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Last Name: _____________________________ First Name: _______________ Lab Sec. # ____ TA: ____________________ Lab day/time: _____________ Dr. Enderle CHEMISTRY 2A (D) Final Exam – Winter 2009 Multiple Choice Circle one Instructions: CLOSED BOOK EXAM! DO NOT OPEN the exam until instructed to do so. No books, notes, or additional scrap paper are permitted. All information required is contained on the exam. Place all work in the space provided. If you require additional space, use the back of the exam. A scientific calculator may be used (if it is a programmable calculator, its memory must be cleared before the exam). Sharing of calculators is not allowed. (1) (2) (3) (4) (5) Read each question carefully (27 problems, 15 pages). ANSWER ALL THE QUESTIONS YOU ARE SURE OF FIRST, AND THEN USE THE REMAINING TIME FOR THE REST. Please show all relevant work where it is indicated for full credit. The last 2 pages contain a periodic table and some useful information. You may remove them for easy access and for scratch. If you finish early, RECHECK YOUR ANSWERS! UC Davis is an Honor Institution Possible Points Points 1. a b c d e 2. a b c d e 3. a b c d e 4. a b c d e 5. a b c d e 6. a b c d e 7. a b c d e 8. a b c d e 9. a b c d e 10. a b c d e 11. a b c d e # 1-13 (3 points each) / 39 12. a b c d e # 14-19 (5 points each) / 30 13. a b c d e # 20 (6 points) / 06 1 - 1 3 total points: # 21 (42 points) / 42 14. a b c d e # 22 (10 points) / 10 15. a b c d e # 23 (10 points) / 10 16. a b c d e # 24 (06 points) / 06 17. a b c d e # 25 (30 points) / 30 18. a b c d e # 26 (06 points) / 06 19. a b c d e # 27 (16 points) / 16 1 4- 1 9 total points: Total Score (195) / 195 WINTER 2009 FINAL CHEM 2A (Page 2 of 15) Concepts: Multiple Choice Questions 1-13: 3 points each (no partial credit) 1. Write the symbol of the species that has 28 protons, 26 electrons, and 32 neutrons. 58 Fe2+ 60 Ni260 Ni2+ 60 Fe2+ 60 Ni3+ a) b) c) d) e) 2. In the reaction, H2O2 H2O + 1/2O2 oxygen is: a. Reduced b. Oxidized c. Both a. and b. d. Neither a. nor b. e. Annihilated 3. How many σ bonds does the molecule of guanine have? a) b) c) d) e) 4. 17 2 3 4 0 N C C NH HC C N H C N NH2 Choose the INCORRECT formula-name combination. a. b. c. d. Na2CO3 P2O5 FeBr2 N2O3 e. K3N 5. O sodium carbonate diphosphorus pentoxide iron dibromide dinitrogen trioxide potassium nitride In which of the following compounds does chlorine have the highest oxidation number? (a) ClO2 (b) Cl2 (c) FeCl3 (d) KClO3 (e) Mg(ClO)2 WINTER 2009 6. 7. FINAL CHEM 2A (Page 3 of 15) Which of the following reactions is NOT a redox reaction? (a) 5 I– (aq) + IO3– (aq) + 6 H+ (aq) 3 I2 (s) + 3 H2O (l) (b) Zn (s) + Cu2+ (aq) Zn2+ (aq) + Cu (s) (c) 2 H2O2 (aq) 2 H2O (l) + O2 (g) (d) BaCl2 (aq) + Na2SO4 (aq) BaSO4 (s) + 2NaCl (aq) (e) CH3COOH (aq) + 2 O2 (g) 2 CO2 (g) + 2 H2O (l) Which statement is FALSE about the 5dxy orbital? (a) It has a nodal plane in the xz plane. (b) It has a nodal plane in the yz plane. (c) For an electron in the 5dxy orbital there is a higher probability of finding the electron farther from the nucleus than if it is in the 5s orbital. (d) It can hold a total of 10 electrons. (e) None of the above. 