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ampere atmosphere atomic mass unit atomic molar mass Avogadro constant Celsius temperature centi- prefix coulomb electromotive force energy of activation enthalpy entropy equilibrium constant ABBREVIATIONS AND SYMBOLS F molal A Faraday constant M molar atm formula molar mass u free energy G molar mass A frequency v mole R Planck's constant 7VA gas constant g pressure °C gram C p rate constant c heat capacity h retention factor C hour J second E joule Ea kelvin K temperature, K k time H kilo- prefix liter L volt S milli— prefix m K CONSTANTS m M M mol h P k Rf s T / V # = 8.314 J-mol '-K l tf = 0.0821 L-atm-mol'-K > 1 F= 96,500 C-mol 1 1 F= 96,500 J - V ' - m o l 1 7VA = 6.022 x l O 2 3 mol ] h = 6.626 x 10 3 4 J-s c = 2.998 x 108 m-s ' 0 °C = 273.15 K 1 atm = 760 mmHg EQUATIONS ,\nKv = nF i 1A 1 H 1.008 3 Li — + constant IT) r JLIVIVJUH^ i /\i>i_jJL ur i niL JLI^JLIVIJLIII 1 » 2 2A 4 Be 13 3A 5 B 14 4A 6 C 15 5A 7 N is 16 6A 8 O 17 7A 9 F 8A 2 He 4.003 10 Ne 6.941 9.012 10.81 12.01 14.01 16.00 19.00 20.18 11 Na 12 Mg 13 Al 14 Si 15 P 16 S 17 Cl 18 Ar 22.99 24.31 19 K 20 Ca 3 3B 21 Sc 4 4B 22 Ti 5 5B 23 V 6 6B 24 Cr 7 7B 25 Mil 8 8B 26 Fe 9 8B 27 Co 10 8B 28 Ni 11 IB 29 Cu 12 2B 30 Zn 26.98 28.09 30.97 32.07 35.45 39.95 31 Ga 32 Ge 33 As 34 Se 35 Br 36 Kr 39.10 40.08 44.96 47.88 50.94 52.00 54.94 55.85 58.93 58.69 63.55 65.39 69.72 72.61 74.92 78.96 79.90 83.80 37 Rb 38 Sr 39 Y 40 Zr 53 87.62 88.91 107.9 112.4 114.8 118.7 Sb 121.8 Te 127.6 I 126.9 54 Xe 85.47 106.4 50 Sn 52 102.9 49 In 51 101.1 46 Pd 48 (98) 44 Ru 47 95.94 43 Tc 45 Rh 92.91 42 Mo 91.22 41 Nb 131.3 55 Cs 56 Ba 57 72 73 74 Hf Ta W 76 Os 77 Ir 78 La 75 Re 79 Au 80 Hg 81 Tl 82 Pb 83 Bi 84 Po 85 At 86 Rn Pt Cd 132.9 137.3 138.9 178.5 180.9 183.8 186.2 190.2 192.2 195.1 197.0 200.6 87 88 Ra 89 Ac 104 Rf 105 Db 106 S? (261) 107 Bh 108 Hs 109 Mt 110 111 112 114 (269) (272) (277) (2??) Fr (223) (226) (227) 58 Ce 59 Pr (262) 60 Nd 61 Pm (262) 62 Sm (265) 63 Eu (266) 64 Gd 65 Tb 66 140.1 140.9 144.2 (145) 150.4 152.0 157.3 158.9 Dy 162.5 90 Th 91 Pa 92 U 93 Np 94 Pu 95 Am 96 Cm 97 Bk 98 Cf 232.0 Page 2 (261) 231.0 238.0 (237) (244) (243) (247) (247) (251) 204.4 207.2 209.0 164.9 68 Er 167.3 69 Tm 168.9 173.0 175.0 99 Es 100 Fm 101 Md 102 No 103 Lr 67 Ho (252) (257) (258) 70 Yb (209) (259) (210) (222) 71 Lu (262) Not valid for use as an USNCO Olympiad National Exam after April 19, 2004. DIRECTIONS When you have selected your answer to each question, blacken the corresponding space on the answer sheet using a soft, #2 pencil. Make a heavy, full mark, but no stray marks. If you decide to change an answer, erase the unwanted mark very carefully. There is only one correct answer to each question. Any questions for which more than one response has been blackened will not be counted. Your score is based solely on the number of questions you answer correctly. It is to your advantage to answer every question. 