil (buffer)
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• CaCO3(s) + 2H+ → Ca2+ + CO2(g) + H2O(aq) calcite or calcium carbonate
• Like eqn 5.7 |
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o Areas near the coast (buffer)
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• NaCl(s) + H+ → HCl(g) + Na+ natural sea spray
• Like eqn 5.5 |
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• What is the effect of acid deposition on marble and limestone buildings?
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o Gypsum (CaSO4-2H2O ) crust forms on calcite surface → over time rain removes crust and leaves pits → soot from smoke deposits into pits and darkens buildings
H2SO4(aq) → 2H+ + SO42- CaCO3(s) + 2H+ → Ca2+ + CO2 + H2O(aq) Ca2+ + SO42- + 2H2O(aq) → CaSO4-2H2O(s) H2SO4(aq) + CaCO3(s) + H2O(aq) → CaSO4-2H2O(s) + CO2(g) overall process |
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• Explain the latitudinal and vertical distribution of ozone.
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o Latitudinal (see Fig. 11.3): dip in the equator (0 deg) is due to warm air rising, which brings up ozone-poor air. Ozone-rich air gets pushed to the poles. Maximum in south at 60 degrees latitude b/c of polar vortex (air sinks in front of this barrier). The ozone hole in the Antarctic and the ozone dent in the Arctic are due to PSCs.
o Vertical (see Fig. 11.4): concentration of ozone is a function of the short wavelengths (which are required to photolyze molecular oxygen) and the amount of oxygen available (which decreases with increasing altitude) • O3 number concentration peaks around 25 km, but O3 mixing ratio peaks around 30 km • O3 concentration also peaks at surface, but O3 mixing ratio is small b/c air concentration peaks at surface |
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• What does the ozone layer do to protect life on earth?
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o Absorbs short wavelength UV rays (shorter than 0.35 um, absorbing all UV-C and some UV-B)
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• How is ozone naturally produced and destroyed (non-catalytic cycles) in the stratosphere (show reactions)?
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o Stratosphere: Chapman Cycle (all gas phase)
• Formation (eqn 11.2, 11.4) • O2+hv→O+O(175to245nn) **FarUV • O + O2 + M→O3 +M • Destruction (eqn 11.6-11.8) • O3 +hv→O2 + O (> 310 nm) **Near UV • O +O3→2O2 • O + O +M→O2 |
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• How is ozone naturally produced and destroyed in the troposphere?
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o Troposphere: (all gas phase)
• Formation (2 of the 3 photostationary state eqn’s) • NO2 + hv→NO + O • O + O2 + M→O3 +M • Destruction (eqn 11.5-11.6) • O3 +hv→O2 + O(‘D) (< 310 nm) • O3 +hv→O2 + O (> 310 nm) |
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difference between troposphere and stratosphere ozone
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• Tropospheric O3 from photolysis of NO2, stratospheric O3 from photolysis of O2 – short wavelengths (far UV) are filtered out by O2 in stratosphere, so don’t have the short wavelengths in the troposphere to photolyze O2 (photolyze NO2 instead b/c it requires longer wavelengths)
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o NOx (NO and NO2) catalytic ozone destruction cycle (eqn 11.10 – 11.12): (all gas phase)
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• First, get NO from: N2O + O(‘D)→NO + NO
• Then: NO +O3→NO2 + O2 • NO2 + O→NO + O2 • O + O3→2O2 NET PROCESS o NOx removal (slow time scale): (all gas phase) • NO2 +OH +M→HNO3 + M • HO2 +NO2 +M→HO2NO2 + M |
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o HOx (OH and HO2) catalytic ozone destruction cycle (eqn 11.16-11.18): (all gas phase)
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• First, get OH from one of several rxns: O(‘D) + { H2O, CH4, H2}→OH + { OH, CH3, H}
• Then: OH + O3→HO2 + O2 • HO2 + O3→OH + 2O2 • 2O3→3O2 NET PROCESS o HOx removal: (all gas phase) • HOx removed by same rxn’s as NOx, plus (slow time scale): • HO2 + OH→H2O + O2 |
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• Define chain length. How does it differ for the above two catalytic ozone destruction cycles?
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o Chain length = number of times cycle is executed before specie causing O3 loss (NOx and HOx in the above two cases) is removed from the cycle by reaction with another gas
o NOx catalytic ozone destruction cycle: • CL = 10^5 in upper stratosphere→10^5 molecules of O3 are destroyed before one NOx molecule is removed from the cycle • CL = 10 in the lower stratosphere o HOx catalytic ozone destruction cycle: • CL = 1 – 40 in lower stratosphere |
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• What are CFCs (general chemical composition)? Why are they important to stratospheric ozone destruction?
