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University Tufts Chem 1 Summer 2008 Practice Exam 2a I. Multiple Choice Questions A Only one answer is assumed correct in each question. 1. All of the following are state functions except A) q B) T C) U D) H 2. Which of the following is a correct statement of the First Law of Thermodynamics? A) The internal energy of a system that does not exchange energy with the surroundings is constant. B) The internal energy of a system can be changed only by heat transfer and work and E = w + q C) The internal energy of the Universe is constant D) All of the above E) None of the above 3. Which of the following chemical equations is used to define the standard enthalpy of formation of ammonium perchlorate? A) N2(g) + Cl2(g) + 2O2(g) + 2H2(g) NH4ClO4(s) B) N2(g) + Cl2(g) + 4O2(g) + 4H2(g) 2NH4ClO4(s) C) NH3(g) + HClO4(l) NH4ClO4(s) D) All of the above E) None of the above 4. Which of the following describe a standard state at 25oC? A) Hydrogen gas (H2) at a pressure of 1 atm B) Pure liquid water C) 1 M HClO4(aq) D) All of the above E) None of the above 5. Which of the following experiments most directly supports de Broglie's hypothesis of the wave nature of matter? A) blackbody radiation B) the photoelectric effect C) alpha-particle scattering by a metal foil D) electron diffraction by a crystal E) the emission spectrum of the hydrogen atom 6. Estimate the wavelength of the wave below. A) 3 nm B) 0.5 nm C) 1 nm D) 1.5 nm E) 2 nm 7. How many nodes are present in a 3s and a 3d orbital, respectively? A) 2 and 2 B) 3 and 3 C) 0 and 2 D) 1 and 1 E) 2 and 3 8. The total number of orbitals in a shell with principal quantum number 4 is A) 32. B) 50. C) 4. D) 40. E) 16. 9. Which of the following has the smallest atomic radius? A) Cl B) P C) S D) Si E) Al 10. Arrange the following types of photons of electromagnetic radiation in order of decreasing energy: red light, radio, x-rays, -rays, infrared. A) -rays > x-rays > red light > infrared > radio B) radio > red light > infrared > x-rays > -rays C) x-rays > red light > infrared > -rays > radio D) x-rays > -rays > red light > infrared > radio E) -rays > x-rays > radio > infrared > red light 11. Which of the following atoms has the most unpaired electrons? A) Ne B) Na C) Nb D) Ni 12. Which set of quantum numbers could correspond to a 4f orbital? D) n = 3, l = 2, ml = +1 A) n = 4, l = 4, ml = +3 B) n = 4, l = 3, ml = +4 E) n = 3, l = 2, ml = 0 C) n = 4, l = 3, ml = -3 13. Which of the following has the most negative electron affinity? A) Cl B) C C) Mg D) Ba E) Ne 14. Which of the following has the lowest lattice enthalpy? A) NaCl B) AlN C) MgS D) Ba3N2 E) NaBr 15. Which of the following has the smallest ionic radius? A) Ti2+ B) Ti3+ C) Ti4+ D) Zr4+ 2 16. All of the following elements exist as diatomic gases at room temperature and atmospheric pressure except A) H B) Ar C) N D) Cl E) O 17. Which of the following species does not obey the octet rule? A) NH3 B) NH4+ C) NH2 D) CO E) CO2 18. Which of the following statements is true? A) Atoms with high ionization energies have large atomic radii. B) Atoms with high ionization energies usually have high electronegativities. C) Atoms with high ionization energies usually have low electron affinities. D) Atoms with high ionization energies tend to form cations. E) Atoms with high ionization energies tend to form metallic bonds. 19. Which of the following compounds has bonds with the most ionic character? A) SiO2 B) P4S10 C) P4O10 D) CO2 E) NO2 20. Which of the following substances would conduct electricity well in the solid state? A) SnO2 B) SO3 C) S8 D) Sc E) Se 21. An element E has the electronic configuration 1s22s22p5. What is the formula of its compound with lithium? A) LiE2 B) LiE C) Li2E D) Li3E D) Li4E 22. Which of the following metals has the most pronounced metal character? A) Be B) Sr C) Li D) Rb 23. Which of the following is true? A) A 2s orbital has two nodal surfaces. B) An electron in a d-orbital has zero probability of being found at the nucleus. C) An f-orbital has a spherical boundary surface. D) s-orbital An becomes denser as the distance from the nucleus increases. E) An electron in an s-orbital has a zero probability of being found at the nucleus. 