1. Which element is obtained commercially from seawater? (A) bromine (B) gold (C) iron (D) oxygen 2. Which solution can serve as both reactant and indicator when it is used in redox titrations? (A) FeNH4(S04)2 (B) KMnO4 (C) H2C204 (D) Na2S2O3 (B) N 2 OandH 2 O (C) NOandH 2 (D) N2, H 2 andO 2 (A) 3 (C) Ni (D) Zn (A) Blanket it with CO2 (B) Blow on it. (C) Dump sand on it. (D) Pour water on it. 5. Which letter indicates where a thermometer should be placed to determine the boiling point of a distillate? (B) 6 (C) 12 (D) 18 9. An ionic compound contains 29.08% sodium, 40.56% sulfur and 30.36% oxygen by mass. What is the formula of the sulfur-containing anion in the compound? 4. Which method should be used to extinguish burning magnesium metal? (A) S2032 (B) S2042 (C) S2052 (D) S2062 Vapor pressure (mmHg) 10. A solution is prepared containing a 2:1 mol ratio of C2H4Br2 173 dibromoethane (C2H4Br2) and dibromopropane (C3H6Br2). C3H6Br2 127 What is the total vapor pressure over the solution assuming ideal behavior? I (C) C (B) Mn _ Br2 + _ OH' -» _ Br + _ BrO3" + _ H2O is balanced with the smallest integer coefficients? (A) N 2 andH 2 O (B) B (A) Ca 8. What is the coefficient for OH" after the equation 3. What is formed when a solution of NH4NO2 is heated gently? (A) A 7. A 1.871 gram sample of an unknown metallic carbonate is decomposed by heating to form the metallic oxide and 0.656 g of carbon dioxide according to the equation MCO3(s) -> MO(s) + CO2(g) What is the metal? (A) SOOmmHg (B) 158mmHg (C) ISOmmHg (D) 142mmHg (D) D 6. A 50 mL sample of gas is collected over water. What will be the effect on the calculated molar mass of the gas if the effect of the water vapor is ignored? It will be (A) high because of the mass of water in the collection flask. (B) high because of omitting the vapor pressure of the water in the calculation. (C) low because of the mass of water in the collection flask. 11. A solution of magnesium chloride that is 5.10% magnesium by mass has a density 1.17 g/mL. How many moles of Cl" ions are in 300. mL of the solution? (A) 0.368 (B) 0.627 (C) 0.737 (D) 1.47 12. Which aqueous solution has a freezing point closest to that of 0.30 MC 12 H 22 O n ? (A) 0.075 M A1C13 (B) 0.15MCuCl2 (C) 0.30MNaCl (D) 0.60 M C6H12O6 (D) low because of omitting the vapor pressure of the water in the calculation. Not valid for use as an USNCO Olympiad National Exam after April 19, 2004. Page 3 13. An unknown gas is placed in a sealed container with a fixed volume. Which of the characteristics listed change(s) when the container is heated from 25 °C to 250 °C? I The density of the gas II The average kinetic energy of the molecules III The mean free path between molecular collisions (B) II only (C) III only (D) I and II only 14. Which gas has the same density at 546 °C and 1.50 atm asthatofO 2 gasatSTP? (B) NH3 (A) S°20oK is smaller because entropy decreases as temperature increases. (B) S°20oK is smaller because the surroundings are more disordered at higher temperatures. (A) I only (A) N2 20. Which is the best description of the relationship between the absolute entropies, S°, of solid water at 100 K and at 200 K? (C) S02 (D) S03 15. Which plot involving vapor pressure (VP) and absolute temperature results in a straight line? (A) VPvsT (B) V P v s T 1 (C) In V P v s T (D) In V P v s T 1 (C) S°IOOK = S°200K = because water is in the solid phase at both temperatures. (D) S°200K is larger because the vibration of the molecules increases as temperature increases. 