Test2-2010-solutions

Test2-2010-solutions - CHEMISTRY 1E03 12 NOVEMBER 2010...

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Version 1 Page 1 CHEMISTRY 1E03 12 NOVEMBER 2010 Instructor: J. Barbier MCMASTER UNIVERSITY - TERM TEST # 2 - DURATION: 120 minutes Answers for Version 1 QUESTIONS 1–25 ARE WORTH 2 MARKS EACH. 1. Select the set of quantum numbers ( n, l, m l , m s ) that correctly describes one of the highest- energy electrons in the ground state of indium (In) . A) 5 ,0, 0, +½ B) 5, 2, 1, +½ C) 5, 2, -1, -½ D) 5, 1, 2, +½ E) 5, 1, 0, -½ 2 m The electron configuration of indium is [Kr] 5s 2 4d 10 5p 1 2. Use a Born-Haber cycle to calculate the lattice energy of NaBr(s) from the data below. (Note that bromine is liquid in its standard state.) nthalpy of sublimation of Na(s) = +177.8 kJ/mol First ionization energy of Na = +495.9 kJ/mol Bond energy (Br Br) = +192.5 kJ/mol Electron affinity of Br = 325 kJ/mol Enthalpy of formation of NaBr(s) = 361.1 kJ/mol Enthalpy of vaporization of Br 2 (l) = +30.9 kJ/mol A) 821 kJ/mol 2 m B) 450 kJ/mol C) 1456 kJ/mol D) 709 kJ/mol E) 806 kJ/mol 1 m Na(s) + ½ Br 2 (l) NaBr(s) H f (NaBr) = H subl (Na) + ½ H vap (Br 2 ) + ½ BE(Br 2 ) + H ion (Na) + H ea (Br) + H latt (NaBr)
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Version 1 Page 2 3. Consider the following reaction at equilibrium: 2 SO 2 (g) + O 2 (g) 2 SO 3 (g), with rxn = 198 kJ/mol. If the volume of the system is decreased at constant temperature, what change will occur in the position of the equilibrium? A) No change B) A shift will occur in the endothermic direction C) A shift to produce more O 2 D) A shift to produce more SO 2 E) A shift to produce more SO 3 2 m Le Chatelier’s principle. 4. Which one of the following molecules has a zero molecular dipole moment ? A) XeF 4 2m B) SF 4 C) CH 2 Cl 2 D) CO E) SO 2 XeF 4 is an AX 4 E 2 VSEPR type with a symmetrical square planar shape. 5. An Fe 2+ cation in its ground-state has ___ unpaired electrons and is _____. A) 3, diamagnetic B) 4, paramagnetic 2 m C) 5, diamagnetic D) 4, diamagnetic 1.5 m E) 3, paramagnetic The electron configuration of Fe 2+ is [Ar] 3d 6 4s 0
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Version 1 Page 3 6. Hydrogen sulfide is partially ionized in water as shown in the following reactions. What is the value of K 2 ? H 2 S( g ) + 2 H 2 O 2 H 3 O + ( aq ) + S 2 ( aq ) K 3 = 1.3 10 20 H 2 S( g ) + H 2 O H 3 O + ( aq ) + HS ( aq ) K 1 = 1.0 10 7 HS ( aq ) + H 2 O H 3 O + ( aq ) + S 2 ( aq ) K 2 = ? A) 7.7 10 26 B) 1.3 10 -13 2 m C) 1.3 10 -27 0.5 m D) 2.3 10 -7 E) 7.7 10 12 K 3 = [H 3 O + ] 2 [S 2- ]/[H 2 S] = K 1 K 2 7. Choose the false statement among the following: A) The reaction between NaOH(aq) and HNO 3 (aq) is exothermic. B)
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Test2-2010-solutions - CHEMISTRY 1E03 12 NOVEMBER 2010...

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