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Unformatted text preview: FINAL EXAM - VERSION A
CHEN 1211 Profs. George & Bowman Wednesday, December 20, 2006 1:30PM to 4:00PM Answer all questions on the scantron answer sheet by filling in the proper bubble with a number 2 pencil. If you change your answer, please erase the undesired mark thoroughly. Be sure to fill in the boxes for your student number, name and lab section; then fill in the corresponding bubbles beneath them correctly. A periodic table with atomic numbers and masses is attached to the back of this exam. There are 12 exam pages and 28 questions. The last question asks for the version of your exam. Check to be sure you have answered all the questions. Please note the point values of each question. Useful Information: Avogadro's Number = 6.022 x 10 mol-1 Number of Moles = Concentration x Volume
23 Planck's Constant, h= 6.63 x 10-34 Js c = λν = 3 x 108 m/s E = hν λ = h/mv E = mc2 1 amu = 1.660539 x 10-27 kg 1 cal = 4.184 J 1 eV = 1.602 x 10-19 J Boltzmann's Constant, k= 1.380650 x 10-23 J/K 1 J = 1 kg m2/s2 Spherical Nodes = n - l - 1 Planar Nodes = l PV= nRT Gas Constant, R= 0.08206 L atm/mol K Gas Constant, R= 8.314 J/mol K STP is 1.0 atm and 0oC. K = oC + 273.15 760 mm Hg = 1.0 atm ∆G = ∆H –T∆S W = -P∆V ∆E = q + w = q - P∆V 1 1/λ = R[1/m2 - 1/n2] R = 1.097 x 10-2 nm-1 n>m pH = -log[H+] = -log[H3O+] Kp = Kc(RT)∆n Ka = [H3O+][A-]/[HA] Kw = [H3O+] [OH-] = KaKb = 10-14 Kc = kf/kr Henderson-Hasselbalch: pH = pKa + log ( [A-]/[HA] ) Zero Order Reaction: [A]0 = [A] – kt Zero Order Reaction: t1/2= [A]o / 2k First Order Reaction: ln[A] =ln[A]o –kt First Order Half-Life t1/2 = 0.693/k Second Order Reaction: 1/[A] = 1/[A]o + kt Second Order Half-Life t1/2 = 1/k[A0] k = Ae-E/RT ln (k2/k1) = (-Ea/R) (1/T2 - 1/T1) BCC unit cell edge = 4r/(3)1/2 Unit cells: FCC unit cell edge= 2(2)1/2 r ; Electron Charge = 1.602176 x 10-19 C Faraday's Constant, F= 96,485 C/mol ∆G = -nFE E = E0 - [0.0592 V/n] log Q pH = (Ecell - Eref)/0.0592 V Ek=3RT/2NA u= 3RT M x= −b ± b 2 − 4ac 2a ⎛ P ⎞ ∆H vap ⎛ 1 1 ⎞ ⎜ − ⎟ ln⎜ 1 ⎟ = R ⎝ T2 T1 ⎠ ⎝ P2 ⎠ 2 1. (12 Points) NaCl is an ionic solid. The density of NaCl is 2.17 g/cm3. How many individual NaCl units (diatomic components) are there per cm3 in the NaCl ionic solid? (a) 3.7 x 10-2 cm-3 (b) 2.7 x 101 cm-3 (c) 6.4 x 1018 cm-3 (d) 2.2 x 1022 cm-3 (e) 5.7 x 1023 cm-3 2. (8 Points) What is the sum of the coefficients when the following equation is balanced using the lowest, whole numbered coefficients? ___PH3(g) + ___O2(g) → ___P4O10(s) + ___H2O(g) (a) 10 (b) 12 (c) 19 (d) 22 (e) 25 3. (12 Points) Combustion analysis of an unknown compound containing only carbon and hydrogen produced 1.138 g of CO2 and 0.2902 g of H2O. What is the empirical formula of the compound? (a) CH2 (b) C4H5 (c) C4H10 (d) C5H2 (e) C5H4 3 4. (8 Points) How many moles of BCl3 are needed to produce 25.0 g of HCl(aq) in the following reaction? BCl3(g) + 3H2O(l) → 3HCl(aq) + B(OH)3(aq) (a) 0.229 mol (b) 0.686 mol (c) 2.06 mol (d) 4.38 mol (e) 5.29 mol 5. (12 Points) For the third-shell orbital shown below, what are the principal quantum number, n, and the angular momentum quantum number, l? Remember that the number of spherical nodes is n - l - 1 and the number of planar nodes is l. (a) n =2, l =1 (b) n=2, l =2 (c) n=3, l =1 (d) n=3. l =2 (e) n=3, l =3 6. (12 Points) What is the ground-state electron configuration of tellurium (Te) with an atomic number of 52? (a) [Kr] 5s24d105p4 (b) [Kr]5s25p65d8 (c) [Kr]5s25p4 (d) [Kr] 5s24d105p44f14 (e) [Kr] 5s24d105p54f14 4 7. (12 Points) The Balmer-Rydberg equation can be extended to ions with only one electron, such as He+. For these