21. For the reaction, CH4 + C12 -> CH3C1 + HC1 which expression gives AH? Bond dissociation energies C-H C-C1 C1-C1 H-C1 kJ-mol 1 413 328 242 431 (A) AH = (413 + 328) - (242 + 431) (B) AH = (413 - 328) - (242 - 431) 16. For a substance with the values of AHvap and ASVap given below, what is its normal boiling point in °C? (AHvap= 59.0 kJ-mol >; ASvap = 93.65 J-mor1 -K'1) (A) 357 (B) 630 (C) 1314 (D) 1587 17. What is the order of the boiling points (from lowest to highest) for the hydrogen halides? (A) HF < HCK HBr < HI (B) HKHBr<HCKHF (C) H C K H F < H B r < H I (D) HCKHBr<HKHF 18. Of the three types of cubic lattices, which have the highest and lowest densities for the same atoms? Highest Lowest (C) AH = (413-242)-(328-431) (D) AH-(413+ 242)-(328+ 431) 22. Which phase change for water has positive values for both AH° and AG°? (A) (1)-> (s) at 250 K (B) (1)-> (s) at 350 K (C) (1)-> (g) at 350 K (D) (1)-»(g) at 450 K 23. When solid CuSO4 dissolves in water to make a 1M solution, the temperature of the system increases. When solid NH4NO3 dissolves in water to make a 1 M solution, the temperature of the system decreases. Which statement(s) must be correct for these dissolving processes? I AH° values for both processes have the same sign. II AG° values for both processes have the same sign. (A) simple cubic body-centered cubic (B) face-centered cubic simple cubic (C) body-centered cubic face-centered cubic (A) I only (B) II only D) face-centered cubic body-centered cubic (C) Both I and II (D) Neither I nor II 19. For which reaction is AH (enthalpy change) most nearly equal to AE (internal energy change)? 24. Which set of relationships could apply to the same electrochemical cell? (A) H2(g) + l/202(g) - H20(g) (A) AG°>0;E° = 0 (B) AG°<0;E° = 0 (B) Cl2(g) + F2(g) - 2ClF(g) (C) A G ° > 0 ; E ° > 0 (D) A G ° < 0 ; E ° > 0 (C) H20(l) - H20(g) (D) 2S03(g) -> 2S02(g) + 02(g) Page 4 25. The rate constant for a reaction is affected by which factors? I increase in temperature II concentration of the reactants 111 presence of a catalyst (A) I and II only (B) I and III only (C) II and III only (D) I, II and III Not valid for use as an USNCO Olympiad National Exam after April 19, 2004. 26. The rate data given were obtained for the reaction, 2NO(g) + 2H2(g) - N,(g) + 2H20(g) What is the rate law for this reaction? NO pressure (atm) H2 pressure (atm) Rate (atm* sec"1) 0.375 0.500 6.43 xlO- 4 0.375 0.250 3.15X10" 4 0.188 0.500 1.56X10" 4 (A) = k: (B) Rate-1 (C) 27. What is the order of a reaction that produces the graphs shown? 