Chemistry 16
nd
Sample 2 Long Exam
General Instructions Read all directions carefully and as much as possible correctly answer the questions that follow. Use of non-programmable calculators is allowed. No other computational devices can be used. Cheating is strictly prohibited. Good luck!
I.
MULTIPLE CHOICE. Choose the best answer among the five choices provided. Write the letter of the correct answer on the left side of o f the question number. [2 points each]
1. Which of the following statement/s correctly describes a calorie? o I. It is the amount of energy required to lower the temperature of 1 mg of water from 15.5 C to o 14.5 C. o II. It is the amount of energy required to raise the temperature of 1 mg of water from 14.5 C to o 15.5 C. III. It is an SI unit describing the energy changes accompanying chemical reactions. IV. It is an SI unit describing how much heat is released from a chemical reaction. A. I and III B. I and IV C. II and III D. II and IV E. None 2. Suppose that a cylinder contains both nitrogen and oxygen gases and that the cylinder is topped with a movable piston. If a reaction occurs between the gases, 1250 J of heat is lost from the system and into the surroundings. This, however, also causes the gases t o expand due to heating up. 500 J of work is done by the gases on the surroundings. Calculate the change in internal e nergy of the system. A. +1750 J B. -1750 J C. +750 J D. -750 J E. 0 J 3. Which of the following statements is TRUE? A. A positive ΔH value means that the system has gained heat from the surroundings, which is an exothermic process. B. A positive ΔH value means that the system has lost heat to its surroundings, which is an endothermic endothermic process. C. A negative ΔH value means that the system has gained heat from the surroundings, which is an exothermic process. D. A negative ΔH value means that the system has lost heat to its surroundings, which is an endothermic process. E. None of the above 4. Which of the following statements is FALSE? A. Enthalpy is a quantity-dependent property. B. If the vaporization of water is an endothermic reaction, then its condensation is an exothermic reac tion. C. The vaporization of water releases more heat than the condensation of water. D. Hess’s Law states that if a reaction is carried out in a stepwise fashion, the enthalpy change for the reaction will just equal the sum of the enthalpy changes for the individual steps. E. The enthalpy change for the vaporization of water is different from the enthalpy change for the sublimation of ice. 5. How much energy (in J) can one obtain from a biscuit containing 12.5 Calories? 4 4 3 A. 52.3 J B. 5.23 x 10 J C. 5.18 x 10 J D. 51.8 J E. 2.99 x 10 J 6. The combustion of liquid methanol, CH3OH, releases 726.5 kJ of heat: CH3OH(l) + 3/2O2(g) CO2(g) + 2H2O(l), ΔH = -726.5 kJ How much heat is released when 6.40 g of liquid methanol is combusted under constant pressure? 1
A. -145 kJ
B. -72.7 kJ
C. -130 kJ
D. -131 kJ o
E. -105 kJ
o
7. How much heat is needed to warm 300 g of water from 15 C to 50 C? The specific heat of water is 4.18 4 J/gK. 3 4 4 A. 44 J B. 1.3 x 10 J C. 72 J D. 4.4 x 10 J E. 7.2 x 10 J 8. Which of the following statements is TRUE? A. The heat capacity of an object is the amount of heat required to raise its temperature by 10 K. B. The heat capacity of 1 mol of substance is called its specific heat. o C. The heat capacity of an object is the amount of heat required to lower its temperature by 1 C. D. The greater the heat capacity, the greater the heat required to produce a rise in temperature. E. C and D 9. What is the standard enthalpy change for the combustion of 1.00 mol of propane, C 3H8? Use the following: o o o ΔH f (CO2) = -393.5 kJ, ΔH f (H2O) = -285.8 kJ, ΔH f (C3H8) = -103.85. A. -2220 kJ/mol B. -50.3 kJ/mol C. -1450 kJ/mol D. -2445 kJ/mol E. -2002 kJ/mol 10. When 1.00 g of ammonium nitrate, NH4NO3, dissolves in 50.0 g of water in a calorimeter, the temperature of o o water drops from 25.0 C to 23.32 C. Assuming that all of the heat absorbed by the reaction comes from the water, calculate the heat of reaction. A. -204 J B. -351 J C. +295 J D. +345 J E. -308 J For numbers 11 to 12, refer to the following: One mole of Ni(CO) 4 gas decomposes upon heating to Ni solid and CO. In addition, 100.7 k J of heat is absorbed.