ions, the Balmer-Rydberg equation has the form: 1/λ = Z2 R (1/m2 -1/n2) where R is the Rydberg constant, m and n are integers with n>m, and Z is the atomic number of the ion. What is the energy of the photon required to promote an electron in He+ from the 1s orbital to the 2p orbital? Remember that m and n correspond with the principal quantum numbers. (a) (3/4) hcR (b) 3 hcR (c) 4 hcR (d) 6 hcR (e) 12 hcR 8. (14 Points) The lattice energy for MgCl2(s) is based on the reaction: MgCl2(s) → Mg2+(g) + 2Cl-(g) Calculate the lattice energy for MgCl2(s) using a Born-Haber cycle and the following information: Mg(s) + Cl2(g) → MgCl2(s) Mg(s) → Mg(g) Mg(g) → Mg+(g) + eMg+(g) → Mg2+(g) + e(1/2) Cl2(g) → Cl(g) Cl(g) + e- → Cl-(g) (a) +641.6 kJ/mol (b) +1240.5 kJ/mol (c) +1882.1 kJ/mol (d) +2523.7 kJ/mol (e) +3255.8 kJ/mol -641.6 kJ/mol +147.1 kJ/mol +737.8 kJ/mol +1451.0 kJ/mol +121.7 kJ/mol -348.6 kJ/mol 5 9. (12 Points) What is the formal charge on the N atom in the most stable Lewis dot structure for the negative ion NCO- ? (a) -2 (b) -1 (c) 0 (d) +1 (e) +2 10. (12 Points) What is the molecular geometry of IF5? (a) Octahedral (b) Seesaw (c) Square pyramidal (d) Trigonal bipyramidal (e) Trigonal pymamidal 11. (12 Points) 1.00 mole of benzene is vaporized at a constant pressure of 1.00 atm and at its normal boiling temperature of 80.1°C. For this vaporization, 33.9 kJ are absorbed and P∆V for the vaporization process is equal to 2.90 kJ. What are ∆E and ∆H? (a) ∆E = 31.0 kJ and ∆H = 33.9 kJ (b) ∆E = 36.8 kJ and ∆H = 33.9 kJ (c) ∆E = 33.9 kJ and ∆H = 31.0 kJ (d) ∆E = 33.9 kJ and ∆H = 36.8 kJ (e) ∆E = 36.8 kJ and ∆H = 31.0 kJ 6 12. (14 Points) When 1.5 g of Ba(s) is added to 100.0 g of water in a container open to the atmosphere, the reaction shown below occurs: Ba(s) + 2 H2O(l) → Ba(OH)2(aq) + H2(g) The temperature of the resulting solution also rises from 22.00°C to 33.10°C. If the specific heat of the solution is 4.18 J/(g ⋅°C), calculate ∆H for the reaction per mole of Ba. (a) 431 kJ/mol (b) 425 kJ/mol (c) -425 kJ/mol (d) -431 kJ/mol (e) -470 kJ/mol 13. (8 Points) For which of the following processes is the sign of ∆S negative? (a) boiling of water (b) formation of snow from water vapor in clouds (c) melting of ice cream (d) sublimation of I2 (e) combustion of CH4 14. (14 Points) Calculate the cell potential, E, at 25°C for the electrochemical reaction: 2 Al(s) + 3 Fe2+(aq) → 2 Al3+(aq) + 3 Fe(s) You are given that [Fe2+(aq)] = 0.020 M and [Al3+(aq)] = 0.10 M. In addition, the standard reduction potentials are E0 = -1.66V for Al3+(aq) + 3e- → Al(s) and E0= -0.45V for Fe2+(aq) + 2e- → Fe(s). Remember that n is the total number of electrons transferred in the reaction. (a) +1.03 V (b) +1.15 V (c) +1.18 V (d) +1.22 V (e) +1.27 V 7 15. (12 Points) The following cell has a potential of +0.27 V at 25°C: Pt(s) | H2(1 atm)/H+(? M) || Ni2+(1 M) | Ni(s) What is the pH of the solution in the anode compartment? The standard reduction potentials are E0H2→H+ = 0 V and E0Ni2+→Ni = -0.26 V. (a) 3.6 (b) 4.8 (c) 6.3 (d) 7.9 (e) 9.0 16. (12 Points) A certain element has four isotopes with masses of 25.0, 27.5, 31.0 and 33.0 amu. The first isotope with a mass of 25.0 amu has a relative abundance of 30.0%. The second isotope with a mass of 27.5 amu has a relative abundance of 17.5%. If the average mass for this element is 29.5 amu, what is the relative abundance of the third isotope with a mass of 31.0 amu? (a) (b) (c) (d) (e) 52.5% 6.88% 10.7% 9.32% 45.6% 17. (12 Points) Cr exists in different oxidation states depending on the atoms that are bound to Cr. What is the sum of the oxidation states of Cr in the following three ions? Cr3+, Cr2O72-, and CrO4 