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Unformatted text preview: Name (PRINT): ________________________________ Chem 102A Examination 3 Fall, 2008 I pledge on my honor that I have neither given nor received improper aid on this examination. ______________________________
1. No books or notes may be using during this test. There should be no data stored on your calculator for use on the exam. This includes but is not limited to periodic tables and chemical equations
2. There are a total of 9 sections (some with several parts) for a sum of 100 points.
3. Be certain that, wherever applicable, you show your work. Problems in Sections 4, 6 and 9 that
are answered without showing detailed work will not receive credit.
4. Please note: there are no intentionally misleading questions on this test. Each problem should be
taken at its face value. You must, however, be certain to read each problem carefully!
5. If you have any questions please ask your professor. DO NOT REMOVE THIS PAGE FROM YOUR EXAM!!!!! Please be sure that you are officially enrolled in the section named below: Section 2– Hanusa Exam Score________ 2
SECTION 1 (12 PTS. TOTAL; 2 PTS. EACH)
Circle either True or False for each answer.
(1) According to the VSEPR theory, BCl3 and AlCl3 molecules are
expected to have the same molecular geometry. True False (2) Of the species NO2, NO and N2, only N2 obeys to the octet rule. True False (3) Atomic radii decrease across a row from left to right in the peri- True
odic table because the effective nuclear charge decreases. False (4) Compound MgSO4 contains both ionic and nonpolar covalent
bonds. True False (5) In their gas phase, it requires less energy to remove a single
electron from oxygen atom than from nitrogen atom. True False (6) Molecules containing a central atom with sp3 hybridization will
all have tetrahedral molecular geometry. True False SECTION 2 (27 PTS. TOTAL; 3 PTS. EACH)
Pick the one best answer; if you circle more than one, you will receive NO credit!
(1) Which of the following species is paramagnetic?
e) None of these
(2) Which of the following pairs is isoelectronic?
a) Mn2+ and Ar
b) Zn2+ and Cu2+
c) Na+ and K+
d) Rb+ and Br−
e) None of these
(3) Arrange the following ions in order of increasing ionic radius: K+, P3− , S2− , Cl− .
a) K+ < Cl− < S2− < P3−
b) K+ < P3− < S2− < Cl−
c) Cl− < S2− < P3− < K+
d) Cl− < S2− < K+ < P3−
e) None of these 3
(4) Which of the following molecules has an atom with an expanded octet?
e) None of these
(5) Which of the following ionic solids would have the largest magnitude of lattice energy?
e) None of these
(6) The correct Lewis dot structure of AsCl3 will show
a) three single bonds and one lone pair of electrons on the central atom
b) two single bonds, one double bond, and 9 lone pairs of electrons on the outer
c) one single bond, two double bonds, and 8 lone pairs of electrons on the outer
d) three single bonds and two lone pair of electrons on the central atom
e) None of these
(7) Which of the following should have a dipole moment?
d) All of these
e) None of these
(8) Which of the following Lewis structures can be drawn as two or more resonance
a) CO 3 (C is the central atom)
e) NO2 (N is the central atom)
O3 (one O is the central atom)
All of these
None of these (9) Using Lewis dot structures and formal charges, which of the following ions is expected to be most stable?
a) OCN− (carbon is the central atom)
b) ONC− (nitrogen is the central atom)
c) NOC− (oxygen is the central atom)
d) None of these ions are stable
e) All of these ions are equally stable 4
SECTION 3 (10 PTS. TOTAL; 2 PTS. EACH)
In the center column, write “>”, “<”, “=”, or “?” (can’t tell) to describe the relationship
between the following quantities. The first one has been done for you. Number of Chem 102a instructors
(1) The maximum number of electrons
that an s orbital can hold. < Number of Chem 102a students
The maximum number of electrons
that a hybrid sp3 orbital can hold. (2) The angle between two equatorial
bonds in a trigonal bipyramidal
molecule. The smallest angle between two adjacent bonds in an octahedral molecule. (3) The number of lone pairs on the central atom in BrF4+. (Br is the central
atom) The number of lone pairs on the central atom in I3−. (one I is the central
atom) (4) The formal charge on the sulfur
atom in the Lewis structure of SCN− .
(carbon is the central atom) The formal charge on the sulfur atom
in the Lewis structure of SOCl2. (sulfur is the central atom, S and O are
connected via double bond) (5) The length of the nitrogen-nitrogen
bond in N2H2. The length of the nitrogen-nitrogen
bond in N2H4. SECTION 4 (6 PTS) Credit will not be given if detailed step-by-step work is not shown.
Given the following ionization energy (IE) and electron affinity (EA) values, calculate
the energy change ( E) for the reaction: Mg2+(g) + 2Cl−(g) → Mg(g) + 2Cl(g)
Atom IE1 (kJ/mol) IE2 (kJ/mol) EA (kJ/mol) Mg 738 1450 +3 Cl 1251 2300 −349 5 SECTION 5 (10 PTS. TOTAL; 2 PTS. EACH)
Match the following with the best possible answer.
(1) A binary compound formed between calcium and nitrogen would be expected to
have the formula: _____
(2) The type of hybrid orbitals used by the central atom in XeF4 is _____.
(3) The H-N-H bond angle in NH2− is closest to _____.