11. Calculate the ΔH when 1.00 g of Ni(CO)4 decomposes. A. 0.590 kJ B. 0.450 kJ C. 0.540 kJ
D. 0.570 kJ
E. 0.495 kJ
12. How many grams of Ni(CO)4 decomposes when the heat absorbed is 10.0 kJ? A. 21.0 g B. 15.0 g C. 11.0 g D. 17.0 g
E. 19.0 g
13. In which of the following reactions is/are ΔS positive? I. H2O(l) H2O(g) + II. Ag (aq) + Cl (aq) AgCl(s) III. 4Fe(s) + 3O2(g) 2Fe2O3(s) A. I only B. II only C. III only
E. I and III
D. I and II
14. When ΔH is ______________, and ΔS is _______________, the reaction is non -spontaneous at all conditions. A. positive… negative D. negative… negative B. negative… positive E. zero… positive C. positive… positive 15. When ΔH is ______________, and ΔS is _______________, the reaction is spontaneous at low temperatures. A. positive… negative D. negative… negative B. negative… positive E. zero… positive C. positive… positive 16. Which of the following is an impossible set of quantum numbers for an ele ctron? A. n = 2, l = 1, ml = 1 C. n = 4, l = 2, ml = -2 B. n = 1, l = 0, ml = -1 D. n = 5, l = 4, ms = -1/2
2
E. n = 3, l = 2, ml = 0 17. What is the maximum number of electro ns that can occupy the 3d subshell? A. 2 B. 5 C. 7 D. 9
E. 10
18. What is the maximum number of electro ns that can be present in the electron shell with n = 2? A. 2 B. 4 C. 8 D. 16 E. 32 19. What is the maximum number of electrons in an atom that can have the following quantum numbers: n = 5, l = 3, ms = +1/2? A. 7 B. 25 C. 24 D. 6 E. 14 20. Which of the following states that the lowest energy level-orbital must be filled first by electro ns? A. Pauli Exclusion Principle D. Periodic Law B. Aufbau Principle E. Octet Rule C. Hund’s Rule of Multiplicity 21. How many valence electrons does cobalt have? A. 6 B. 7 C. 8
D. 9 2
E. 10
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22. What family of elements is characterized by having an ns np outer-electron configuration? Note that n is an integer from 2 to 6. A. IIIA B. IVA C. VA D. VIA E. VIIB 23. Which of the following statement/s is/are TRUE regarding the differences between the 1s and 2s orbitals? I. They are both spherical orbitals. II. The 1s orbital has lower energy than the 2s orbital. III. The average distance of the 1s electrons from the nucleus is greater than that of the 2s electrons. IV. The 2s orbital has one radial node; the 1s orbital has none. A. I, II, III, and IV B. I and II C. II, III, and IV D. I, II, and IV E. II and IV 24. Which of the following will most readily give up an electro n? A. In B. Sn C. Ga
D. Ge 2-
-
3+
E. Al 3+
25. Arrange the following in terms of increasing atomic radius: Se , Br , Ga , Al . 23+ 3+ 3+ 3+ 2A. Se , Br , Ga , Al D. Ga , Al , Br , Se 3+ 3+ 223+ 3+ B. Ga , Al , Se , Br E. Br , Se , Al , Ga 3+ 3+ 2C. Al , Ga , Br , Se 26. Which metalloid has the highest metallic character, among the choices below? A. B B. Al C. Sb D. Te
E. Po
27. Arrange the following in order of decreasing first ionization energy: Iridium, Rhodium, Palladium, Tungsten. A. Tungsten, Iridium, Rhodium, Palladium B. Iridium, Tungsten, Palladium, Rhodium C. Tungsten, Rhodium, Iridium, Palladium D. Palladium, Rhodium, Iridium, Tungsten E. Rhodium, Palladium, Tungsten, Iridium 28. Which has the most ionic bond? A. Al—Cl B. K—Br
C. Ca—Br
D. Zn—Cl
E. Mg—Cl
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29. What kind of bond is in Cu—Cl? (Electronegativity values: Cu = 1.9, Cl = 3.0) A. Ionic D. Metallic B. Polar covalent E. None of the above C. Nonpolar covalent For numbers 30 to 31, consider the following chemical structure of a hypothetical compound:
30. Which of the following has the shortest bond length? A. A—B B. B—C C. D—E
D. F—G
E. E—F
31. If A = B = C = D = E = F = G = Carbon atom, and each atom is bonded to a sufficient number of Hydrogen atoms to favor the Octet Rule, then what are the formal charges of B and F? A. +1, 0 B. 0, +1 C. -1, +1 D. 0, 0 E. -1, -1 32. What can be said about the following orbital diagram? A. The atom with the above orbital diagram is in the excited state. B. The diagram does not follow Hund’s Rule of Multiplicity. C. The diagram does not follow the Pauli Exclusion Principle. D. The orbital diagram above belongs to cobalt, in the g round state. E. The orbital diagram above belongs to iron, in the gr ound state. -
33. What is the molecular geometry of SnCl3 based on the VSEPR model? A. Linear D. Tetrahedral B. Trigonal planar E. Bent C. Trigonal pyramidal 34. Based on the Lewis structure of phosgene, Cl2CO, what would best describe the Cl—C—Cl bond angle? o o A. Equal to 120 D. Less than 109.5 o o B. Less than 120 E. Greater than 109.5 o C. Greater than 120 For numbers 35 to 38, refer to the following:
Consider the Lewis structure for glycine, the simplest amino acid:
Let C1 be the left C and C2 be the right C. 35. What is the hybridization of the orbitals on C 2? 2 3 A. sp B. sp C. sp
3
D. sp d
36. What are the hybridizations of the orbitals on t he doubly-bonded oxygen? 2 3 3 A. sp B. sp C. sp D. sp d
3 2
E. sp d
3 2
E. sp d
4
37. What is the total number of σ bonds in glycine? A. 0 B. 1 C. 5
D. 7
E. 9
38. What is the total number of π bonds in glycine? A. 0 B. 1 C. 5
D. 7
E. 9
2-
39. Predict the magnetic property and bond or der of the peroxide ion, O2 . A. Diamagnetic, 1 D. Paramagnetic, 1 B. Diamagnetic, 2.5 E. Paramagnetic, 2 C. Diamagnetic, 2 40. Which of the following would you expect to be diamagnetic? I. N222II. O2 A. II and III B. I and II C. II and IV
II.
III. Be22+ IV. C2 D. I and IV
E. I, II, and IV
PROBLEM SOLVING. Solve the following problems completely. Show your solutions.
1. When a 9.55-g sample of solid sodium hydroxide dissolves in 100.0 g of water in a coffee-cup o o calorimeter, the temperature rises from 23.6 C to 47.4 C. Calculate ΔH (in kJ/mol NaOH) for the solution process: + NaOH(s) Na (aq) + OH (aq) Assume that the specific heat of the solution is the same as that of pure water. [3 points] 2. From the enthalpies of reaction H2(g) + F2(g) 2HF(g), ΔH = -537 kJ C(s) + 2F2(g) CF4(g), ΔH = -680 kJ 2C(s) + 2H2(g) C2H4(g), ΔH = +52.3 kJ Calculate ΔH for the reaction of ethylene with F2: [5 points] C2H4(g) + 6F2(g) 2CF4(g) + 4HF(g) 3. Draw the Lewis structures of the following compounds. Write all resonance structures, if any. 2a. SO3 [2 points] b. AsF6 [2 points] c. Nitric acid [2 points] d. ICl2 [2 points] +
4. Consider the N2 ion. a. Sketch the molecular orbitals of the ion. [3 points] b. What is the bond order in N 2+? [1 point] c. Write the electron configuration of the ion in terms of its MOs. [2 points] END OF EXAM Total Number of Points = 102 points
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ANSWER KEY: 1. E 2. B 3. E 4. C 5. B 6. A 7. D 8. D 9. A 10. B 11. A 12. D 13. A 14. A 15. D 16. B 17. E 18. C 19. A 20. B 21. D 22. C 23. E 24. C 25. C 26. D 27. D 28. B 29. B 30. D 31. D 32. E 33. C 34. B 35. B 36. B
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37. 38. 39. 40.
E B A A
PROBLEM SOLVING 1. -45.7 kJ/mol 3 2. -2.49 x 10 kJ 3. :D 4. :D
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