ECHEM Chapter 9 – Flashcards
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| What happens to the mean free path at high altitudes? |
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| Becomes larger |
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| Describe the Troposhere |
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| 0 to 10 or 16 km top layer water freezes at -56C normal lapse rate |
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| Describe Stratosphere |
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| Troposphere to 50km Inverse lapse time Max [O3] ~10ppm Max temp -2c absorbs UV radiation |
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| Define normal lapse time |
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| temp decreases with increase in altitude |
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| Define inverse lapse time |
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temperature increases with increase in altitude observed in the stratosphere |
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| What is the relationship of increasing altitude and atmospheric pressure? |
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| Atmospheric pressure decreases logrithmicly |
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| Describe the mesosphere |
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| 50 to 85km normal lapse time lacks radiation absorbing species min temp -92C |
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| Describe Thermosphere |
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85 to ~500km temperature varied Max temp 1200C Absorption of highly energetic radiation(UV<100nm,x-ray,cosmic rays) |
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| Define Ionosphere |
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| 50km and up |
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| What is Earth's heating balance? |
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| 1.34x103 watts/m2 hits the thermosphere only half reaches Earth's surface |
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| Define mantle heating |
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| convection and conduction from Earth's mantle. equivalent to 1% of solar heating |
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| What are the three energy transport mechanisms? |
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| 1)Conduction 2)Convection 3)Radiation |
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| Define conduction |
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| Interaction of adjacent atoms |
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| Define convection |
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| movement of whole masses |
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| Define Radiation energy transport mechanism |
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Electromagnetic radiation E/M radiation only means of energy transport in vacuum.
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| What does the Earth have to do to all forms of energy in order to cool the planet? |
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| Convert it to electromagnetic radiation |
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| What is the average e/m energy that reaches the planet? |
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| ~500nm (Green Visible light) |
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| What is the average e/m energy given off by the planet? |
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| ~10,000 nm (Far IR) |
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| What is the green house effect approx equal to? |
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| [CO2] |
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| What happens to outgoing IR due to water vapor and CO2? |
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| It is absorbed and re-radiated with 1/2 going back to the planet resulting in a temp inc. |
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| What happens to UV-Vis and IR due to greenhouse gases? |
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| Transparent to uv-vis and absorbs IR. |
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| What is the chemical rxn for anaerobic respiration? |
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| 2{CH20}-;CH4 +CO2 |
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| What is the chemical rxn for aerobic respiration? |
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| {CH2O}+O2-;CO2+H2O |
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| What is the chemical reaction for photosynthesis? |
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| CO2+H2O+hv-;{CH2O}+H2O |
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| What is the chemical reaction for combustion? |
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C+O2-;CO2
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| What are the experimental parameters of a photochemical reaction? |
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| 1) Very low concentration of species 2) Very high pressure 3) High energy Radiation 4) No third bodies (No container walls) |
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| What are the seven relaxation mechanisms? |
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| 1) Physical quenching 2) Dissociation 3) Direct reaction 4) Luminescence 5) Intermolecular energy transfer 6) Intramolecular Transfer 7) Photoionization |
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| Define Physical quenching |
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Loss of energy to another molecule O2*+M-;O2+M(increased translational energy This process is followed by dissipation of energy as heat |
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| Define Dissociation |
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| Excite an electron in a bonding MO to a non bonding MO O2*->O+O |
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| Define Direct reaction |
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| Excite molecule reacts directly with another molecule O2*+O3-;2O2+O |
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| Define Luminesence |
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Excited species returns to ground state and gives of light NO2*-;NO2+hv The emitting wavelength is equal or lesser an energy than what cause the initial excitation |
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| Define Intermolecular energy transfer |
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Efficient energy transfer into a quantum state of another molecule(third body) which then becomes excited O2*+M-;O2+M* |
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| Define Intramolecular Transfer |
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| Transfer in which an excited species transfers energy with in the molecule X*Y->XY* |
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| Define Photoionization |
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Excited molecule ejects an electron, occurs in ionosphere(50km and up) N2*-;(N2+) + e- |
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| Where do ions exist in the atmosphere? |
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| In the upper atmosphere 50km and up |
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| What are the significant species found in the ionosphere? |
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| Cations and anions |
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| What is the most abundant anion in the ionosphere? |
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| electron |
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| Describe how SKIP occurs. |