8. Choose the species from which one electron could most easily be removed. (a) Cl (b) Na+ (c) Na (d) K (e) Ar 9. Which of the following has the largest radius? (a) As3– (b) Br– (c) Sr2+ (d) Cl (e) They all have approximately the same size 10. Using the VSEPR theory, which one of the following chemical species would you expect to have a dipole moment (polar)? a. I3– b. O3 c. CO2 d. CH4 e. None of the above WINTER 2009 11. FINAL CHEM 2A (Page 4 of 15) What is the bond order of the nitrogen-oxygen bonds in the nitrate ion? (a) 2, 1, and 1 (b) 1, 2, and 2 (c) 1.33 (d) 1 (e) 2 12. 13. Choose the INCORRECT statement about the molecule of HCN. a. There are a total of two σ bonds in the molecule. b. There are a total of two π bonds in the molecule. c. There is a lone pair on nitrogen. d. The molecule is bent. e. The carbon atom has sp hybridization. Which of the following is NOT TRUE about a mixture of gases? a. The sum of the partial pressures of each gas is equal to the total pressure. b. The sum of the moles of each gas is equal to the total number of moles. c. The sum of the temperature of each gas is equal to the total temperature. d. The sum of the partial volumes of each gas is equal to the total volume. e. All of the above statements are true. WINTER 2009 FINAL CHEM 2A (Page 5 of 15) Calculations: Multiple Choice Questions 14-19: 5 points each (no partial credit) 14. A hypothetical element, E, has two stable isotopes: E-38 = 38.012 u 75.68% E-46 = 45.981 u 24.32% The element’s atomic mass would be closest to which element? (a) K (b) Ar (c) Ca (d) Sc (e) Sr 15. Find the empirical formula for a compound with the following mass composition: K 42.4%, Fe 15.2%, C 19.5% and N 22.8%. a. KFeCN b. K4FeC6N6 c. KFeC6N6 d. K4FeCN6 e. K4FeC6N WINTER 2009 16. FINAL CHEM 2A (Page 6 of 15) You have a 1.212 M stock aqueous solution of Sr(OH)2. What volume of the stock solution (in mL) must be diluted with water to prepare 50.00 mL of a solution that has a hydroxide concentration [OH–] = 0.2000 M? 17. a. 6.455 mL b. 1.294 mL c. 2.528 mL d. 4.125 mL e. 8.173 mL When chlorine is added to acetylene, 1,1,2,2-tetrachloroethane is formed: 2 Cl2(g) + C2H2(g) C2H2Cl4(l) How many liters of chlorine gas at STP will be needed to make 75.0 grams of C2H2Cl4? a. 10.0 L b. 20.0 L c. 30.0 L d. 40.0 L e. 50.0 L WINTER 2009 18. 19. FINAL CHEM 2A (Page 7 of 15) Consider an electron moving at 1 x 106 m/s. Find its wavelength in angstroms. a. 1Å b. 3Å c. 5Å d. 7Å e. 9Å The energy of a photon is used to completely remove the electron of a hydrogen atom. What is the wavelength of the photon in nanometers if the electron is removed from its second orbit? a) b) c) d) e) 365 nm 410 nm 434 nm 486 nm 656 nm WINTER 2009 FINAL CHEM 2A (Page 8 of 15) 20. (6 points) Fill in the blanks with the correct ground state electron configuration (noble gas configuration) for the given atom or the atom for the given ground state electron configuration of the neutral atom. Atom Electron Configuration Sn [Ar] 3d10 4s1 21. (42 points) Fill in the following table (see the ClF3 example). For the determination of formal charge(s) consider the Lewis formula with the smallest formal charges (lowest energy). Molecule Electron-Group Geometry (central atom) Molecular Geometry Ideal Bond Angles ClF3 TrigonalBipyramidal T- shape 90º , 1 80º CCl2Br2 PCl3 CO2 H 2O XeF4 SF4 Formal Oxidation HybridPolar or Charge(s) Number ization Nonpolar of the of the (central Molecule underlined underlined atom) element element polar sp3d 0 -1 WINTER 2009 FINAL CHEM 2A (Page 9 of 15) Partial Credit. Show ALL Your Work. Explain. 