101
Examination Chemistry 2(A), June 16, 2006
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PRINT NAME______________________________ SIGNATURE_________________________ Last First Recitation Instructor_________________ There is 1 question in Part I and 18 multiple choice questions in Part II, in addition to one page of equations and a Periodic Table with constants, for a total of 10 pages. Be sure you have a complete copy before you begin. The backs of pages 3-11 can be used as scrap paper. Turn in pages 1 and 2. Part I. Answer each question in the space provided on the page. You must show your work for credit. Part II: For each question choose the one best answer. Indicate the letter corresponding to this answer in the proper space in the box to the left. It is best to use pencil and erase completely any answers you want to change. Questions with more than one answer marked will be graded as incorrect. Do not leave any answers blank - guess if you don't know. A 2 3 4 5 6 7 8 9 Part I Part II Total __________(10) __________(90) __________(100) 10 11 12 13 14 15 16 17 18 version A 19 A x x B C D E x x x x x x x x x x x x x x x B C D % E correct x 48% 63% 81% 41% 67% 67% 65% 44% 76% 61% 43% 33% 26% 46% 41% 31% 33% 56%
Chemistry 101 Part I.
Examination 2(A), June 16, 2006
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NAME______________________________
1.
(10 points) When 50.0 mL of 0.400 M Ca(OH)2(aq) is added to 50.0 mL of 0.400 M H3PO4(aq), a precipitate of Ca3(PO4)2(s) forms. The balanced equation is below. H for this reaction is -83.35 kJ/mol. The initial temperature of both solutions is 25.0 C. What is the final solution temperature, assuming the total mass is 100.0 g and the specific heat of the final solution is 4.18 J/g- C? 2 H3PO4(aq) + 3 Ca(OH)2(aq) Ca3(PO4)2(s) + 3 H2O(l) H = -83.35
kJ/mol. Ca(OH)2 is limiting reagent 1 point
(0.0500 L)(0.400 M Ca(OH)2)(1 mol reaction/3 mol Ca(OH)2) = 6.67x10-3 mol reaction 2 points (6.67x10-3 mol reaction)(-83.35 J/mol)(1000 J/kJ) = -556 J 3 points qsolution = -qreaction = +556 J = (100.0 g)(4.18 J/C-g)(T-25.0 C) 4 points T = 26.3 C 1 point
Chemistry 101
Examination 2(A), June 16, 2006
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Part II. Each question is worth 5 points. 2. Which of the following represent processes with positive values for E for the process described? (i) a burning piece of coal. (ii) compressing a ballon to a smaller volume (iii) melting an ice cube (a) only i 3. (b) only ii (c) only iii (d) i and ii (e) ii and iii
Given the following values for the heats of formation, what is the number of moles of ethane (C2H6) required to produce 1.00x103 kJ of heat by combustion to CO2 (g) and H2O (l). C2H6 (g) + 7/2 O2(g) C2H6 (g) CO2 (g) H2O (l) (a) 1.56 (d) 1.68 2 CO2 (g) + 3 H2O (l)
Hf = -84.7 kJ/mol Hf = -393.5 kJ/mol Hf = -285.8 kJ/mol (b) 0.641 (c) can't be determined without Hf for O2
(e) 0.595
4.
Using Hess's Law and some or all of equations (1) - (3) below calculate H at 25 C for the combustion of C2H5OH(l): C2H5OH(l) + 3O2(g) 3H2O(l) + 2CO2(g) C2H5OH(l) H = ? H = -278 kJ/mol H = -1411 kJ/mol H = -44 kJ/mol (c) +632 kJ/mol
1. 2 C(graphite) + 3H2(g) + 1/2 O2(g) 2. C2H4(g) + 3O2(g) 3. C2H4(g) + H2O(l) (a) -1742 kJ/mol (d) -1367 kJ/mol
2CO2(g) + 2H2O(l) C2H5OH(l) (b) +44 kJ/mol (e) -1733 kJ/mol
Chemistry 101 5.
Examination 2(A), June 16, 2006
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Which statement correctly describes the general periodic trends in ionization energy and electron affinity? (a) Both decrease from left to right across a row and both decrease down a group. The lowest ionization energy in a row is for Group 7A. The lowest electron affinity in a row is for Group 7A. (b) Both increase from left to right across a row and both increase down a group. The highest ionization energy in a row is for Group 7A. The highest electron affinity in a row is for Group 7A (c) Ionization energy increases from left to right across a row and decreases down a group. Electron affinity decreases across a row and increases down a group. The highest ionization energy in a row is for Group 8A. The highest electron affinity in a row is for Group 1A. (d) Both increase from left to right across a row and both decrease down a group. The highest ionization energy in a row is for Group 8A. The highest electron affinity in a row is for Group 7A (e) Both decrease from left to right across row a and both increase down a group. The highest ionization energy in a row is for Group 1A. The highest electron affinity in a row is for Group 2A
6. What is the frequency of light in units of s-1 (absorbed or emitted) for a hydrogen atom involved in a transition from an electron in a n = 5 orbital to a n = 2 orbital? 1/ = R H(1/m2 1/n2) where RH = 1.1x107 m-1. (a) 6.9x1014, emitted (b) 6.9x1014, absorbed (c) 2.3x106, emitted (d) 2.3x106, absorbed (e) 4.3x107, emitted 7. The electron configuration of Fe and the number of unpaired electrons are (a) [Ar] 4s2 3d6, 6 unpaired electrons (b) [Ar] 4s2 4p6, 0 unpaired electrons (c) [Ar] 3d8, 2 unpaired electrons (d) [Ar] 4s2 3d6, 4 unpaired electrons (e) [Ar] 4s2 3d6, 0 unpaired electrons
Chemistry 101 8.
