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Unformatted text preview: Chemistry 1211 Prof. Dan Schwartz Exam #2 Thursday, 3/13/2003 7:00 8:30 P.M. There is a single correct choice for each question. Answer all questions on the Scantron sheet by filling in the proper bubble with a #2 pencil. If you change an answer, erase the undesired mark thoroughly. Be sure to fill in the boxes for your student number, name and lab section; then correctly fill in the corresponding bubbles beneath them. A periodic table and other useful information are attached to the back of the exam. There are 4 exam pages and 26 questions. Check to be sure you have answered them all! 1. (zero points) Which version of the exam do you have? (a) A (b) B 2. (5 points) Which two ions have the same electron configuration in the ground state? (a) Rb+ and Cs+ (b) Ba2+ and I (c) Se2 and I (d) Fe2+ and Fe3+ 3. (5 points) List the elements Na, Ca, Rb, Cl, He in order of decreasing first ionization energy. (a) He > Cl > Ca > Na > Rb (b) He > Na > Ca > Cl > Rb (c) He > Na > Cl > Ca > Rb (d) Rb > Ca > Cl > Na > He 4. (5 points) Which ionic compound would be expected to have the highest lattice energy? (a) NaCl (b) MgO (c) AlF3 (d) Al2O3 5. (5 points) Which element, indicated by letter on the periodic table below, has a 2+ ion with electron configuration [Ar]3d10 ? (a) A (b) B (c) C (d) D Exam #2 Page 1 6. (5 points) Element A has an electronegativity of 0.8 and element B has an electronegativity of 3.0. Which statement best describes the bonding in A3B? (a) The AB bond is largely covalent with a d charge on A. (b) The AB bond is largely covalent with a d+ charge on A. (c) The AB bond is largely ionic with A as the cation. (d) The AB bond is largely ionic with A as the anion. 7. (5 points) Which is the most acceptable electron dot structure for N2H2? .. .. (a) H--N--N--H .. .. .. .. (b) H--N N--H (c) H--N N--H .. .. (d) H--N N--H 8. (5 points) Given that the electronegativity is 2.5 for both C and S, which is the best electron dot structure for SCN based on formal charge? .. .. (a) [ : N C S :] .. (b) [ : N C S :] .. .. .. (c) [ : N S C :] .. (d) [ : N C S :] .. 9. (5 points) The following ball-and-stick molecular model is a representation of the amino acid alanine. Unshaded spheres = H. Choose the answer that best fills in the blanks in the following sentence: The carbon atom labeled C2 has a hybridization of hybridization of . (a) sp, sp2 (b) sp2, sp3 (c) sp3, sp2 (d) sp3, sp and the carbon atom labeled C3 has a Exam #2 Page 2 10. (5 points) What is the shape of AsCl3? (a) T-shaped (b) tetrahedral (c) trigonal planar (d) trigonal pyramidal 11. (5 points) Which of the following is NOT a state function? (a) altitude (b) heat (c) internal energy (d) entropy 12. (5 points) For the reaction (a) DH0vap = 62.4 kJ/mol (b) DH0vap = 62.4 kJ/mol (c) DH0sub = 62.4 kJ/mol (d) DH0sub = 62.4 kJ/mol I2(g) I2(s) , DH0 = 62.4 kJ at 25 C. Based on these data, at 25 C 13. (5 points) When 1.50 g of Ba metal is added to 100. g of water in a container open to the atmosphere, the reaction Ba (s) + 2 H2O (l) Ba(OH)2 (aq) + H2 (g) occurs and the temperature of the water rises from 22.0 C to 33.1 C. Given that the specific heat of water is 4.18 J/(gC), find DH for the reaction. (a) 425 kJ (b) 3.09 kJ (c) 3.09 kJ (d) 425 kJ 14. (5 points) Find DH for the reaction BaCO3 (s) BaO (s) + CO2 (g) given 2 Ba (s) + O2 (g) 2 BaO (s) Ba (s) + CO2 (g) + 1/2 O2 (g) BaCO3 (g) (a) 