CHEM 101 Fall 09 Final Exam (a)

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1 CHEM 101 Fall 09 Final Exam (a) On the answer sheet (scantron) write your name, student ID number, and recitation section number. Choose the best (most correct) answer for each question and enter it on your answer sheet. Potentially useful data: -1 R = L atm mol -1 K 1 atm = 760 Torr = 760 mm Hg Avogadro s number: x Speed of light: c = 3.00 x 10 8 m/s Planck constant: h = 6.63 x J s E = hc/λ = hν 1 Hz = 1 sec -1 q = c m ΔT specific heat of water = 4.18 J g -1 C Please choose the letter a as your answer for this question. 2. Which of the following statements concerning the atom is false? a. Chemical reactions involve only the electrons. b. The atom contains protons, neutrons and electrons. c. Electrons are found in orbits about the nucleus. d. The nucleus contains only neutrons. e. Most of the mass of the atom is found in the nucleus. 3. Which sample contains the fewest atoms? a. 10 g of C b. 10 g of Ne c. 10 g of F d. 10 g of N e. 10 g of O 4. Which of the following compounds can be dissolved in water to give a solution that conducts electricity? a. CCl 4 (carbon tetrachloride) b. (CH 3 ) 2 CHOH (isopropyl alcohol) c. C 12 H 22 O 11 (sucrose) d. C 6 H 14 (hexane) e. Ba(NO 3 ) 2 (barium nitrate) 5. For the reaction given below, how many moles of AlBr 3 will be produced if 10 moles of aluminum and 12 moles of bromine are combined? 2 Al + 3 Br 2 2 AlBr 3 a. 4 b. 8 c. 12 d. 16 e. 40 Page 1 of 9

2 6. The Roman numerals in the reaction given represent the coefficients in the balanced chemical equation. What are the values of the coefficients? I Fe 3 O 4 + II H 2 III Fe + IV H 2 O I II III IV a b c d e In the reaction below, 8.0 g of H 2 react with 7.0 g of O 2. Which of the following statements is incorrect? 2 H 2 + O 2 2 H 2 O a. More moles of hydrogen are consumed than moles of oxygen. b. More grams of hydrogen are consumed than grams of oxygen. c. More grams of oxygen are consumed than grams of hydrogen. d. More moles of water are produced than moles of oxygen are consumed. e. More grams of water are produced than grams of oxygen are consumed. 8. Which reaction shows the reduction of hydrogen? a. HCl (aq) + NaOH (aq) NaCl (aq) + H 2 O (l) b. 2 Na (s) + 2 H 2 O (l) 2 NaOH (aq) + H 2 (g) c. CaO (s) + H 2 O (l) Ca(OH) 2 (s) d. 2 HClO 4 (aq) + CaCO 3 (s) Ca(ClO 4 ) 2 (aq) + H 2 O (l) + CO 2 (g) e. none of the above reactions are oxidation-reduction reactions 9. What is the oxidation number of C in CaCO 3? a. +4 b. +1 c. 0 d. -2 e Electromagnetic radiation has a frequency of Hz. What is its wavelength (in nm)? a nm b nm c nm d nm e. 550 nm 11. Which electronic transition in the hydrogen atom results in the emission of light of the shortest wavelength? a. n = 4 to n = 3 b. n = 1 to n = 2 c. n = 1 to n = 6 d. n = 5 to n = 2 e. n = 4 to n = 5 Page 2 of 9

3 12. What is the frequency (s -1 ) of a photon that has an energy of J? a. 436 b c d e Which answer shows all possible values of the second quantum number when n = 3? a. l = 0 b. l = 0, 1 c. l = 0, 1, 2 d. l = 0, 1, 2, 3 e. l = 0, 1, 2, 3, The d orbitals occur in groups of and hold up to electrons. a. 3, 6 b. 4, 8 c. 5, 10 d. 6, 12 e. 7, What is the correct ground state electron configuration for aluminum? a. 1s 2 2s 1 b. 1s 2 2s 2 2p 4 3s 2 3p 3 c. 1s 2 2s 2 2p 6 3s 2 3p 1 d. 1s 2 2s 2 2p 2 3s 2 3p 2 3d 2 4s 1 e. 1s 2 2s 2 2p 2 3s 2 3p 2 4s 2 5s Which atom or ion has the following ground state electron configuration: 1s 2 2s 2 2p 6 3s 2 3p 6? a. Kr b. Ca + c. K + d. Cl 2- e. P Which of these elements has the largest first ionization energy? a. Be b. Ca c. Mg d. Sr e. Ba Page 3 of 9

