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Practice Final – December, 2006

Practice Final – December, 2006. 1.      The oxidation state of sulfur (S) in SO 4 2- is: (a) +6 (b) +4 (c) +2 (d) 0 (a) +6 (b) +4 (c) +2 (d) 0  

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Practice Final – December, 2006

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  1. Practice Final – December, 2006

  2. 1.      The oxidation state of sulfur (S) in SO42- is: • (a) +6 (b) +4 (c) +2 (d) 0 • (a) +6 (b) +4 (c) +2 (d) 0   • 2. If there is no disinfectant in the distribution system of the drinking water supply, recontamination can occur due to: • (a)    low pressure at the outer edges of the distribution system, allowing contamination from the ground. • b) formation of chloroform and other chlorinated compounds • (c) loss of ozone in the distribution system • (d) none of the above • (a)    low pressure at the outer edges of the distribution system, allowing contamination from the ground.

  3. 3. When using incineration to reduce waste, one of the disadvantages is • (a) impossible to recover trace metals from the fly ash • (b) inability to recover waste heat • (c) formation of polychorinated dibenzo-p-dioxins and dibenzofurans • (d) low efficiency in the destruction of hazardous materials • (c) formation of polychorinated dibenzo-p-dioxins and dibenzofurans • 4. Chlorinated solvents are the subject of environmental concern because of • (a) their ozone depletion potential • (b) their potential to chelate other compounds • (c) their potential to form other compounds • (d) none of the above • (a) their ozone depletion potential

  4. 5. When considering the toxicity of trace metals the most important factor effecting the the metal's toxicity is its: • (a) speciation (b) absorption spectrum (c) atomic weight (d) density • (a) speciation • 6. Which of the following statements is true regarding methymercury in fish. • (a) Methylmercury in fish is found only in the digestive tract. • (b) Fish cannot bioaccumlate mercury. • (c) Highest concentrations found in long-lived predatory fish. • (d) once the fish has consumed the methymercury, there is no process for elimination. • (c) Highest concentrations found in long-lived predatory fish

  5. 7. Most of the mercury present in humans is in the form of • (a) Hgo (b) Hg22+ (c) Hg2+ (d) methylmercury • (d) methylmercury • 8-12. Given the dissociation constant for acetic acid; 1.8 x10-5. (a) Calculate the pH for a 0.04 M solution of acetic acid, HOAc. • HOAc  H+ + Oac- Ka = 1.8x10-5 •    0.04 - - •   0.04-x x x • [x][x]/0.04 = 1.8x10-5 • [x]2 = 7.2 x10-7 [x] = 8.48x10-4 pH = 3.07

  6. (b) What would be the pH if 0.01 M NaOAc were added to the solution. • HOAc  H+ + OAc- Ka = 1.8x10-5 • 0.04 - 0.01 • 0.04-x x 0.01 + x • [x][0.01]/[0.04] = 1.8 x 10-5 •   x = 7.2 x 10-5 •   pH = 4.14

  7.  13.  The two figures show the dose-response curves for exposure of two organisms to a specific toxicant. • (a)    both curves have the same EC50 values • (b)   both organisms have the same LOEC (lowest observed effective conc.) • (c)    there is no correlation between the two graphs • (d)   all the organisms have the same susceptibility to the chemical toxicant •   (a)    both curves have the same EC50 values

  8. 14. Which of the following statements is not true? • (a) underlying limestone rocks can provide a buffering system to mitigate the effects of acid rain. • (b) in early spring there is often an influx of the winter's accumulation of acid snow. • (c) trees at high altitudes are least affected by acid rain due to protection of low-lying clouds. • (d) "sulfation" is the replacement of CaCO3 by CaSO4 on historical monuments. • (c) trees at high altitudes are least affected by acid rain due to protection of low-lying clouds. • 15-17. Given KH(Henry's law constant) = 3.38x10-2 moles L-1 atm-1 and Ka1 = 4.45x10-7 for carbonic acid (H2CO3), calculate the pH of water in equilibrium with CO2 in the atmosphere where the concentration of [CO2] = 316 ppm. • [H2CO3] = 3.16x10-4 x 3.38 x10-2 •   [H2CO3] = 1.06 x 10-5 •    H2CO3  H+ + HCO3-1 • 1.06x10-5 -x x x • [x}{x] = 4.7x10-12 [x] = 2.1x10-6 pH = 5.68

  9. 18. Which one of the following ions is responsible for making water "hard"? • a. Na+ b. Mg2+ c. SO42- d. CO32- • b. Mg2+

  10. 21. The difference between the effect of DDT and DDE on the calcification of eggshells is due to • (a) number of chlorine atoms (b) structure • (c) chemical reactivity (d) lipophilicity • (b) structure • 22. The octanol-water partition coefficient measures • (a)    ease of reduction (b) half-life • (c) chlorine/hydrogen ratio (d) degree of lipophilicity • (d) degree of lipophilicity • When studying the eggs of migratory birds for DDT and DDE a high ratio of DDT to DDE means • (a)    the birds have encountered a place where DDT is still likely being used • (b)   the egg shells will be too thin to allow hatching • (c)    organophosphorus pesticides are replacing the chlorinated pesticides • (d)   the migratory birds will tend to not migrate any longer •   (a)    the birds have encountered a place where DDT is still likely being used