1929.5 kJ (b) 1376.0 kJ (c) 284 kJ DH = 1107.0 kJ DH = 822.5 kJ (d) 269.0 kJ 15. (5 points) The figure below represents the spontaneous evaporation of isopropyl alcohol, (CH3)2CHOH. What are the signs ( + or ) of DH, DS, and DG for this process? (a) (b) (c) (d) DH = +, DS = +, DG = + DH = +, DS = +, DG = DH = , DS = , DG = + DH = , DS = , DG = Exam #2 Page 3 16. (5 points) A basketball is inflated to a pressure of 1.50 atm in a 20.0 C garage. What is the pressure of the basketball outside where the temperature is 5.00 C? (a) 0.375 atm (b) 1.37 atm (c) 1.42 atm (d) 1.67 atm 17. (5 points) Which of the following gases would have a density of 1.21 g/L at 7.0 C and 0.987 atm? (a) Ar (b) N2 (c) Ne (d) O2 18. (5 points) A balloon contains 0.76 mol N2, 0.18 mol O2, 0.031 mol He, and 0.026 mol H2 at 739 mm Hg and 22 C. What is the partial pressure of O2? (a) 19 mm Hg (b) 23 mm Hg (c) 130 mm Hg (d) 560 mm Hg 19. (5 points) Excess XeF6 reacts with 2.46 atm of hydrogen gas at 45 C in a 0.579 L container by the reaction XeF6 (s) + 3 H2 (g) Xe (g) + 6 HF (g) Assuming the temperature does not change, what is the pressure in the container after the reaction is complete? (a) 0.82 atm (b) 4.92 atm (c) 5.74 atm (d) 8.20 atm 20. (5 points) You are given two flasks of equal volume. One contains H2 gas at 0 C and 1 atm while the other contains CO2 gas at 0 C and 2 atm. Which of the following quantities will be the same for both flasks? (a) average molecular kinetic energy (b) average molecular speed (c) density (d) number of molecules present 21. (5 points) Rank the following substances in order of increasing DHvap. KCl, HCl, NH3, CH4, H3CCH3 (a) (b) (c) (d) CH4 < H3CCH3 < KCl < HCl < NH3 H3CCH3 < CH4 < NH3 < HCl < KCl CH4 < H3CCH3 < HCl < NH3 < KCl KCl < HCl < NH3 < CH4 < H3CCH3 22. (5 points) As a liquid evaporates at a temperature below its boiling point, the temperature of the liquid (a) decreases. (b) decreases at low temperatures, but increases at high temperatures. (c) increases. (d) remains unchanged. Exam #2 Page 4 23. (5 points) While mercury is very useful in barometers, mercury vapor is toxic. Given that mercury has a DHvap of 56.9 kJ/mol and its normal boiling point is 356.7 C, calculate the vapor pressure in mm Hg at room temperature, 25 C. (a) 4.29 x 103 mm Hg (b) 2.36 mm Hg (c) 62.8 mm Hg (d) 751 mm Hg 24. (5 points) Considering the phase diagram below, which of the following statements is FALSE? (a) (b) (c) (d) Sublimation can occur only at pressures less than 0.5 atm. Solid and vapor phases coexist in equilibrium along the line CB. The normal boiling point of this substance is approximately 280 C. The solid phase of this material is more dense than the liquid phase. 25. (5 points) Considering the unit cell below, with oxygen atoms placed along cube edges and niobium atoms centered in each face of the cube, what is the correct formula of this compound? (a) NbO2 (b) NbO (c) Nb2O (d) Nb6O12 26. (5 EXTRA CREDIT points) What molecule is represented by the structural diagram below? (a) ethanol (b) toluene (c) propane (d) hexane Exam #2 Page 5 Answers: 1. a 2. b 3. a 4. d 5. c 6. c 7. b 8. a 9. c 10. d 11. b 12. d 13. a 14. d 15. b 16. b 17. b 18. c 19. c 20. a 21. c 22. a 23. a 24. b 25. b 26. d Exam #2 Page 6 ...
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This note was uploaded on 02/12/2011 for the course CHEM 112 taught by Professor Sttaf during the Spring '03 term at Arkansas Pine Bluff.
- Spring '03