24. Which of the following will make an acidic solution in water? A) P2O3 B) SrO C) LiOH D) NaCl 25. Which of the following elements is liquid at room temperature? A) N2 B) Mg C) Al D) Br2 E) Xe 3 II. Multiple Choice Questions B 1. The enthalpy of vaporization of water is +40.7 kJ mol-1 and the enthalpy of freezing of water is -6.0 kJ mol-1. What is the enthalpy of condensation of water vapor? A) -6.0 kJ mol-1 B) -34.7 kJ mol-1 C) -40.7 kJ mol-1 D) -46.7 kJ mol-1 2. A battery does 35 kJ of work driving an electric motor and heat in the amount of 7 kJ is released from the battery. What is the change in internal energy of the battery? A) -35 kJ B) +42 kJ C) -42 kJ D) -28 kJ E) +28 kJ 3. In 1.0 s, a 60 W bulb emits 11 J of energy in the form of infrared radiation (heat) of average wavelength 1850 nm. How many photons of infrared radiation does the lamp generate in 1.0 s? A) 1.0 1029 B) 1.0 1020 C) 6.8 10-14 D) 1.1 10-19 E) 6.6 1023 4. You are caught in a radar trap and hope to show that the speed measured by the radar gun is in error due to the uncertainty principle. If you assume that the uncertainty in your position is 2.5 m, and that the car has a mass of 2150 kg, what is the approximate uncertainty in the velocity? A) 1 10-33 ms-1 D) 1 1038 ms-1 B) 1 10-19 ms-1 E) 1 10-38 ms-1 33 -1 C) 1 10 ms 5. Calculate the velocity of an oxygen molecule if it has a de Broglie wavelength of 0.0140 nm. A) 890. ms-1 D) 445 ms-1 8 -1 B) 3.00 10 ms E) 8.90 ms-1 C) 1780 ms-1 4 III. Enthalpies of Reactions a) Calculate the enthalpy of reaction H2Te(g) + 2 O2 (g) + 2H2O(l) H6TeO6(aq) from the following data. H2Te(g) + 4H2O2(aq) H6TeO6(aq) + 2H2O(l), Hor = -1445 kJ/mol H2(g) + O2 (g) H2O(l), Hor = -286 kJ/mol H2(g) + O2(g) H2O2(aq), Hor = -191 kJ/mol b) (5 pts) Using tabulated data, calculate the enthalpy of the following reaction: Fe3O4(s) + 8H+(aq) Fe2+(aq) + 2Fe3+(aq) + 4H2O(l) IV. Electron Configurations Using the noble gas core notation write out the electron configurations for the following: a) C b) Mn3+ c) Th d) Se2e) Which atom or ions has most unpaired electrons? 5 V. Lewis structures A. Each of the molecules below can form a stable Lewis structure that obeys the octet rule and has zero formal charges. Draw such a structure. 1. CH3NH2 2. H2S 3. CH3COOH 4. As2O3 B. For each of the ions or molecules below, draw the octet Lewis structure with minimum formal charges. Show the formal charges. 1. CN2. PO3F2- 3. NH4+ 4. HBrO3 6 VI. A. Guanidinium Chemical Bonding a) Draw the resonance octet Lewis structures for the guanidinum cation [C(NH2)3]+ b) Calculate the average C-N bond order. B. Dioxygen species a) Draw the octet Lewis structures for: i) oxygen molecule, O2 ii) peroxide anion, O22- b) Which one has a stronger O-O bond? C. Types of Bonding Classify bonding in the following elements, alloys, and compounds as ionic, covalent, or metallic. Li(s) Li3Al(s) H2(g) LiH(s) 7 VII. Assorted Problems A. a) Write the formula of calcium sulfate. b) What types of chemical bonding is present in the compound? Illustrate your answer with appropriate Lewis structure(s). c) Is calcium sulfate solid, liquid, or gas at room temperature? B. Identify possible and impossible combinations of quantum numbers: a) n = 11 l=0 ml = 0 ms = ms = - ms = ms = 0 b) n = 0 l = 0 ml = 0 c) n = 2 l = 1 ml = -1 d) n = 3 l = 0 ml = C. Consider an orbital with the quantum numbers n = 2 and l = 1. a) Name the orbital. b) Which nodes does such an orbital have? c) Sketch such an orbital. 8 VIII. Energy balance Hydrogen atom with the electron in an orbital with n = 3 absorbs a quantum of electromagnetic radiation with the frequency 5.00 1015 Hz. Calculate the speed of a fastmoving electron generated if the hydrogen nucleus remains still. 9

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