31. H2S(aq) ^ HT(aq) + HS'(aq) K = 9.5xlO- 8 HS-(aq) ^ HT(aq) + S2 (aq) K^l.OxlO'19 Given the equilibrium constants provided, what is the equilibrium constant for the reaction; S 2 (aq) + 2H+(aq) ^ H2S(aq) K =? (A) 9.5 x 10'27 (B) 9.7 x lO'14 (C) 9.5 x 1011 (D) 1.0xl0 2 ( 32. Calculate the hydronium ion concentration in 50.0 mL of 0.10MNaH 2 AsO 4 . (KJ = 6.0 x lV3, K2 = 1.1 x lO'7 K3 = 3.0 x 10"12) (A) 2.4 xlO- 2 (B) 1.6X10' 3 (C) 1.0 xlO" 4 (D) 2.5 xlO' 5 33. When the acids; HC1O3, H3BO3, H3PO4, are arranged in order of increasing strength, which order is correct? (A) H3BO3 < H3PO4 < HC1O3 (B) HC1O3 < H3BO3 < H3PO4 (A) zero order (B) first order (C) H3PO4 < HC1O3 < H3BO3 (C) second order (D) some other order (D) H3BO3 < HC1O3 < H3PO4 28. What is the rate law for the hypothetical reaction with the mechanism shown? intermediate 1 fast equilibrium 2A intermediate 2 slow intermediate 1 + B A2B2 fast intermediate 2 + B 34. A buffer solution results from mixing equal volumes of which solutions? I 0.1OMHC1 and 0.20 MNH 3 II 0.10 M HNO2 and 0.10 M NaNO2 III 0.20 M HC1 and 0.10 M NaCl (A) (B) Rate = [B]2 (A) II only (B) I and II only (C) Rate = k[A][B] (D) Rate = k[A]2[B] (C) I and III only (D) I, II and III 29. According to the Arrhenius equation: k = Ae"Ea/RT, a plot of In k against 1/T yields (A) Ea as the slope and A as the intercept (B) Ea/R as the slope and A as the intercept (C) Ea/R as the slope and In A as the intercept (D) -Ea/R as the slope and In A as the intercept 35. A solution is 0. 1 0 M in Ag+, Ca2+, Mg*, and A13+ ions. Which compound will precipitate at the lowest [PO43 ] when a solution of Na3PO4 is added? (A) Ag 3 P0 4 (K a p =lxia 1 6 ) (B) Ca 3 (P0 4 ) 2 (K s p =lxia 3 3 ) (C) Mg 3 (P0 4 ) 2 (K^lxlO- 24 ) (D) 30. Curves with the shape shown are often observed for reactions involving catalysts. The level portion of the curve is best attributed to the fact that 36. Which salt is significantly more soluble in a strong acid than in water? (A) PbF2 Reactant concentration (A) product is no longer being formed. (B) the reaction has reached equilibrium. (C) all the catalytic sites are occupied. (D) all the reactant has been consumed. (B) PbCl2 (C) PbBr2 (D) PbI2 37. What is the standard cell potential for the reaction, 2Cr(s) + 3Sn2+(aq) -» 3Sn(s) + 2Cr3+(aq) given the E° values shown? Cr^aq) + 3e~ Cr(s) -0.744 V Sn2+(aq) + 2e~ • Sn(s) -0.141 V (A) 0.945V (B) 0.603V (C) -0.603V (D) -0.945V Not valid for use as an USNCO Olympiad National Exam after April 19, 2004. PageS 38. How many electrons are needed in the balanced halfreaction for the oxidation of ethanol to acetic acid? C2H5OH -* CH3COOH (A) 1 (B) 2 (C) 3 (B) Cu2+(aq) (C) H+(aq) (D) Zn2+(aq) (A) N (C) 6.1 x 104 (D) 3.8 x 109 41. When an aqueous solution of potassium fluoride is electrolyzed, which of the following occurs? (A) O2 and H+ are produced at one electrode and H2 and OH" are formed at the other. (B) O2 and OH" are produced at one electrode and H2 and H+ are formed at the other. (C) Metallic K is formed at one electrode and O2 and H+ are formed at the other. (D) Metallic K is produced at one electrode and elemental F2 is produced at the other. 