22. (10 points) If 10.0 g of sodium hydrogen carbonate is added to 450 mL of a 0.155 M aqueous solution of copper(II) nitrate and left to react according to the reaction: 2NaHCO3(aq) + Cu(NO3)2(aq) CuCO3(s) + 2NaNO3(aq) + H2O(l) + CO2(g) How many liters of carbon dioxide are produced at STP? V= WINTER 2009 FINAL CHEM 2A (Page 10 of 15) 23. (10 points) A civil engineer wants to reduce odors at a wastewater treatment plant by adding hydrogen peroxide to the sewage. The hydrogen peroxide is delivered as 50% by mass solution, but for maintenance and safety issues, the H2O2 is diluted to a 3% by mass solution. If the engineer needs 20.0 gallons of the 3% by mass aqueous solution of H2O2, how many gallons of water does the engineer need to add to the 50% solution? (Density of 50% solution = 1.197 g/mL; density of 3% solution = 1.015 g/mL) Volume of water = 24. (6 points) Consider the molecule of ozone, O3. A) Draw its two resonance Lewis electron dot diagrams. B) What is the electron group geometry of its central atom? C) What is its molecular geometry? D) What is the hybridization of its central atom? E) What is the ideal bond angle? F) Is it polar or nonpolar molecule? A) B) C) D) E) F) WINTER 2009 25. FINAL CHEM 2A (Page 11 of 15) (30 points) Complete the MO energy level diagram for the cation B2+. a. Fill in the electrons using arrows (↑ and/or ↓) for the atomic and molecular orbitals. b. Designate all the energy levels (i.e., σ2s*, π2p, σ2s, etc.) c. Calculate the bond order for B2+. d. Is B2+ a paramagnetic or diamagnetic chemical species? a. and b. 2p 2p E 2s B c. d. Bond order for B2+ = Paramagnetic or Diamagnetic? Answer: 2s B2 + B+ WINTER 2009 FINAL CHEM 2A (Page 12 of 15) 26. (6 points) Write the possible four quantum numbers n, l, ml, and ms for each of the following electrons. 2s 4d 5f WINTER 2009 27. FINAL CHEM 2A (Page 13 of 15) (16 points) Balance the following chemical equation by the half-reaction method and show your work. Next, answer the following questions. CH4O + O2 CO2 + H2O Note! The above chemical equation is very easy to balance just by inspection. You are NOT asked to balance it by the inspection method. Balancing it by the inspection method will result in zero points for credit. a. The oxidizing chemical species is: b. The reducing chemical species is: c. The name of the oxidized element is: d. The name of the reduced element is: e. The oxidant’s molecular formula is: f. The reductant’s molecular formula is: g. The name of the element that gains electrons is: h. The name of the element that loses electrons is: i. The chemical species that causes oxidation is: j. The chemical species that causes reduction is: k. The oxidation number of ____ (give the chemical symbol of the