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o gases synthetically produced by replacing all H atoms in methane(CH4) or ethane (C2H6) with Cl and/or F atoms – nontoxic, nonflammable, inexpensive, long lifetimes (very stable) and non- soluble (so can move up to stratosphere) – used as spray can propellants, coolants, air conditioning systems
o invented by Thomas Midgley o Destroy stratospheric ozone |
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• What time of year do the ozone hole and ozone dent occur, respectively? Where is each located?
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o Ozone hole – Antarctic – Southern Hemisphere spring (Sept – November)
o Ozone dent – Arctic – Northern Hemisphere late winter and spring (March – May) |
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• What are the most important chlorine reservoirs and active chlorine species?
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o Reservoirs: ClONO2, HCl
o Active: ClO, Cl |
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• Describe the global-scale chlorine catalytic destruction mechanism for ozone.
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o See equations 11.23 – 11.25.
o Cl + O3→ClO + O2 o ClO + O→Cl + O2 o O + O3→2O2 NET PROCESS • Lower stratosphere: CL=10 • Middle and upper stratosphere: CL=1000 o This destruction mechanism is not important in the ozone hole formation because it is not the same cycle that causes nearly all of the ozone hole (this global cycle only accounts for 2-3% of ozone destruction). |
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What mechanism is most important for ozone destruction over the Antarctic, and why?
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o Dimer Mechanism (Polar stratospheric catalytic ozone destruction cycle):
• 2 x [Cl(g) + O3(g)→ClO(g) + O2(g)] • ClO(g) + ClO(g) +M→Cl2O2(g) + M • Cl2O2(g) + hv→ClOO(g) + Cl(g) <360nm • ClOO(g) + M→Cl(g) + O2(g) +M • 2O3(g)→3O2(g) NET PROCESS • [ClO] is not significant enough on global scale for this mechanism to be important, since rate = k*[ClO]^2 |
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• What is essential for freeing up chlorine from chlorine reservoirs that allows the ozone hole to happen? Why?
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o Surfaces for reactions to convert reservoir chlorine to more active chlorine – In the poles, PSC’s serve this purpose. PSCs require very cold temperatures therefore form only at the poles during winter. Heterogeneous reactions (called “chlorine activation”) take place on the surface of PSCs (require a gas to be adsorbed to the surface) that convert inactive forms such as HCl and ClONO2 to photochemically active forms (Cl2, HOCl, ClNO2):
• Most important chlorine activation rxn: ClONO2(g) + HCl(a)→Cl2(g) + HNO3(a) o These photochemically active forms are photolyzed in early spring (when the sun comes back out) to ClO and Cl (active species), which destroy ozone primarily through the Dimer Mechanim (above). • Cl2(g) + hv→2Cl(g) <450 nm |
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• Summarize the key steps in the formation of the Antarctic ozone hole.
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o 1. The Antarctic winter is dark and cold.
o 2. A circumpolar vortex forms around the region, trapping cold air in the region. o 3. When temperatures drop sufficiently, Polar Stratospheric Cloud (PSC) crystals form. o 4. Chemical reactions on the surfaces of these crystals convert reservoirs of chlorine [HCl(g), ClONO2(g)] to other forms of chlorine [Cl2(g), HOCl(g), ClNO2(g)]. o 5. In springtime, when the sun appears, sunlight breaks down Cl2(g), HOCl(g), ClNO2(g) into Cl(g)and ClO(g). These gases catalytically destroy ozone (primarily with Dimer Mechanism). o 6. As temperatures warm up, PSCs melt and evaporate, the polar vortex breaks down, ozoneregenerates chemically, and outside ozone transports back into the polar region. |
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• Describe the natural greenhouse effect. How much does it raise the temperature on earth?