(4) In a molecule, the ability of an atom to attract electrons to itself is called _____.
(5) The molecular geometry of a molecule with 3 outer atoms and 2 lone pairs of electrons on the central atom is expected to be _____. (A) bent (M) CaN (Y) electronegativity (B) linear (N) Ca3N2 (Z) 90 ° (C) octahedral (O) Ca2N3 (AA) 109.5° (D) seesaw (P) sp (BB) 120° (E) square planar (Q) sp2 (CC) 180° (F) square pyramidal (R) sp3 (DD) oxygen (G) tetrahedral (S) sp3d (EE) silicon (H) T-shaped (T) sp3d2 (FF) chlorine (I) trigonal bipyramidal (U) bond energy (GG) gold (J) trigonal planar (V) ionization energy (HH) cadmium (K) trigonal pyramidal (W) lattice energy (II) arsenic (L) CaN2 (X) electron affinity (JJ) iron 6
SECTION 6 (12 PTS. TOTAL)
Complete the following table.
Chemical formula Lewis dot structure
(2 pts each) Number of electron groups
around the central atom
(1 pt each) Electron group geometry
(1 pt each) Molecular geometry
(1 pt each) Does this molecule/ion
have a dipole moment?
(1 pt each) SeCl4 IF4− 7
SECTION 7 (6 PTS. TOTAL) Credit will not be given if detailed step-by-step work is not shown.
The standard enthalpy of dissociation of H2O(g) into elemental hydrogen and oxygen
gases is +241.8 kJ/mol. The bond enthalpies in H2(g) and O2(g) molecules are 436
kJ/mol and 489 kJ/mol, respectfully. Determine the average O-H bond enthalpy (in
units of kJ/mol). SECTION 8 (7 PTS. TOTAL)
Consider the molecule shown below for the following questions. CH3
H H C
H2 C N
CH2 H m olec ular geometry? (1) In each box, indicate the hybridization (sp, sp2, sp3, sp3d, or sp3d2) about each indicated carbon atom.
(2) How many pi (π) bonds are present in this molecule? __________
(3) The molecular geometry about the indicated carbon atom is: ________________ 8
SECTION 9 (10 PTS.) Credit will not be given if detailed step-by-step work is not shown.
Construct the Born-Haber cycle to determine the second ionization energy of calcium
given the following data: Heat of sublimation of Ca(s) is 193 kJ/mol; The first ionization
energy of Ca(g) is 590 kJ/mol; The bond enthalpy in O2(g) molecule is 498 kJ/mol;
electron affinity of O(g) is -141 kJ/mol. Electron affinity of O−(g) is 878 kJ/mol. Hf of
CaO(s) is-636 kJ/mol. Lattice energy of CaO(s) is -3414 kJ/mol. 9 1 1 H H 1.00794
3 4 Li Be 6.941
11 9.01218 Na 5 Mg 22.98977
19 Ca K 39.0983
37 40.078 85.4678 87.62 55 Sc Ti 23 V 24 Cr 44.95591
41 51.9961 88.90585
57 95.94 56 132.90545 137.327 138.9055 87 88 38 Rb
Fr (223) Sr Ba
Ra (226) Y La
(227) Zr 42 91.224 Nb 92.90638 Mo 72 73 74 Hf Ta W 25 Mn A ctinide s Fe 27 Co 28 Ni 29 Cu 55.845
77 106.42 107.8682
79 Tc Re Ru
Ir 178.49 180.9479 183.84 186.207 190.23 192.217 104 105 106 107 108 Pd
78 Pt 12.0107 14.0067 15.9994 18.99840 14 15 16 17 Ag
Au (261) Db
(262) Sg (263) Bh
(262) 59 60 61 Ce Pr Nd Pm
(145) 140.116 140.90765
91 Th Pa 232.0381 231.0359 144.24
92 U 238.0289 93 Np
(237) Hs Zn 65.39
48 Cd 112.411
80 Hg 63 200.59 31 Ga 69.723
49 In 114.818
81 Tl 204.3833 P 32 33 28.0855 30.97376 Ge S 32.066 35.4527 34 35 72.61 As 74.92160 Se 50 51 52 Sn 118.710
82 Pb 207.2 Sb 78.96 Te 121.760 127.60 83 84 Bi 208.9804 Cl Po (209) Br (265) 64 94 95 157.25
96 At Rn (210) Pu Am Cm (244) (243) (247) 66 67 68 69 70 71 Dy Ho Er Tm Yb Lu Bk (247) 164.9303 167.26 98 99 100 Cf Es Fm (251) (252) (257) 168.9342
102 Md No
(258) (259) 36 Kr 131.29
86 65 162.50 39.948 126.9045
85 I Tb 158.9253
97 18 Ar 83.80 (266) Eu
Sm 151.964 Gd
150.36 10 79.904
53 Mt 62 196.96655 30 Si 109 Rf 195.078 20.1797 O 13 54.93805
43 58 Lanthanides 26 Ne N 26.98154
22 F C Al 21 1.00794
9 4.002602 8 10.811 24.3050
20 7 B Periodic T le of the Elements
ab 12 6 2 He 174.967
103 Lr (262) 54 Xe
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This note was uploaded on 01/10/2010 for the course CHEM 102a taught by Professor Hanusa during the Spring '06 term at Vanderbilt.
- Spring '06