Exam3 - CHEM 1307 Directions: 1. The only items you may...

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Unformatted text preview: CHEM 1307 Directions: 1. The only items you may have on your desk are: a scientific calculator, #2 pencils, and an eraser. All other material must be left in the front of the room. 2. On your answer sheet in the space marked “NAME,” PRINT your name; in the space marked “SUBJECT”, print your course and section number. In the space marked “ID NUMBER,” fili in your Raider ID {R number) in the blank spaces starting on the left and bubble—in the corresponding numbers AND THE R below the blanks. Be sure to fill in your test version. Make dark marks on the answer sheets, not dashes. Erase completely if you change answers. 3. Put all scratch work on the exam pages. Do not put any extra marks on the answer sheet. You may keep the exam! 4. The exam consists of IO multiple-choice questions. Choose the w best or correct answer for each question. Mark your choice on both the answer sheet and the exam paper. 5. You are to use only the answer sheet that is provided with the exam. Do not use any other answer sheet. The score that you receive for the exam will be the score on the answer sheet that you turn in and will not be changed for any reason. 6. Cell phones must be turned off and out of sight during exams. No PDA‘s or MP3 players allowed. 7. The periodic table, censtants, and useful equations are provided below. m iatm: 101325 Pa R=0.08206 :33145 Kmol Kmol h = 6.626 x 104415 c : 2.993 x 108 m/s _1 D : 3.34 x 10‘3°Cm RH=2.18x10"8.J 1ca1:4.184r e‘=1.60x10""c n 2 1.0974 x 107 m'] F = 96458 C/mol Periodic Table of the Elements 1 18 114 H 1.008 3 6.941 . 11 Na Mg 22.99 24.31 19 20 Ca 39113 4008 . . . . . . . . . . . . . . 37 38 41 R Sr Y Zr Nb Me To Ru Rh Pd Ag Cd In Sn Sh Te 1 85 B7162 88.91 91.22 92.91 95.94 (98) 101.1 102.9 106.4 107.9 . . . . . b .4? 55 56 57 72 73 Y4 7’5 76 7'? F8 1’9 Cs Ba La Hf Ta W Re 05 1r 132.9 137.3 138.9 . . , . . . . . 87 88 89 Fr 1223) (226) (227} a. 8. a. What is the hybridization ofthe central atom in 11:5? sp b. sp2 c. sp3 (1. sp3d e. sp3d2 How many sigma (o) and pi (1:) bonds are in NQHZ‘? four 0, zero TC b. four 5, one 7: c. three (5, zero E d. three (5. one a e. three 0, two 71: What is the molecular geometry around a central atom that is sold hybridized and has two lone pairs of electrons? trigonalbipyramidal b. trigonal planar c. T-shaped d. seesaw e. octahedral One product of the combustion of ethylene (CQHJ) is carbon dioxide. What change in hybridization of the carbon atom occurs in this reaction? SP3 to sp2 b. sp3 to 5p 6. sz to Sp3 (1. 5102 to sp3d2 e. Sp2 to 5}) A 2.48 L sample of He at 739 mm Hg is mixed with 6.08 L ofAr at 325 mm Hg both at 25 °C. The gases are then placed in a 4.80 L container at 25 °C. What is the total pressure (mm Hg)? 380 mm Hg b. 412 mm Hg 0. 522 mm Hg d. 625 mm Hg e. 793 mm Hg What is the density (g/L) ofBrF; at 425 mm Hg and 77 0C? 0.92 g/L b. 2.66 g/L c. 1.21 g/L d. 1.72 g/L e. 3.05 g/L What volume (L) of 03 gas at 745 mm Hg and 21 CC will be released from the reaction of 24.5 g of Xer with water? 2 xer2 (s) + 2 H20 (1) —~m—> 2 Xe (g) + 02 (g) + 4 HF (g) 3.57L b. 1.78L c. 7.14L d. 1.27L e. 4.63L A 2.00 L sample of air at -50 0C has a pressure of 700 mm Hg. What will be the new pressure (mm Hg) ifthe temperature is raised to 50 DC and the volume is increased to 4.00 L? 507 mm Hg b. 410 mm Hg c. 247 mm Hg d. 552mm Hg e. 700 mm Hg R : 0.0821 Latm/molK Please use the following molecular orbital diagram to answer questions 9-10. For oxygen and fluorine, the 03p orbital should be lower in energy than the ngp. Use core and valence electrons. * T —_ 02v 75*2p 02p TEgp 0$25 025 0*IS Gls Energy 9. Compare Ff, F2 and F21 Order the compounds from weakest to strongest bonds. 3. F27<F3<F3+ F2+< F3 (F37 C. F2L<F37<F3 F2‘<F2_<F2 e. F2 <F2_<F2+ l0. What is the bond order in OF? CHEM 1307 Exam 3 April 20, 2011 Version B Directions: 1. The only items you may have on your desk are: a scientific calculator, #2 pencils and an eraser. All other material must be left in the front of the room. 2. On your answer sheet in the space marked “NAME,” PRINT your name; in the space marked “SUBJECT”, print your course and section number. In the space marked “ID NUMBER,” fill in your Raider [D (R number) in the blank spaces starting on the left and bubble-in the corresponding numbers AND THE R below the blanks. Be sure to fill in your test version. Make dark marks on the answer sheets, not dashes. Erase completely if you change answers. 