4 18. How much energy is required to raise the temperature of g of water by 25.0 C? a kj b kj c kj d. 210 kj e kj 19. The temperature of a 21.6 g sample of a metal rises from C to C when 60.0 J of energy is applied to it. What is the identity of the metal? a. silver (specific heat = J g -1 C -1 ) b. copper (specific heat = J g -1 C -1 ) c. iron (specific heat = J g -1 C -1 ) d. lead (specific heat = J g -1 C -1 ) e. aluminum (specific heat = J g -1 C -1 ) 20. What is the enthalpy change when 22.5 g of methane are burned in excess O 2? a kj b kj c kj d kj e kj CH 4 (g) + 2O 2 (g) CO 2 (g) + 2H 2 O(l) 21. A ΔH corresponds to an process. a. negative, endothermic b. positive, endothermic c. positive, exothermic d. zero, exothermic e. zero, endothermic Page 4 of 9 H = -890 kj 22. The temperature of 3.50 kg of water is raised by 1.17 C when 1.00 g of hydrazine N 2 H 4 is burned in a bomb calorimeter. The calorimeter has a heat capacity of 883 J/ C. How much heat is given off by the sample? a kj b kj c kj d kj e kj 23. Of the following, ΔH f is not zero for. a. O 2 (g) b. N 2 (l) c. C (s) d. F 2 (g) e. Al (s)

5 24. Based on the following thermochemical equation below, which statement is false? N 2 (g) + 3 H 2 (g) 2 NH 3 (g) H = kj a. For the reverse process, H = kj. b. The value of kj applies to the formation of two moles of NH 3. c. This is an endothermic reaction. d. Per mole of N 2, H = kj. e. Per mole of H 2, H = kj. 25. Determine the heat of reaction for the process C 2 H 4 (g) + 6HCl(g) 2CHCl 3 (g) + 4H 2 (g) using the information given below: 2C(s) + 2H 2 (g) C 2 H 4 (g) H 2 (g) + Cl 2 (g) 2HCl(g) C(s) + 1/2H 2 (g) + 3/2Cl 2 (g) CHCl 3 (g) a kj b kj c kj d kj e kj H = 52.3 kj H = kJ H = kj 26. The standard enthalpies of formation for several substances are given below: FeCl 3 (s) = kj/mol FeCl 2 (s) = kj/mol HCl(g) = kj/mol HCl(aq) = kj/mol H 2 O(g) = kj/mol Calculate the H for the reaction below. 2FeCl 2 (s) + 2HCl(g) 2FeCl 3 (s) + H 2 (g) a kj b kj c kj d kj e kj 27. Which statement concerning the interaction between two atoms is incorrect? a. If two atoms are widely separated, there is very little attraction between them. b. When two atoms are one bond length apart, the electrons on one atom are attracted to the nucleus of the other atom. c. When two atoms get too close together, repulsion occurs. d. A covalent bond occurs when electrons are shared between two nuclei. e. As atoms get closer together, their electrons attract each other. Page 5 of 9

6 28. How many valence electrons will be in the correctly drawn Lewis Structure for CH 3 CH 3? a. 8 b. 10 c. 14 d. 18 e Which of the following statements cannot be used to describe a covalent bond? a. The sharing of two electrons between two atoms b. The sharing of four electrons between two atoms c. An electrostatic interaction between two oppositely charged ions d. The sharing of two or more electrons equally between two atoms e. The sharing of two or more electrons unequally between two atoms 30. Write the correct Lewis dot structure for CO 2. Which statement correctly describes the structure of the whole molecule? a. There are two double bonds and four lone pairs. b. There are two double bonds and six lone pairs. c. There is a single bond, a double bond and four lone pairs. d. There are two single bonds and six lone pairs. e. There is a single bond, a double bond, and six lone pairs. 31. Which bond is expected to be shortest? a. C-O b. O-O c. N-O d. O-F e. O-S 32. Which of the following represents a nonpolar covalent bond? a. H-O b. C-N c. C-C d. Li-F e. B-Cl 33. Which of these elements is the most electronegative? a. sulfur b. iodine c. oxygen d. aluminum e. carbon Page 6 of 9