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o 33K→compare incoming solar radiation (energy absorbed by Earth, Ein, eqn 12.4) to outgoing thermal-IR radiation (energy radiated from Earth, Eout, eqn 12.5):
o Ein = Fs*(1-Ae)*(pi*Re2) o Eout = εeσBTe4 *(4*pi*Re2) • With no GH effect at all (that is, no atmosphere), Ein must equal Eout, which gives the equation for the equilibrium temperature (Te, eqn 12.6): Te = [Fs*(1-Ae) / (4εeσB)] 1⁄4 • The corresponding Te is 255K (this is too cold to support life - see example 12.1), which is 33K cooler than the actual 288K surface temperature, meaning that the presence of an atmosphere raises the temperature on earth b 33K o This 33K warming by the atmosphere (natural background GHGs) is the natural GH effect, where the atmosphere selectively absorbs a portion of the outgoing thermal-IR radiation (Eout), and some of this absorbed radiation is reemitted back to Earth, warming the surface o Global warming is an increase in Earth’s temperature above the natural GH effect due to emissions of GHGs and black carbon – absorb more of Eout and reemit back to Earth |
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• What is the largest contributor (and second largest contributor) to global warming? What are the most important sources today? (see Figure 12.3, last column to right)
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o Largest: CO2 – fossil fuels & biomass burning, deforestation
o Second largest: BC (not CH4) – fossil fuel & biomass burning (coal, diesel fuel, jet fuel, n. gas, kerosene) o *Note: there are other gases more efficient (molecule for molecule) at absorbing thermal-IR radiation, so these gases are a concern (i.e. CH4, N2O) |
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• Why is the troposphere warming and the stratosphere cooling? What does this mean for the ozone layer? (see section 12.5.5)
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o Troposphere is warming b/c GHGs are absorbing and reemitting more outgoing IR radiation (Eout) that would have otherwise escaped to the stratosphere – as a result, the stratosphere is cooling b/c it’s receiving less IR radiation from the Earth (where is would have been absorbed by ozone and natural GHGs)
o Cooler stratosphere enhances the formation rate of PSCs and increases the relative humidity (causes aerosol particles to grow in size), both of which lead to higher surface areas (and for longer periods of time), increasing the conversion of chlorine reservoirs to active forms of chlorine, which destroy stratospheric ozone - even though chlorine levels are decreasing, the rates of ozone loss due to existing chlorine is increasing, slowing the recovery of the ozone hole |
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o Eccentricity
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• 100,000 year cycle
• Is change in shape of Earth’s orbit around the sun→higher e is more elliptical shape(lower T b/c Earth further away from sun), lower e is more circular (higher temp b/c Earth closer to sun) • Change global temp, responsible for last 4 glacial periods over the past 450,000 years (changes CO2 were a response to changes in temperature induced by changes in eccentricity – today, CO2 changes are driving changes in temp) |
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o Obliquity
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• 41,000 year cycle
• Tilt angle of Earth (axis of rotation) • Change seasons: low obliquity = more sun to equator and less to poles (high variation in seasons), high obliquity = more sun to poles and less to equation (less variation in seasons) |
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o Precession
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• 22,000 year cycle
• Wobble of Earth • Change seasons: how close each hemisphere is to sun in winter and summer (if reverse wobble from current status, then NH summer will occur when Earth is closer to the sun,resulting in warmer summer) |
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• What effect do aerosols have on the climate (section 12.4.3)?
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temp:cooling
rain: less rain o Temperature: • Reflective aerosols reflect sunlight back to space, cooling the ground – increase albedo (water, nitrate, sulfate, organic compounds) • Absorbing aerosols (like soot, BC) absorb the sunlight, heating themselves up and radiating the heat to the air around them – but the ground cools b/c sunlight hitting ground is reduced (although warming of the air can warm the ground some) • Increased # of aerosol particles means that there is an increased # of CCN, so get more and smaller cloud drops, which results in a higher reflectivity, cooling the ground o Precipitation : • Having a smaller-sized cloud drops (from increase # of CCN) delays the formation of raindrops, which reduced precipitation • Having warm air over cool ground (from absorptive aerosols) increases stability of air, which reduces convection (vertical movement of air), which reduced precipitation |
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o Water-vapor-temperature-rise
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positive
• Higher temperatures→more evaporation of water from ocean→since water vapor is a GHG, it causes the temperature to further increase |
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o Snow-albedo
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positive
• Higher temperatures→snow melts→lower albedo, so get more absorption of solar radiation, which causes temperatures to further increase |
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o Water-vapor-high-cloud (ice clouds)
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positive
• Higher temperatures→more evaporation of water from oceans which increases the cover of high clouds made of ice (transparent to solar UV radiation but absorbent of thermal-IR radiation)→more absorption and reeimission of Earth’s thermal-IR radiation which increases temperatures further |
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o Water-vapor-low-cloud (liquid water clouds)
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negative
• Higher temperatures→more evaporation of water from oceans which increases the cover of low clouds (reflect incoming solar UV radiation)→more reflection increases the albedo and reduces the amount of incident solar UV radiation, causing temperatures to decrease |
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o Plant-carbon-dioxide
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negative
• Higher temperatures→plants and trees flourish and photosynthesize more→quantity of CO2 decreases which decreases temperatures |
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• Name 5 impacts of global warming
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o Rise in sea levels
o Changes in regional climate o Changes in agriculture o Changes in ecosystems o More stratospheric ozone destruction o More heat stress and heat-related health problems |