3. Put all scratch work on the exam pages. Do not put any extra marks on the anSWer sheet. You may keep the exam! 4. The exam consists of 30 multiple-choice questions. Choose the one best or correct answer for each question. Mark your choice on both the answer sheet and the exam paper. 5. You are to use only the answer sheet that is provided with the exam. Do not use any other answer sheet. The score that you receive for the exam will he the score on the answer sheet that you turn in and will not be changed for any reason. 6. Cell phones must be turned off and out of sight during exams. No PDA’s or MP3 players allowed. 7. The periodic table, constants, and useful equations are provided below. You must remain seated until at least 7:30 pm. m 1 atm = 760 mm Hg = 760 torr R = 0.08206 = 8.3145 Kmol Kmol gBRT y u = 1— N} Mfr! rate of effusion of gas A = mm = time of effusion of gas 8 rate of effusion of gas B \JMMA time of effusion of gas A Periodic Table of the Elements 1 18 1A 8A 13‘ 14 15 16 17 1 H 2 .006 2A 6A 7A 4.003 3 4 5 6 7 5 9 10 6.941 9.012 10.81 12.01 14.01 16.00 19.00 20.19 11 12 13 14 15 16 17 18 Na Mg 3 4 5 6 7 8 9 10 1'1 12 Si Cl 22.99 24.31 38 4B 58 SB 78 813 SB 58 18 25 26.98 28.09 30.97 32.07 35.45 39.95 19 20 21 22 23 24 25 25 27 28 29 30 31 32 33 34 35 36 K C: St: Tl V Cr Fe Ga 5: Br 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 72.59 74.92 78.96 79.90 83.80 85.47 87.82 88.91 91.22 92.91 95.94 (98) 101.1 102.9 106.4 107.9 112.4 114.8 118.7 121.8 127.6 126.9 131.3 55 55 57 72 73 74 75 76 77 78 79 90 81 82 83 84 85 35 mmumnwmwnlnnnnnnnn 132.9 137.3 138.9 178.5 180.9 183.8 186.2 190.2 192.2 195.1 197.0 200.6 204.4 207.2 209.0 (210) (210) (222) 87 88 99 104 105 105 107 108 109 Fr Fla Ac Unq Unp Unh Uni Uno Una (223) (225) (227) (257) (260) (263) (262) (265) (266) 58 59 60 61 52 63 64 65 66 67 58 69 70 71 Ce Pr Nd Pm Eu Gd Dy Tm Yb Lu 140.1 140.9 144.2 (147) 150.4 152.0 157.3 158.9 162.5 164.9 157.3 168.9 173.0 175 90 91 92 93 94 95 96 97 93 99 100 101 102 103 w~uw~nnnnannnm 232.0 (231) 238.0 (237) (242) (243) (247) (247) (249) (254) (253) (256) (254) (257) Estimate the enthalpy change for the following reaction using the bond dissociation enthalpies (BDE) provided in the table below. 2 H2 (9) + 02 (9) '9 2 H20 (9) Bond BDE lkJ/mol) H-H 436 0-H 463 0:0 498 a. -918 kJ b. -482 kJ c. +8.00 kJ d. +340 kJ e. -692 k] Hydrazine, N2H4, is a good reducing agent that has been used as a component in rocket fuels. Using the Lewis structure shown below, what is the idealized H-N-H bond angle? a. 60° in. 90° c. 109.5° d. 120° e. 180° 3. If 3.29 L of N0 gas at 124 °C and 0.869 atm are reacted with excess CO according to the balanced equation below, what volume of N2 gas will be produced at the same temperature and pressure? 2 (:0 (g) + 2 NO (9) -> 2 c0: (9) + N2 (9) a. 3.29 L b. 1.65 L c. 6.58 L d. 0.869 L e. 12.4 L 4. A 5.0 mol sample of gas at 1.0 atm is expanded at constant temperature from 10 L to 15 L. What is the final pressure? a. 0.67 atm b. 1.5 atm c. 3.3 atm d. 7.5 atm e. 15 atm 5. What is the hybridization of the central atom in PFS? 5p 5;)2 sp3 . sp3d sp3d2 {Dunne 6. What is the bond order for a species with the molecular orbital configuration (015)2(Gls*)2(523)2(525*)2(32p)4(520)2(n2p*)1? . 0.5 1 1.5 . 2 . 2.5 mung-m A 0.100 mol sample of magnesium metal and an excess of aqueous hydrochloric acid react according to the balanced equation below. How many liters of hydrogen gas, measured at ST P, are produced? Mg (5) + 2 HCI (aq) 9 M90; (aq) + H; (g) a. 2.24 L b. 4.48 L c. 5.60 L d. 11.2 L e. 22.4 L Calculate the root-mean-square speed of methane, CH4, at 78 °C. 23.4 m/s 350 m/s 550 m/s 667 m/s 740 'm/s EDP-PETS” A 0.850 mol sample of nitrous oxide, a gas used as an anesthetic by dentists, has a volume of 20.46 L at 123 °C. What would the volume be at 468 °C if the pressure is held constant? a. 5.38 L b. 10.9 L c. 19.0 L d. 38.3 L e. 77.9 L 10. Using the molecular orbital diagram provided below, counting both core and valence electrons, 82: Energy uszp Hflzp UZP Hzp — ("‘25 _— (5*15 has a bond order of 1 and is diamagnetic. has a bond order of 2 and is diamagnetic. has a bond order of 1 and is paramagnetic. has ‘a bond order of 2 and is paramagnetic. Has a bond order of 1.5 and is paramagnetic. 