Attempt all the questions and circle/write your answers. For Section 2 attempt all questions and show all your steps clearly

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1 Chemistry 111 EXAM 2_Summer 2012 NAME: SECTION #: Attempt all the questions and circle/write your answers. For Section 2 attempt all questions and show all your steps clearly Constants and formulas: E=h, c=, h = x J.s, c = 3.00 x 10 8 m/s, 1nm = 10-9 m 1. What products result from the addition of aqueous solutions of Fe(C 2 H 3 O 2 ) 2 (aq) and Na 3 PO 4 (aq)? a) FePO 4 (s) and Na 3 (C 2 H 3 O 2 ) 2 (aq) b) Fe 3 (PO 4 ) 2 (s) and NaC 2 H 3 O 2 (aq) c) Fe 3 (PO 4 ) 2 (s) and NaC 2 H 3 O 2 (s) d) FePO 4 (s) and Na 3 (C 2 H 3 O 2 ) 2 (s) e) FeP(s), CO 2 (g), H 2 O(l), NaOH(aq), and PH 3 (g). 2. Which net ionic equation best represents the reaction that occurs when an aqueous solution of barium iodide is mixed with an aqueous solution of sulfuric acid? a) BaI 2 + H 2 SO 4 BaSO 4 + 2HI b) 2H + (aq) + 2I (aq) 2HI(g) c) Ba 2+ (aq) + SO 2 4 (aq) BaSO 4 (s) d) Ba 2+ (aq) + 2I (aq) + 2H + (aq) + SO 2 4 (aq) BaSO 4 (s) + 2HI(g) e) No net reaction occurs. 3. In order to dilute 45.9 ml of M HCl to M, the volume of water that must be added is a) ml. b) 40.0 ml. c) 5.86 ml. d) ml. e) ml. 4. The reaction of HCl with NaOH is represented by the equation HCl(aq) + NaOH(aq) NaCl(aq) + H 2 O(l) What volume of M HCl is required to titrate 45.1 ml of M NaOH? a) 45.1 ml b) 26.8 ml c) 4.82 ml d) 75.9 ml e) 3.97 ml ~ 1 ~

2 5. What volume of 0.10 M sodium bromide, NaBr, contains mol of bromide ions? a) 0.30 L b) L c) ml d) 3.3 ml e) 1.7 ml 6. H 2 and F 2 react according to the following equation, forming HF. H 2 (g) + F 2 (g) 2HF(g); H = 271 kj If H 2 (g) and F 2 (g) were mixed in a thermally insulated vessel, the reaction that occurred would be a) exothermic, and the temperature of the reaction system would rise. b) endothermic, and the temperature of the reaction system would rise. c) endothermic, and the temperature of the reaction system would fall. d) exothermic, and the temperature of the reaction system would fall. e) We could not tell unless the original and final temperatures were given. 7. Given: 4AlCl 3 (s) + 3O 2 (g) 2Al 2 O 3 (s) + 6Cl 2 (g); H = kj determine H for the following thermochemical equation. Cl 2 (g) + ⅓Al 2 O 3 (s) ⅔AlCl 3 (s) + ½O 2 (g) a) kj b) kj c) kj d) kj e) kj 8. Which of the following statements is false concerning the reaction of hydrogen gas and oxygen gas given below? H 2 (g) + ½O 2 (g) H 2 O(l); H = kj a) If the equation is multiplied by 2, H becomes kj. b) If the equation is reversed, H becomes kj. c) Per mole of O 2, the change in enthalpy is kj. d) The value kj pertains to 1 mol of liquid water. e) For the reaction H 2 (g) + ½O 2 (g) H 2 O(g), H is not equal to kj. 9. What is the quantity of heat evolved at constant pressure when 60.9 g H 2 O(l) is formed from the combustion of H 2 (g) and O 2 (g)? H 2 (g) + ½O 2 (g) H 2 O(l); H = kj a) kj b) kj c) kj d) kj e) 84.5 kj ~ 2 ~

3 10. The quantity of heat required to raise the temperature of a sample of a substance by 1 C is the sample s a) heat capacity. b) specific heat. c) enthalpy. d) work. e) calorimetry. 11. Consider the following metals. Metal Specific Heat copper magnesium mercury silver lead J/(g C) 1.02 J/(g C) J/(g C) J/(g C) J/(g C) If the same amount of heat is added to 25.0 g of each of the metals, which are all at the same initial temperature, which metal will have the highest final temperature? a) copper b) magnesium c) mercury d) silver e) lead 12. Given: Fe 2 O 3 (s) + 3CO(g) 2Fe(s) + 3CO 2 (g); H = 26.8 kj FeO(s) + CO(g) Fe(s) + CO 2 (g); H = 16.5 kj determine H for the following thermochemical equation. Fe 2 O 3 (s) + CO(g) 2FeO(s) + CO 2 (g) a) 43.3 kj b) 10.3 kj c) 6.2 kj d) 10.3 kj e) 22.7 kj 13. All of the following have a standard enthalpy of formation value of zero at 25 C except a) CO(g). b) Fe(s). c) C(s). d) F 2 (g). e) Ne(g). ~ 3 ~

