ENV final
Of the following, the one that is not an inorganic pollutant gas is (explain): (A) Benzo(a)pyrene, (B) SO2, (C) NO, (D) NO2, (E) H2S.
(A) Benzo(a)pyrene is a carbon-rich hydrocarbon
Match the following pertaining to classes of atmospheric chemical species: (A)NO2 (1) Reductant (B) H2S (2) Corrosive substance (C) NH4HSO4 (3) Photochemically active species (D)O2* (4) Of the species shown, most likely to dissociate without additional outside input
(A)-(3), (B)-(1), (C)-(2), (D)-(4)
Match the following pertaining to gaseous inorganic air pollutants: (A) CO, (B) O3, (C) SO2, (D) NO (1) Produced in internal combustion engines as a precursor to photochemical smog formation (2) Formed in connection with photochemical smog (3) Not associated particularly with smog or acid rain formation, but of concern because of its direct toxic effects (4) Does not cause smog to form, but is a precursor to acid rain.
(A)-(3), (B)-(2), (C)-(4), (D)-(1)
Of the following, the species that is least likely to be a constituent of solid or liquid atmospheric particulate matter is (explain): (A) C, (B) O3 (C) H2SO4, (D) NaCl, (E) benzo(a)pyrene.
(B) O3 would not be in particles because it is a gas.
Of the following, the statement that is untrue regarding particles in the atmosphere is (explain): (A) Dispersion aerosol particles formed by grinding up bulk matter are typically relatively large, (B) very small particles tend to be acidic and often originate from gases, (C) Al, Fe, Ca, and Si in particles often come from soil erosion, (D)carcinogenic polycyclic aromatic hydrocarbons may be synthesized from saturated hydrocarbons under oxygen-deficient conditions, (E) larger particles are more harmful because they contain more matter.
E) is untrue, larger particles are relatively less harmful because they are less respirable and damaging to the lungs.
Of the following, the most likely to be formed by pyrosynthesis is (explain): (A) Sulfate particles, (B) Ammonium particles, (C) sulfuric acid mist, (D) PAHs, (E) ozone in smog.
D) PAHs,
Of the following the true statement is (A) incoming solar energy is primarily in the form of infrared radiation, (B) The very cold tropopause layer at the top of the troposphere is the major absorber of harmful ultraviolet radiation from the sun, (C) The stratosphere is defined as a region of the atmosphere in which temperature decreases with increasing altitude, (D) a large fraction of solar energy is converted to latent heat by evaporation of water to produce water vapor in the atmosphere, (E) temperature inversions are most useful because they cause air pollutants to disperse.
D) a large fraction of solar energy is converted to latent heat by evaporation of water to produce water vapor in the atmosphere,
Of the following, the statement that is not true regarding carbon monoxide in the atmosphere is (explain): (A) It is produced in the stratosphere by a process that starts with H abstraction from CH4 by HO•, (B) it is removed from the atmosphere largely by reaction with hydroxyl radical, (C) it is removed from the atmosphere in part by its being metabolized by soil microorganisms, (D) it has some natural, as well as pollutant, sources, (E) at its average concentration in the global atmosphere, it is probably a threat to human health.
E) Carbon monoxide is a health hazard only in localized areas of high concentration
Free radicals do not or are not (A) have unpaired electrons, (B) normally highly reactive, (C) last longer in the stratosphere than in the troposphere, (D) take part in chain reactions, (E) lose their energy spontaneously, reverting to a stable species by themselves.
E) lose their energy spontaneously, reverting to a stable species by themselves.
What is the main species responsible for the oxidation of NO to NO2 in a smoggy atmosphere?
Organic peroxy radicals, ROO•, oxidize NO to NO2 in a smoggy atmosphere
Why is ozone especially damaging to rubber?
Ozone is especially damaging to rubber because of its strong tendency to add across double bonds in the rubber polymer causing the rubber to become brittle.
At what point in the smog-producing chain reaction is PAN formed?
PAN is generated as the result of several chain reactions near the end of the smog forming process.
What is the most stable type of hydrocarbon that has a very low hydrogen-to-carbon ratio?
Polycyclic aromatic hydrocarbons such as benzo(a)pyrene
12. Of the following species, the one most likely to be found in reducing smog is: ozone, relatively high levels of atomic oxygen, SO2, PAN, PBN.