  11. 24. When considering the environmental fate of a molecule, one must consider • (a) temperature (b) pH of the environment (c) microorganisms (d) all of these • (d) all of these • 25.  The figure on the left shows the H2CO3, HCO3-, CO32- fractions in natural water as functions of pH. • The line B represents: • (a) H2CO3 (b) HCO3- • (c) CO32- (d) H2O  • b) HCO3-

  12. PCBs • (a)    can form dioxins when heated • (b)   have been shown to cause IQ deficiency when content in blood is high • (c)    have the same toxicity, regardless of the congener • (d)   are disposed of by electrolysis • b)   have been shown to cause IQ deficiency when content in blood is high • Petroleum Aromatic Hydrocarbons (PAHs) are • (a)    pollutants associated with incomplete combustion • (b)   are volatile organic hydrocarbons • (c)    known to react with air to form furans • (d)   none of these •   (a)    pollutants associated with incomplete combustion • 28. Dissolved oxygen in water can be effected by • (a) decomposition of biomass (b) thermal pollution • (c) sewage (d) all of these • (d) all of these

  13. 29. CH3Hg+ and (CH3)2Hg are • (a) both present in the atmosphere as gaeous molecules. • (b) both lipid soluble (and hence bioconcentrate) • (c) both kinetically reactive, and thus very unstable. • (d) all of the above. • (b) both lipid soluble (and hence bioconcentrate) • 30. The principal risk to children from lead is • (a) skin cancer (b) damage to the retina • (c) “blue baby” syndrome (d) interference with development of the brain. • (d) interference with development of the brain.

  14. Questions 31-33 relate to this figure which shows the biological response of organisms to toxicant concentrations • Region C represents • (a)    no toxic effect (b) irreversible effects • (b)   death (d) none of these • (b) irreversible effects • A micronutrient, e.g. copper, is represented by • (a) curve 1 (b) curve 2 • (c) curves 1 and 2 (d) neither curve 1 or 2 • (a) curve 1 • Acute toxicity testing occurs in • (a) Region A (b) Region B (c) Region C (d) Region D •  (d) Region D

  15.  34. In the use of hypochlorous acid, HOCl as a disinfectant, the pH is maintained around 7.5 to: • (a) increase the solubility of Cl2 gas • (b) prevent the ionization of HOCl to hypochlorite ion, OCl- • HOCl(aq) <-------> H+(aq) + OCl- aq) • (c) make the water taste better. • (d) keep phosphates from precipitating out. • (b) prevent the ionization of HOCl to hypochlorite ion, OCl- • HOCl(aq) <-------> H+(aq) + OCl- aq) • 35.  Which of the following is not a disinfectant in the treatment of drinking water • (a) ClO2 (b) H2O2 (c) UV light (d) O3 • (b) H2O2 • . 36. Which of the following compounds is axenobiotic substance? • (a) N2O (b) CO2 (c) CHCl3 (d) O3 • (c) CHCl3

  16. 37. The trace greenhouse gases: methane, nitrous oxide, and CFCs will likely have a combined effect comparable to CO2 because of • (a) their absolute levels of emission • (b) their efficiency of radiation trapping • (c) their atmospheric lifetime • (d) all of these. • (d) all of these • 38. Which of the following species absorbs infrared radiation in the troposphere? • a. N2 b. O2 c. CO2 d. Ar • c. CO2

  17. 40. Which of the following reactions is representative of hydroxyl free radical chemistry? • (a) CHCl3 + OH ---------> CHCl2OH + Cl • (b) CHCl3 + OH ----------> CHCl2 + HCl • (c) OH(g) + NO2(g)-------M-----> HNO3(g) • (d) CHCl3 + OH -----------> CH2OCl + Cl2 • (c) OH(g) + NO2(g)-------M-----> HNO3(g) • 41. Which of the following reactions is not necessary in the major route for the formation of the hydroxyl radical in the troposphere? • (a) NO2 ----hn,l < 400 nm----> NO + O • (b) O2 + NO2 -----------------> NO + O3 • (c) O3 -------hn,l < 320 nm---> O2* + O* • (d) O* + H2O ----------> 2 OH (where O* is an excited oxygen atom) • (b) O2 + NO2 -----------------> NO + O3

  18. 42. The most common fate of peroxy radicals in tropospheric air, except of the very cleanest of air as that over the ocean, is illustrated in which of the following reactions: • (a) HSO3 + NO --------> NO2 + HSO2 • (b) H2O2 -----------> H2 + O2 • (c) CH3COO + OH ----------> CH3COH + O2 • (d) HSO2 + OH --------> H2SO3 • (a) HSO3 + NO --------> NO2 + HSO2 • 43. Which of the following reactions takes place in a catalytic converter • (a) OH + SO2 --------> HSO3 • (b) CO2 + 1/2 N2 -------> CO + NO • (c) H2 + NOx ---------> N2 + H2O • (d) 1/2 O2 + NO ----------> NO2 • (c) H2 + NOx ---------> N2 + H2O

  19. 45-50. Given the following equilibria constants • H2CO3 -----> H+ + HCO3- Ka1 = 4.5 x 10-7 • HCO3- ------> H+ + CO32- Ka2 = 4.7 x 10-11 • CaCO3 ------> Ca2+ + CO32- Ksp = 4.6 x 10-9 • calculate the equilibrium constant for the reaction • HCO3- + H2O --------> H2CO3 + OH- • K = [H2CO3][OH-]/[HCO3-] = [H2CO3][OH-][H+] /[HCO3-][H+] • K = Kw/Ka1 = 1x10-14/4.5x10-7 = 2.2x10-8

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