Chemistry 1210, Section 3, Fall semester 2012 Second Hour Exam October 24, 2012 Dr. Scott Ensign ExamVersion 0001

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1 Chemistry 1210, Section 3, Fall semester 2012 Second Hour Exam October 24, 2012 Dr. Scott Ensign ExamVersion 0001 Instructions: Be sure to mark the exam version number (0001) on your scantron Do not begin until 10:30 AM. The exam must be turned in by 11:20 AM This exam should have 25 questions. Each question is worth 4 points for a total of 100 points. A periodic table and an exam information sheet should be on the next two pages. Please show a copy of a picture ID (USU card or drivers license) when turning in your exam to one of the exam proctors. Use only a #2 Pencil to mark the best answer on the ScanTron Sheet. Be sure to provide your LAST NAME, STUDENT NUMBER, and exam version number on the scantron. You will turn in only the Scantron sheet. You should keep the rest of the exam. Please present your student activity card or other form of identification when turning in the exam. Be very careful filling in the scantron bubbles (last name, A number, and answers) correctly: The scantron is what gets turned in and graded, not the exam. Please do not spend too much time on any one problem. If you get stuck, move on to an easier problem, and come back to the harder one later. Good luck!

2 1. Consider the following hypothetical reaction: A + B C kj This reaction is (i) and the direction of heat flow is (ii). a. (i) endothermic; (ii) from the system to the surroundings b. (i) exothermic; (ii) from the surroundings to the system c. (i) endothermic; (ii) from the surroundings to the system d. (i) exothermic; (ii) from the system to the surroundings 2 2. Calculate the change in internal energy of the system for a chemical reaction in which 10.0 kj of heat is absorbed while the system performs 20.0 kj of work on the surroundings. a kj b kj c kj d kj 3. Enthalpy is the heat of a reaction under what conditions? a. (a) constant volume b. (b) constant pressure c. (c) constant temperature d. both (a) and (b) e. all of the above 4. Sodium metal reacts with chlorine gas according to the following balanced chemical equation: 2Na(s) + Cl 2 (g) 2NaCl(s) ΔH = kj What is the enthalpy change when 25.0 grams of NaCl are produced in the reaction? Assume the reaction is performed at constant pressure. a x 10 3 kj b kj c kj d kj e kj 5. Given the data below, determine ΔH for the reaction: S (s) + O 2(g) SO 2(g) 2SO 2(g) + O 2(g) 2SO 3(g) H = -196 kj 2S (s) + 3O 2(g) 2SO 3 (g) H = -790 kj a kj b kj ` c kj d kj e kj

3 6. When solid calcium oxide dissolves in water, the following exothermic reaction occurs: 3 CaO(s) + H 2 O(l) Ca(OH) 2 (aq) ΔH =? kj When mol of CaO is dissolved in water in a calorimeter to produce a total solution volume of 75.0 ml, the temperature increases from C to C. Use this information to determine the enthalpy change for the reaction in units of kj/mol of reaction. Assume the specific heat of the solution is the same as that of pure water (4.18 J/g C ) and that the density of the solution is 1.00 g/ml. a kj b kj c kj d kj e kj 7. Use the information in the table below to calculate H for the reaction of nitric oxide (NO) with oxygen to produce nitrogen dioxide, a component of smog: 2NO(g) + O 2 (g) 2NO 2 (g) a kj/mol b kj/mol c kj/mol d kj/mol e kj/mol 8. According to the first law of thermodynamics: a. the energy of the universe is constant b. enthalpy is a state function c. internal energy is a state function d. the energy of the surroundings increases for any chemical reaction e. both (a) and (d) are correct 9. For radiant energy, a shorter wavelength is associated with a (i) frequency and (ii) energy. a. (i) lower; (ii) higher b. (i) higher; (ii) lower c. (i) higher; (ii) higher d. (i) lower; (ii) lower