42. A CuSO4 solution is electrolyzed for 20. minutes with a current of 2.0 ampere. What is the maximum mass of copper that could be deposited? (A) 0.20 g (B) 0.40 g (C) 0.79 g (D) 1.6g 43. Which experimental evidence most clearly supports the suggestion that electrons have wave properties? (A) diffraction (A) 0 (D) deflection of cathode rays by a magnet 44. Which quantum number determines the number of angular nodes in an atomic orbital? (C) m, (D) ms 45. Which element exhibits the greatest number of oxidation states in its compounds? (A) Ca Page 6 (B) V (C) 4 (D) 6 (B) (Q 2 »F (D) 49. According to the Lewis dot : o : : :c :N : structure shown, what are the formal charges of the O, C and N atoms, respectively, in the cyanate ion? (A) 0,0,0 (B) -1,0,0 (C) -1,+1, (D) +1,0,-2 50. The hybridization of As in AsF5 is best described as (A) sp3 (B) sp4 (C) dsp3 (D) d2sp3 51. In which species do the atoms NOT lie in a single plane? (A) BF3 (B) PF3 (C) C1F3 (D) XeF4 52. For which compound does the reaction, MCO3(s) MO(s) + CO2(g) occur most readily? (A) BeCO3 (B) MgCO3 (C) CaCO3 (D) BaCO3 53. The color of Co(H2O)62+ is best attributed to electronic transitions (A) between different n levels in the metal. (B) between the metal's d orbitals. (D) during ionization. (C) photoelectric effect (A) n (B) 2 (C) from the Co2+ ion to water molecules. (B) emission spectra (B) 1 (D) CI 47. How many unpaired electrons are in a gaseous Fe2+ ion in its ground state? (A) >2 N (B) 22 (C) S 48. Which species is most likely to lose a positron (|3+)? 40. The standard potential for the reaction Cl2(g) + 2Br-(aq) ---> Br2(l) + 2Q-(aq) is 0.283 volts. What is the equilibrium constant for this reaction at 25 °C? (A) 1 . 6 x l 0 5 (B) P (D) 4 39. Which is the weakest oxidizing agent in a 1 M aqueous solution? (A) Ag+(aq) 46. Of the elements given, which has the lowest ionization energy? (C) Cu 54. When the carbon-oxygen bonds in the species; CH3OH, CH2O and CHO2" are arranged in order of increasing length, which is the correct order? (A) CH3OH < CH2O < CHO2" (B) CH2O < CH3OH < CHO2(C) CHO2- < CH3OH < CH2O (D) CH2O < CHO2- < CH3OH (D) As Not valid for use as an USNCO Olympiad National Exam after April 19, 2004. 55. How many different trichlorobenzenes, C6H3C13, can be formed? (A) 1 (B) 2 (C) 3 (D) 4 56. What organic product is formed from the mild oxidation of a secondary alcohol? (A) acid (B) aldehyde (C) ether (D) ketone 57. The compound with the formula, H2NCH2CH2COOH, is best classified as a(n) (A) amide (B) amino acid (C) fatty acid (D) nucleic acid 58. The reaction between which pair of reactants occurs the fastest for [OH'] = 0.010 M? (A) CH3CH2CH2CH2C1 + OH~ (B) (CH3)3CC1 + OH(C) CH3CH2CH2CH2Br + OH~ (D) (CH3)3CBr + OH59. What is the major organic product formed from the reaction of CH3CH-CH2 and HC1? (A) CH3CHC1CH3 (B) CH3CH2CH2C1 (C) CH3CHC1CH2C1 (D) CH2C1CH=CH2 60. Fats and oils are formed from the combination of fatty acids with what other compound? (A) cholesterol (B) glucose (C) glycerol (D) phenol END OF TEST Not valid for use as an USNCO Olympiad National Exam after April 19,2004. Page 7