SO2
What type of process results in the formation of very small aerosol particles?
Very small particles tend to be condensation aerosols formed by reactions of gases.
What pollution problem does a lean mixture aggravate when employed to control hydrocarbon emissions from an internal combustion engine?
A lean mixture tends to produce more nitrogen oxides.
What is the distinction between reactivity and instability as applied to some of the chemically active species in a smog-forming atmosphere?
A reactive species has a strong tendency to react but, in the absence of some species with which to react, it might be relatively stable. An unstable species is one that tends to gain stability by undergoing some sort of process on its own. Sulfur dioxide, SO2, is stable for some time in the atmosphere in the absence of oxidants such as those present in photochemical smog in which case it undergoes rapid oxidation. Excited nitrogen dioxide, NO2*, is unstable and readily emits a photon to revert to ground-state NO2.
Of the following, the one that is not a characteristic of dispersion aerosols is (explain): (A) They are most readily carried into the alveoli of lungs, (B) they are usually above 1 µm in size, (C) they are relatively easier to remove, (D) they are generally less respirable, (E) they are produced when bulk materials (larger particles) are ground up or sub divided.
A), dispersion aerosols tend to be relatively large and not carried readily into the lungs.
Match the constituent of particulate matter from the left with its most likely source from the right, below: (A) Si (1) Natural sources, soil erosion (B) PAH (2) Incomplete combustion of hydrocarbons (C) SO32-(3). Element largely introduced by human activities (D) Pb (4) Reaction of a gas in the atmosphere
A)-(1), (B)-(2), (C)-(4), (D)-(3)
Match each particle constituent below, left, with its likely source: (A) Si (1) From gases in the surrounding atmosphere (B) V (2) From natural sources (C) Benzo(a)pyrene (3) Combustion of certain kinds of fuel oil (D) Sulfuric acid droplets (4) From incomplete combustion
A)-2, (B)-3, (C)-4, (D)-1
When reacting with hydroxyl radical, alkenes have a reaction mechanism not available to alkanes, which makes the alkenes much more reactive. What is this mechanism?
Alkenes can undergo addition reactions, which are particularly rapid with hydroxyl radical.
Why are automotive exhaust pollutant hydrocarbons even more damaging to the environment than their quantities would indicate?
Automotive exhaust pollutant hydrocarbons contain a relatively high proportion of unsaturated alkenes, which readily react in the atmosphere to produce photochemical smog.
Of the following the true statement is (A) chemiluminescence refers to a chemical reaction that results from a molecule having absorbed a photon of light, (B) O* denotes an excited oxygen atom, (C) O2* denotes a free radical, (D) HO• is an insignificant species in the atmosphere, (E) the longer the wavelength of incoming solar radiation, the more likely it is to cause a photochemical reaction to occur.
B) O* denotes an excited oxygen atom,
11. hy are hydrocarbon emissions from uncontrolled automobile exhaust particularly reactive?
Because they have a high concentration of reactive alkenes
What two chemical species are most generally responsible for the removal of hydroxyl radical from the unpolluted troposphere?
Both CH4 and CO react readily with hydroxyl radical resulting in its removal from the atmosphere.
10. Why is it that "highest levels of carbon monoxide tend to occur in congested urban areas at times when the maximum number of people are exposed?"
Carbon monoxide comes primarily from automobile exhausts and levels are especially high in areas of heavy traffic such as busy intersections.
Earth's atmosphere is stratified into layers. Of the following, the true statement regarding this stratification, the characteristics of the layers, and the characteristics of species in the layers is (A) the stratosphere and troposphere have essentially the same composition, (B) the upper boundary of the stratosphere is colder than the upper boundary of the troposphere because the former is higher, (C) ozone is most desirable near Earth's surface in the troposphere, (D) the composition of the troposphere is characterized by both its high and uniform content of water vapor, (E) the boundary between the troposphere and the stratosphere serves as a barrier to the movement of one of the important constituents of tropospheric air.
E) the boundary between the troposphere and the stratosphere serves as a barrier to the movement of one of the important constituents of tropospheric air.
What two vapor forms of mercury might be found in the atmosphere?
Elemental mercury and dimethyl mercury
What function does a third body serve in an atmospheric chemical reaction?