4 4 10. A typical microwave oven generates microwave radiation with a frequency of 2450 MHz, which has just the right energy to excite the bonds in water molecules, generating heat. What is the wavelength of these microwaves? a. 8.2 m b. 1.2 x m c m d. 1.2 x 10 5 m e. 7.4 x 10 5 m 11. It takes 2221 kj of energy to synthesize one mol of sucrose. How many photons of light with a wavelength of nm would a plant have to absorb to provide this amount of energy? a x b x c x d x e x For the 3p x orbital, the p specifies the orbital s (i) while the x specifies the orbital s (ii) : a. (i) size; (ii) shape b. (i) spatial orientation; (ii) shape c. (i) shape; (iii) electron spin d. (i) shape; (ii) spatial orientation e. (i) energy; (ii) shape 13. The phenomenom of line spectra led to the proposal that (i) while the photoelectric effect led to the proposal that (ii) : a. (i) radiant energy is quantized; (ii) energy has particle like properties b. (i) electronic transitions always release visible light; (ii) energy has particle like properties c. (i) energy states of the electron are quantized; (ii) energy has particle like properties d. (i) radiant energy is quantized; (ii) matter has wavelike properties e. (i) energy states of the electron are quantized; (ii) radiant energy is quantized 14. How much energy is required to promote an electron in the hydrogen atom from the n = 3 state to the n = 8 state? a x J b x J c x J d x J e x J

5 15. How many electrons may reside in the (i) n = 3 and (ii) n = 4 shells? a. (i) 9 (ii) 16 b. (i) 4 (ii) 9 c. (i) 18 (ii) 32 d. (i) 16 (ii) 32 e. (i) 6 (ii) For the following orbital drawings, identify which represent violations of Hund s rule and the Pauli Exclusion principle. 17. According to Schrodinger s quantum mechanical model of the atom: a. Electrons within atoms reside in orbitals, which are probability functions describing the location of an electron in 3-dimensional space b. The behavior of an electron in an atom is better described by considering the electron as a wave function rather than as a particle in motion c. Atomic orbitals may have nodes which are areas in space where there is no probability of finding an electron d. both (a) and (b) are correct descriptions of the quantum mechanical model of the atom e. (a) (b, and (c) are all correct descriptions of the quantum mechanical model of the atom 18. Write the electron configuration for the precious metal Platinum (Pt), abbreviating with the appropriate noble-gas inner core. a. [Xe]6s 2 4f 14 5d 8 b. [Xe]6s 2 5f 14 5d 8 c. [Xe]6s 2 4f 14 4d 8 d. [Xe]6s 2 6f 14 6d 8 e. [Xe]6s 2 5f 14 6d Suppose all of the following objects are moving at a velocity of 1.0 x 10 6 m/s. Which has the longest debroglie wavelength? a. a proton b. a neutron c. an electron d. an alpha particle (helium nucleus) e. they all of the same de Broglie wavelength

6 6 20. Use the simplified model for electronic structure where all electrons of a given n value are assumed to have the same average energies and to reside the same distance from the nucleus in answering this question: What is the effective nuclear charge felt by an electron in the n = 2 shell of sulfur? a. +16 b. +14 c. +8 d. +6 e Two elements in groups 1A to 7A of n = 2 have positive electron affinities. Predict which elements they are based on your knowledge of electronic properties. a. Be, B b. B, O c. Be, N d. B, O e. Be, O 22. The general trends observed for how first ionization energies change within a group can be explained by (i). The general trends observed for how first ionization energies change within a period can be explained by (i). a. (i) principal quantum number of the ionizable electron; (ii) population of different subshells within an energy level b. (i) population of different subshells within an energy level; (ii) principal quantum number of the ionizable electron c. (i) principal quantum number of the ionizable electron; (ii) effective nuclear charge felt by the ionizable electron d. (i) effective nuclear charge felt by the ionizable electron; (ii) principal quantum number of the ionizable electron e. (i) population of different subshells within an energy level; (ii) effective nuclear charge felt by the ionizable electron 23. Which atom would have a second-ionization energy very much greater than the first-ionization energy? a. Na b. Mg c. Al d. Si 24. For which of the following atoms are electron(s) in the 3s orbital closest to the nucleus? a. Na b. Mg c. Al d. Si e. they are all the same distance from the nucleus 25. Which of the following would you predict would have the most negative electron affinity? a. Na b. Li c. Be d. S e. Ar