2(a) (b) (c) (d) (e) +9 + 10 + 12 + 15 + 18 8 18. (12 Points) If 12.5% of the original amount of carbon-14 relative to carbon-12 remains in a certain organic sample, how old is the sample? The half life of carbon-14 is 5730 years. (a) (b) (c) (d) (e) 2,380 years 5,730 years 7,940 years 11,460 years 17,190 years 19. (12 Points) A certain isotope has a mass of 100.000 g/mol and decays through an alpha particle emission. The energy released is 1.24 x 1010 kJ/mol when this isotope decays. If the molar mass of a helium-4 atom is 3.998 g/mol, what is the total mass of all of the other products in addition to the alpha particle? (a) (b) (c) (d) (e) 94.62 g/mol 95.86 g/mol 96.00 g/mol 96.14 g/mol Not within 0.1 g/mol of any of the above 20. (8 Points) The following reaction between H2 and O2 was demonstrated many times in class. If 12.6 g of oxygen gas are consumed per second, then how many moles of water are generated every second? H2 + 1/2 O2 H2O (a) 3.2 moles of water generated per second (b) 0.39 moles of water generated per second (c) 0.32 moles of water generated per second (d) 1.26 moles of water generated per second (e) 0.79 moles of water generated per second 9 21. (8 Points) A container with a volume of 22.4L is filled with an ideal gas mixture of He, N2, O2, and Ar. If the container is at 250°C and 0.075 atm, then how many total moles of gas are in the container? (a) 0.039 moles (b) 1.8 moles (c) 0.018 moles (d) 1.0 moles (e) There is not enough information to determine the number of moles of gas 22. (8 Points) For a zero-order reaction, the rate constant is 0.45 moles / (L*minute) and the initial concentration of the reactant is 1.8 moles/L. How much time is required for this reactant to reach a concentration of 0.00 moles/L? (a) 18 minutes (b) 4.5 minutes (c) 4.0 minutes (d) 2.0 minutes (e) 0.045 minutes 23. (8 Points) Which of the following statements about equilibrium is TRUE? (a) The equilibrium constant of a reaction changes as the initial concentration of the reactants changes. (b) The rates of both the forward and reverse reactions are equal to zero at equilibrium. (c) The equilibrium constant for an exothermic reaction increases as the temperature increases. (d) The concentrations of all the reactants and products are equal at equilibrium. (e) The rates of the forward and reverse reactions are equal at equilibrium. 10 24. (12 Points) What ratio of acetate anion (Ac-) to acetic acid (HAc) is required to have a pH of 4.85? The Ka of acetic acid is 1.8x10-5. (a) 2.0x10-5 (b) 0.69 (c) 0.79 (d) 1.27 (e) Not within 10% of any of the above answers 25. (14 Points) A buffer is formed from 1.0 M NH4Cl and 0.75 M NH3. Kb of ammonia is 1.8x10-5. What is the pH of this buffer after 0.2 moles of NaOH is added per liter of the initial solution? (a) 4.67 (b) 5.08 (c) 8.31 (d) 8.92 (e) 9.33 26. (12 Points) What is the solubility of solid Cu(OH)2 (in units of grams of Cu(OH)2 per liter of solution) in an aqueous solution with 0.025 M NaOH? The Ksp of Cu(OH)2 is Ksp = 1.6 x 10-19. (a) 6.4 x 10-18 g Cu(OH)2 / Liter (b) 6.2 x 10-16 g Cu(OH)2 / Liter (c) 2.5 x 10-14 g Cu(OH)2 / Liter (d) 3.4 x 10-07 g Cu(OH)2 / Liter (e) 3.3 x 10-05 g Cu(OH)2 / Liter 11 27. (8 Points) What is the solubility product (Ksp) of CaF2 if 2.5 x 10-3 moles of solid CaF2 will dissolve in one liter of water? (a) 1.56 x 10-8 (b) 6.25 x 10-8 (c) 1.25 x 10-7 (d) 6.25 x 10-6 (e) 1.25 x 10-5 28. What is the version of your Final Exam? (a) Version A (b) Version B 12 13 ...
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This note was uploaded on 05/01/2008 for the course CHEN 1211 taught by Professor Gin,doug during the Fall '08 term at Colorado.
- Fall '08