4 14. Which of the following statements is incorrect? a) The product of wavelength and frequency of electromagnetic radiation is a constant. b) As the energy of a photon increases, its frequency decreases. c) As the wavelength of a photon increases, its frequency decreases. d) As the frequency of a photon increases, its wavelength decreases. e) As the wavelength of a photon increases, its energy decreases. 15. A photon of red light has a frequency and a wavelength than a photon of blue light. a) lower, longer b) higher, longer c) lower, lower d) higher, shorter e) lower, shorter 16. What is the wavelength of a photon having a frequency of 87.9 THz? (1 THz = Hz, c = m/s, h = J s) a) nm b) nm c) nm d) 3.41 nm e) nm 17. From the Bohr model of the hydrogen atom, we can conclude that the energy required to excite an electron from n = 6 to n = 7 is the energy required to excite an electron from n = 7 to n = 8. a) less than b) greater than c) equal to d) either equal to or less than e) either equal to or greater than 18. What is the wavelength of light emitted when the electron in a hydrogen atom undergoes a transition from level n = 9 to level n = 4? (c = m/s, h = J s), R H = J) a) m b) m c) m d) m e) m 19. The square of the wave function, ψ 2, of an electron in an atom a) describes the energy of the electron. b) specifies the momentum of the electron. c) gives the probability of finding the electron in a region of space. d) is proportional to the velocity of the electron. e) is inversely proportional to the distance between the electron and the nucleus. ~ 4 ~

5 20. Which of the following combinations of quantum numbers is permissible? a) n = 3, l = 3, m l = 1, m s = ½ b) n = 4, l = 3, m l = 4, m s = ½ c) n = 3, l = 2, m l = 1, m s = +½ d) n = 1, l = 2, m l = 0, m s = ½ e) n = 2, l = 1, m l = 1, m s = How many total orbitals are in the n = 5 shell? a) 36 b) 1 c) 3 d) 5 e) The angular momentum quantum number (l) is best associated with the a) energy of the orbit. b) energy of the orbital. c) number of orbitals in a subshell. d) orientation in space of an orbital. e) shape of the orbital. 23. An orbital with the quantum numbers n = 5, l = 2, m l = 2 may be found in which subshell? a) 5s b) 5p c) 5d d) 5f e) 5g 24. What is the wavelength of a 148-g baseball traveling at 94.5 mph? (1 mi = km, 34 h J s, 1h =3600 s) a) m b) m c) m d) m e) m 25. What is the balanced oxidation half-reaction for the following reaction? Cu 2+ (aq) + Fe(s) Cu(s) + Fe 2+ (aq) a) Cu 2+ (aq) + 2e Cu(s) b) Fe 2+ (aq) + 2e Fe(s) c) Fe(s) Fe 2+ (aq) + 2e d) Cu(s) + 2e Cu(s) e) Cu(s) Cu 2+ (aq) + 2e ~ 5 ~

6 Section 2 (25 points) 26. The concentration of Pb 2+ in a sample of wastewater is to be determined by using gravimetric analysis. To a mL sample of the wastewater is added an excess of sodium sulfide, forming the insoluble lead (II) sulfide ( g/mol) according to the balanced equation given below. The solid lead (II) sulfide is dried, and its mass is measured to be g. What was the concentration of Pb 2+ in the original wastewater sample? Pb 2+ (aq) + Na 2 S(aq) PbS(s) + 2Na + (aq) What is the mass in grams of lead in this water sample? ~ 6 ~

7 27. What is the standard enthalpy of formation of liquid diethylamine, (CH 3 CH 2 ) 2 NH? N 2 O 5 (g) + 8CH 4 (g) 2(CH 3 CH 2 ) 2 NH(l) + 5H 2 O(l); H = 1103 kj Substance H f (kj/mol) N 2 O 5 (g) CH 4 (g) 74.9 H 2 O(l) ~ 7 ~

8 28. What is the energy per mole of photons with a wavelength of nm? (c = m/s, h = J s, N A = mol -1 ) END ~ 8 ~