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| Through photoionization, you get reflection of radiowaves if the particles formed are the same wavelength apart as the radiowave. During the day the ionosphere is made through photoionization and night it lifts. The reason for the lifting is because the particles are no longer being made and particles at lower elevation react more rapidly because of their shorter mean free path. |
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| What is the mean free path at sea level? |
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| 1x10-6 cm |
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| What is the mean free path at 500km |
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| 1x106 cm |
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| Describe the Santa Anna winds |
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| Electron rich winds that are formed by the friction of the winds stripping electrons from dried brush |
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| What is an example of Ions in the troposphere? |
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| Santa Anna Winds |
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| What are characteristics of free radicals? |
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| 1) Atoms with unpaired electrons 2) Formed by energetic radiation 3) highly reactive 4) Stable (relating to high mean free path) |
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| How would you compare excited atoms to free radicals? |
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| 1) Excited atoms have many ways to relax and don't require a collision 2) Free radicals are dependent on mean free path and have to react with a third body. (Life time increased with increase in mean free path) |
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| Define ozone: |
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| Molecule with a protective function of absorbing UV in the Stratosphere |
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| Where is good ozone found: |
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| Stratosphere |
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| Where is bad ozone found? |
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| Troposphere |
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| How is ozone produced? Two step process |
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1) O3+hv(242nm) -> O+O2 2)O+O2+M->O3+M(increased energy) |
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| Why is ozone depletion in the stratosphere a concern? |
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| Ozone production is very slow because of the long mean free path and the unlikelihood of O + O2 + a third body colliding simultaniously |
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| What are the negative effects of ozone in the troposphere? |
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1) Toxic, bind irreversibly to cytochrome c 2) Causes labored breathing and eye irritation 3) Oxidizing agent 4) damages materials |
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| Describe CO2 in the atmosphere |
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1) Minor constituent 0.035% or 350ppm 2) Like water vapor, CO2 absorbs IR 3) [CO2] rising ~1ppm/yr 4) Estimated increase in global temperature due to CO2 in 2050 is 1.5-4.5C |
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| What are seasonal trends of CO2? |
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| 1)Increased [C02] in fall/winter when photosynthesis is low and degredation is higher 2)Decreased [CO2] in summer when photosynthesis is at its peak. |
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| What is the phenomenon responsible for the temperature maximum at the boundary of the stratosphere and mesosphere? |
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| Due to the presence of O3 and the heating effect caused by the absorption of UV Followed by radiation and relaxation |
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| What function does a third body serve in an atmospheric chemical reaction? |
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| Third bodies absorb excess energy when the molecules form, stabilizing the newly formed molecule |
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| Why does the lower boundary of the ionosphere lift at night? |
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| In darkness, positive ions created by UV light recombine with free electrons in the lower regions of the ionosphere, the process is rapid at high molecular concentrations, causing the lower limit of the ionosphere to lift at night |
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| Considering the total number of electrons in NO2, why might it be expected that the reaction of a free radical with NO2 is a chain terminating reaction? |
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NO2 is chain terminating because, 1) NO2 is a stable free radical present at high concentrations and 2) the odd number of electrons make it chain terminating |
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| Of the species O, HO•*, NO2*, H3C•, and N+, which could most readily revert to a non reactive "normal" species in total isolation? |
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| NO2*, Excited species have a finite lifetime because they can lose energy through radiation w/o having to react with other species. |
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| What is the desinction between the symbols * and • in discussing chemically active species in the atmosphere? |
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| * means the molecule is in an excited electronic state • means free radical or molecular fragment with unshared electrons |
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| What two chemical species are most generally responsible for the removal of hydroxy radicals from the unpolluted troposphere? |
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| Methane and carbon monoxide |
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| Describe oxygen exchange among the atmosphere, geosphere, hydrosphere, and biosphere |
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1) oxygen consumed by reducing gases of volcanoes 2CO+O2->CO2 2)Oxygen consumed by burning of fossil fuels C+O2->CO2 3)Oxidative weathering of reduced minerals O2+4FeO->2Fe2O3 4)Respiration of plants and animals 5)Photosynthesis 6)Combined oxygen held in sediments Ca2+ +CO32-->CaCO3 7)Ozone shield absoption of UV radiation from 220-330nm 1)O3+hv->O+O2 2)O2+hv-> O+O 3)O+O2+M->O3+M(increased energy) |
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| How far does high energy wavelength (<100nm) penetrate? |
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| to approximately an altitude of 200km |
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| How far does UV radiation (200-300nm) penetrate? |
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| to approximately an altitude of 50km |
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| How far does radiation (wavelength > 330nm) penetrate? |
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| All the way through to the Earth's surface |
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| Composition of the atmosphere |
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| 78.08% nitrogen 20.95% oxygen 0.934% argon 0.035% CO2 0.005% Noble gases Varied water content 0.1% to 5.0% |
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| What ultimately happens to the energy absorbed as IR radiation? |
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| Dissipated as heat and raises the temperature of the whole atmosphere. |