Examination 2(A), June 16, 2006
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The electron configuration of the 49In1+ ion is (a) [Kr]4d105s25p1 (d) [Kr]4d105s15p1 (b) [Kr]4d105s2 (e) [Kr]4d95s25p1 (c) [Kr]5s2
9.
If 30.0 mL of water at 7 C is mixed with 50.0 mL of water at 57 C, what is the final temperature of the mixture? The specific heat of water is 4.186 J/C-g. Hint: The heat lost by the hot water is gained by the cold water. (a) 17 (b) 38 (c) 32 (d) 47 (e) 53
10.
Which of the following is an allowed set of four quantum numbers? (a) n = 5, l = 4, ml = -4, ms = -1/2 (b) n = 2, l = 2, ml = 1, ms = +1/2 (c) n = 7, l = 2, ml = 0, ms = +1 (d) n = 2, l = 1, ml = 2, ms = +1/2 (e) n = 7, l = -2, ml = 1, ms = +1/2 (e) n = 7, l = -2, ml = 1, ms = +1/2
11.
Which equations give the correct products for the indicated reactants? (1) 2 Na(s) + 2 H2O(l) H2(g) + 2 NaOH (aq) (2) 4 Na(s) + 2 H2O(l) Na2O(aq) + 2 NaH (aq) (3) BaO(s) + H2O(l) Ba(OH)2(aq) (4) 2 BaO(s) + 2 H2(g) O2(g) + 2 BaH2(s) (a) 1 and 3 (e)1 only (b) 2 and 3 (c) 1 and 4 (d) 2 and 4
Chemistry 101 12.
Examination 2(A), June 16, 2006
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Which of the following statements correctly describe the properties of elements in Groups 1A, 2A, and 7A? 1. In Group 1A reactivity increases from Li to Cs.
2. Group 2A is more reactive than the elements in the same period in Group 1A, and reactivity decreases from Be to Ba. 3. In Group 7A reactivity decreases from F2 to I2. 4. Group 2A is more reactive than the elements in the same period in Group 1A, and reactivity increases from Be to Ba. (a) 1 only 13. (b) 3 and 4 (c) 1 and 4 (d) 1 and 3 (e) 1 and 2
The first five ionization energies (kJ/mol) for an unknown element are: I1 578 The element is (a) Si (b) Na (c) Mg (d) Al (e) P I2 1817 I3 2745 I4 11,575 I5 14,830
14.
The Auf Bau Principle, Hund's rule, and the Pauli exclusion principle are used to determine the lowest energy electron configuration of an atom, called the ground state; any other possible configuration is higher in energy, an excited state. Which of the following electron configurations are excited states? 2s 2px 2py 2pz
(1) (2) (3) (4) (a) 3 only (b) 4 only (c) 3 and 4 (d) 2 and 3 (e) 1 only
Chemistry 101 15. (a) 128 16.
Examination 2(A), June 16, 2006
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How many orbitals exist having the principal quantum number 8? (b) 64 (c) 32 (d) 25 (e) 8
How many electrons could occupy the 5g sub-shell? (a) none (b) 50 (c) 16 (d) 18 (e) 20
17.
Which of the following reactions would have the enthaply of formation of CH 3OH(l) at 298 K? (a) C(g) + 2 H2(g) + 1/2 O2(g) CH3OH(l) CH3OH(l)
(b) C(graphite) + 2 H2(g) + 1/2 O2(g) (c) C(g) + 4 H(g) + O(g) (d) CO(g) + 2 H2(g) CH3OH(l) CH3OH(l)
(e) C(diamond) + 2 H2(g) + 1/2 O2(g)
CH3OH(l)
18.
Which of the following is the order of increasing ionization energy in the gas phase? 1. Mg Mg+ + e 2. Si Si+ + e 3. Ar Ar+ + e 4. K+ K2+ + e (a) 1 < 2 < 3 < 4 (d) 3 < 4 < 2 < 1 (first ionization energy of Mg) (first ionization energy of Si) (first ionization energy of Ar) (second ionization energy of K) (b) 4 < 1 < 2 < 3 (e) 3 < 2 < 1 < 4 (c) 4 < 3 < 2 < 1
Chemistry 101
Examination 2(A), June 16, 2006
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19. For a poly-electron atom, which line below properly describes the quantum numbers associated with each property shape of the average distance energy of the orientation of the orbital from the nucleus orbital orbital in space (a) ml n n only l (b) l n l and n ml (c) l l and n l and n ml (d) l n n only ml (e) l n l only ml