909.0527!» 11. In molecules, as bond order increases: a. both bond length and bond strength increase. b. both bond length and bond strength decrease. c. bond length increases and bond strength decreases. d. bond length decreases and bond strength increases. e. bond length is unchanged and bond strength increases. 12. Given the electronegativity values below, which is the most polar bond? Element B C N O F Electronegativity 2.0 2.5 3.0 3.5 4.0 13. Which of the following gases effuses most rapidly? nitrogen oxygen hydrogen chloride ammonia carbon monoxide EDP-PST!” 14. How many bonding pairs and how many lone pairs (respectively) are found around the central atom in Cle”? - --. - r090?!» WNyNH NUJHNLAJ I 15. The Mond process produces pure nickel via the thermal decomposition of nickel tetracarbonyl according to the balanced equation below. How many grams of nickel tetracarbonyl must react to form 255 L of CO at 0.989 atm and 295 K? Ni(CO)4 (l) 9 Ni (5) + 4 CO (9) a. 1780 g b. 45.8 g c. 255 g d. 697 g e. 444 g 16. What is the electron pair geometry of BrF5? octahedral square planar square pyramidal seesaw trigonal bipyramidal roe—0.65» 17. In which of the following does the central atom violate the octet rule? 03 N02 NH4+ C032- C52 $0510.69: 18. What is the hybridization of the central atom in NF3? 5p sp2 sp3 sp3d sp3d2 {De—p.091 19. A carbon dioxide sample weighing 44.0 g occupies 32.68 L at 65.0 °C at 645 torr. What is_ its volume at STP? 22.4 L 31.1 L 34.3 L 35.2 L 47.7 L 9390.69: 20. Which of the following molecules is non-polar (has no dipole moment)? a. H25 b. C52 C. CH2Cl2 d. PH3 e. CH20 21. A 10.3 L cylinder contains 10.7 moles of Clz gas at 21.2 °C. What is the pressure of the gas assuming ideal behavior? a. 34.2 atm b. 19.5 atm c. 25.1 atm d. 1.81 atm e. 3.08 atm 22. What is the molecular geometry of NHZCl as predicted by VSEPR theory? trigonal pyramidal tetrahedral T—shaped . seesaw trigonai planar younger 23. Which of the following is a polar molecule? Si H4 CH2Ci2 BCI3 SFs BEHZ {99-91391 24. Which of the following statements relating to molecular orbital (M0) theory is incorrect? a. The combination of two atomic orbitals produces one bonding and one antibonding molecular orbital. b. A bonding molecular orbital is lower in energy than the two atomic orbitals from which it is formed. c. The combination of porbitals may resuit in either 0' or 7: molecular orbitals. d. A species with a bond order of zero will not be stable. e. In a stable molecule having an even number of electrons, all electrons must be paired. 25. Draw the Lewis structure for H3CCN. How many sigma and pi bonds are found in the structure? 45,17: 50,27: 50,11t 66,1n 76,07! ED219537!” 26. A flask with a volume of 3.16 L contains 9.33 g of an unknown gas at 32.0 °C and 1.00 atm. What is the molar mass of the gas? a. 7.76 g/mol b. 66.1 g/mol c. 74.0 g/mol d. 81.4 g/mol e. 144 g/mol 27. Which of the following compounds displays resonance? a. CH4 b. XEFz C. 03 d. NH3 e. BeCIz 28. If the rate of effusion of C02 through a porous barrier is 8.54 x 10'4 moi/hr, what is the rate of effusion of Kr gas under the same conditions? a. 6.19 x 10“ moI/hr b. 4.48 x 1044 moi/hr c. 1.63 x 10'3 moI/hr d. 1.18 x 10-3 moi/hr e. 7.22 x 104 moi/hr 29. A 12.0 L flask at 308 K contains 12.4 9 Ar and 16.2 9 N2 with a total pressure of 30. 1.69 atm. What is the partial pressure of Ar? a. 1.10 atm Ar b. 0.589 atm Ar c. 0.732 atm Ar (:1. 0.980 atm Ar e. 1.29 atm Ar From left to right, assign the formal charges for the Lewis structure shown below. -1, +2, -1 0, -1, +1 0, +1, -1 0, 0, -1 0, 0, 0 EDP-9579’ ...
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Exam3 - CHEM 1307 Directions: 1. The only items you may...

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