element) increases from ____ to ____ l. The oxidation number of ____ (give the chemical symbol of the element) decreases from ____ to ____ WINTER 2009 FINAL CHEM 2A (Page 14 of 15) Solubility rules: Compounds which are soluble or mostly soluble: • Group 1, NH4+, chlorates, acetates, nitrates • Halides (except Pb2+, Ag+, and Hg22+) • Sulfates (except Sr2+, Ba2+, Pb2+, and Hg22+) Compounds which are insoluble: • • Hydroxides, sulfides (except above rule, and sulfides of group 2) Carbonates, phosphates, chromates (except above rules) Some useful equations and data: PLEASE NOTE: Important values and equations required for calculations are given with the respective problem. The following may or may not be of any use. λ= h mυ d= PM RT Molarity = Moles Liter n (moles) = mass (g) molar mass (g/mol) PV = nRT NA = 6.022 x 1023 h = 6.626x10-34 Js 1 J = 1 kg m2 s-2 = 1 N m mL∙M = mmol Ptotal = P1 + P2 + … TK = ToC + 273 R = 0.0821 L atm mol-1 K-1 1 nm = 10-9 m c = 3.00 x 108 m s-1 c = νλ xA = nA / ntot = PA / Ptot Ephoton = hν Rate2/Rate1=(M1/M2)1/2 Z2 En = − RH 2 n d= m V ∆x ⋅ ∆p = RH = 2.179 x 10 -18 J me = 9.109387x10-28 g h 4π 1 atm = 760 mmHg 1 g = 6.022x1023 amu ∆ p = m ∆υ ∆E = RH(1/ni2 – 1/nf2) 1 Å = 10-10 m % Yield = Actual Yield Theoretical Yield x100 WINTER 2009 FINAL CHEM 2A (Page 15 of 15) Potentially Useful Information (You may remove this page for ease of access) Key 1 Atomic Number Symbol Atomic Mass Electronegativity H 1.008 2.20 3 2 He 4.003 - 4 5 6 7 8 9 10 Li Be B C N O F Ne 6.941 0.98 9.012 1.57 10.81 2.04 12.01 2.55 14.01 3.04 16.00 3.44 19.00 3.98 20.18 - 11 Na Mg Al Si 14 15 16 S Cl Ar 22.99 0.93 24.31 1.31 26.98 1.61 28.09 1.90 30.97 2.19 32.06 2.58 35.45 3.16 39.95 - 19 12 Ti 22 23 V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr 39.10 0.82 40.08 1.00 44.96 1.36 47.90 1.54 50.94 1.63 52.00 1.66 54.94 1.55 55.85 1.83 58.93 1.88 58.70 1.91 63.55 1.90 65.38 1.65 69.72 1.81 72.59 2.01 74.92 2.18 78.96 2.55 79.90 2.96 83.80 - 38 39 52 53 87.62 0.95 88.91 1.22 127.6 2.1 126.9 2.66 85.47 0.82 55 Cs 56 Ba Y 71 Lu 132.9 0.79 87 137.3 0.89 175.0 1.27 88 103 (223) 0.7 (226) 0.9 (260) - Fr Ra Lr 40 Zr 91.22 1.33 72 Hf 178.5 1.3 41 Nb 92.91 1.6 73 Ta 42 Mo 95.94 2.16 74 W 25 43 Tc (98) 1.9 75 Re 104 180.9 1.5 105 183.9 2.36 106 186.2 1.9 107 - - - - Unq 57 Unp 58 Unh 59 Uns 60 26 44 Ru 101.1 2.2 76 Os 190.2 2.2 - 61 27 45 Rh 102.9 2.28 77 Ir 192.2 2.20 28 46 Pd 106.4 2.20 78 Pt 195.1 2.28 29 47 Ag 107.9 1.93 79 Au 197.0 2.54 30 48 Cd 112.4 1.69 80 Hg 200.6 2.00 31 49 In 114.8 1.78 81 Tl 204.4 2.04 32 50 Sn 33 51 Sb 118.7 1.96 121.8 2.05 82 83 207.2 2.33 209.0 2.02 Pb Bi 34 Te 84 Po (209) 2.0 35 18 Sc Sr 24 17 Ca 37 21 P K Rb 20 13 I 85 At (210) 2.2 109 Une - 62 63 64 65 66 67 68 69 70 La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb 138.9 1.10 140.1 1.12 140.9 1.13 144.2 1.14 (145) 1.13 150.4 1.17 152.0 1.2 157.3 1.20 158.9 1.2 162.5 1.22 164.9 1.23 167.3 1.24 168.9 1.25 173.0 1.1 89 Ac Th 90 Pa 91 92 U Np 93 Pu 94 Am 95 Cm 96 Bk 97 Cf 98 Es 99 Fm 100 Md 101 No 102 (227) 1.1 232.0 1.3 (231) 1.5 238.0 1.38 (237) 1.36 (244) 1.28 (243) 1.3 (247) 1.3 (247) 1.3 (251) 1.3 (252) 1.3 (257) 1.3 (258) 1.3 (259) 1.3 36 54 Xe 131.3 86 Rn (222) -