It absorbs excess energy from an energetic newly formed or excited molecule or radical preventing it from dissociating
Why is a modern automotive catalytic converter called a "three-way conversion catalyst?"
It is called a three-way conversion catalyst because a single catalytic unit destroys all three of the main classes of automobile exhaust pollutants — hydrocarbons, carbon monoxide, and nitrogen oxides.
In what major respect is NO2 a more significant species than SO2 in terms of participation in atmospheric chemical reactions?
NO2 can undergo photochemical dissociation to yield reactive O atoms that start atmospheric chain reactions
Of the species O, HO*•, NO2*, H3C•, and N+, which could most readily revert to a nonreactive, "normal" species in total isolation?
NO2* because it is an excited state of the NO2 molecule and could revert to the stable ground state by emitting a photon. Each of the other species would have to react with something else to become a stable species which could not happen in total isolation.
Of the gases neon, sulfur dioxide, helium, oxygen, and nitrogen, which shows the most variation in its atmospheric concentration?
Sulfur dioxide because it is emitted to the atmosphere as a pollutant and undergoes atmospheric reactions, such as formation of H2SO4, that remove it from the atmosphere
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?
The NO2 molecule has an uneven number of electrons meaning that one of its valence electrons is unpaired and available to form a bond with the unpaired electron in a radical to produce a stable species.
8. What phenomenon is responsible for the temperature maximum at the boundary of the stratosphere and the mesosphere?
The absorption of energy from ultraviolet radiation, primarily O2 and O3, warms this region.
Assume an accidental release of a mixture of gaseous alkanes and alkenes into an urban atmosphere early in the morning. Assume that the mass of air is subjected to intense sunlight during the day and is kept in a stagnant condition by a thermal inversion. If the atmosphere at the release site is monitored for these compounds, what can be said about their total and relative concentrations at the end of the day? Explain.
The conditions described are those in which photochemical smog forms. The concentrations of both kinds of hydrocarbons should decrease during the day as they undergo reactions with O atoms, HO• radicals, and O3. The concentrations of the more reactive alkenes would decrease faster than those of the alkanes and the ratio of alkanes to alkenes would increase during the day.
Which unstable, reactive species is responsible for the removal of CO from the atmosphere?
The hydroxyl radical, HO•, reacts rapidly with CO resulting in its oxidation to CO2.
Each of the following occurs during smog formation. Place each in order from the one that occurs first (denoted 1) to the one that occurs last (denoted 5) and explain your choice: (A) An alkyl peroxyl radical, ROO•, is produced, (B) particles in the atmosphere obscure visibility, (C) NO and another product are produced from NO2, (D) NO reacts to produce NO2, (E) an alkyl radical, R•, is produced from a hydrocarbon.
The order would be 1-C, 2-E, 3-A, 4-D, 5-B. The process is initiated by the photochemical dissociation of NO2 to produce O atoms. The O atoms extract H from hydrocarbons to yield alkyl radicals, R•, which in turn add O2 to produce peroxyl radicals, ROO•. NO2 is regenerated by the oxidation of NO by ROO•. The last step in the process is the generation of particles as the final products of the photochemical oxidation of organics in the atmosphere.
Per unit mass, why are smaller particles relatively more effective catalysts for atmospheric chemical reactions?
The smaller particles are relatively much more numerous and have greater total surface areas on which reactions may be catalyzed.
It may be argued that wind energy, which is now used by growing numbers of large turbines to generate renewable electricity, is actually a form of solar energy. Explain on the basis of meteorological phenomena the rationale for this argument.
The sun heats masses of air causing expansion, which is manifested by wind blowing.
What is the distinction between the symbols * and • in discussing chemically active species in the atmosphere?
The symbol * denotes an excited state and • denotes a free radical with an unpaired electron
9. A freight train that included a tank car containing anhydrous NH3 and one containing concentrated HCl was wrecked, causing both of the tank cars to leak. In the region between the cars a white aerosol formed. What was it, and how was it produced?
The white aerosol was solid NH4Cl formed by the reaction: NH3(g) + HCl(g) → NH4Cl(s)
Why are aerosols in the 0.1-1 µm size range especially effective in scattering light?
These particles are of about the same dimensions as the wavelengths of visible light which makes them especially effective in scattering light.