7 34. Write the singly bonded Lewis dot structure for BF 3. Which of the following statements best describes this structure? a. It obeys the octet rule on all atoms. b. It has less than an octet on at least one atom. c. It has a lone pair of electrons on the boron atom. d. It has less than an octet of electrons on all atoms. e. It exceeds the octet rule. 35. How many lone pairs of electrons does the Lewis dot structure of H 2 S have around its central atom and what is the shape of the molecule? a. 0, linear b. 0, bent (or angular) c. 1, triangular (or trigonal) planar d. 2, tetrahedral e. 2, bent (or angular) 36. In VSEPR Theory, under which of the following conditions will the electron-pair geometry always be the same as the molecular geometry? a. in molecules with at least one lone pair of electrons on the central atom b. in molecules with no lone pairs of electrons on the terminal atoms c. in molecules with a central atom that is a nonmetal d. in molecules with no lone pairs of electrons on the central atom e. in molecules where the central atom exceeds the octet rule 37. Which molecule is nonpolar? a. CH 3 Cl b. CH 2 Cl 2 c. CHCl 3 d. CCl 4 e. HCl 38. London (or dispersion) forces exist a. for all molecules. b. only for molecules with nonpolar bonds. c. only for molecules with polar bonds. d. only for molecules with ionic bonds. e. only for molecules with hydrogen bonding. 39. Which of the following interactions must be overcome when CH 3 OCH 3 boils? I. London (or dispersion) forces II. dipole-dipole attractions III. hydrogen bonding a. I only b. II only c. III only d. I and II e. I, II and III Page 7 of 9

8 40. According to kinetic-molecular theory, in which of the following gases will the average speed of the molecules be the highest at 200 C? a. HCl b. Cl 2 c. H 2 O d. SF 6 e. None. The molecules of all gases have the same average speed at any given temperature. 41. If, at constant temperature, the volume of a flask of ideal gas equipped with a moveable piston is reduced to 1/4 its original volume, what must happen to the pressure? a. It is increased by a factor of four. b. It is increased by a factor of eight. c. It is reduced to 1/4 the original pressure. d. It is reduced to 1/8 the original pressure. e. It remains the same as the original pressure. 42. What is the pressure (in atm) exerted by a 2.0 mole sample of gas that occupies 2.5 L at 34 C? a. 40 b. 20 c. 81 d e Suppose that at STP a gas occupies 10.2 L. At what temperature ( C) will the same gas occupy ml at 1550 torr? a C b C c. 545 C d C e. 0 C 44. A 1.44-g sample of an unknown pure gas occupies a volume of L at a pressure of 1.00 atm and a temperature of 100 C. The unknown gas is. a. argon b. helium c. krypton d. neon e. xenon Page 8 of 9

9 45. What volume (in L) of oxygen at 298K and 1.50 atm is required for the complete combustion of 25.0 g of hexane? 2 C 6 H O 2 12 CO H 2 O a b c d e A mixture of H 2 (g) and Cl 2 (g) exerts a total pressure of 2.50 atm. If the mole fraction of H 2 is 0.490, what is the partial pressure (in atm) of H 2? a b c d e Under what conditions do real gases most closely approximate the behavior of ideal gases? a. high pressure and high temperature b. high pressure and low temperature c. standard temperature and pressure d. low pressure and high temperature e. low pressure and low temperature 48. Of the following, is a significant greenhouse gas. a. O 2 b. H 2 O c. Cl 2 d. C 2 H 4 e. Xe Page 9 of 9

10 chem101f09_examfinala Answer Section MULTIPLE CHOICE 1. ANS: A PTS: 0 2. ANS: D PTS: 1 3. ANS: B PTS: 1 4. ANS: E PTS: 1 5. ANS: B PTS: 1 6. ANS: C PTS: 1 7. ANS: B PTS: 1 8. ANS: B PTS: 1 9. ANS: A PTS: ANS: E PTS: ANS: D PTS: ANS: B PTS: ANS: C PTS: ANS: C PTS: ANS: C PTS: ANS: C PTS: ANS: A PTS: ANS: A PTS: ANS: C PTS: ANS: C PTS: ANS: B PTS: ANS: D PTS: ANS: B PTS: ANS: C PTS: ANS: D PTS: ANS: D PTS: ANS: E PTS: ANS: C PTS: ANS: C PTS: ANS: A PTS: ANS: D PTS: ANS: C PTS: ANS: C PTS: ANS: B PTS: ANS: E PTS: ANS: D PTS: ANS: D PTS: ANS: A PTS: ANS: D PTS: ANS: C PTS: ANS: A PTS: 1 Page 10 of 9

11 42. ANS: B PTS: ANS: C PTS: ANS: E PTS: ANS: D PTS: ANS: D PTS: ANS: D PTS: ANS: B PTS: 1 Page 11 of 9