1
Chemistry 6
Final Exam
Name_____________________________________
1.
a. (12 points) Using the following information, calculate the lattice energy for KCl.
Ionization Potential of K = 420 kJ/mole
Electron Affinity of Cl = -350 kJ/mole
Standard Heat of Formation of KCl = -440 kJ/mole
Standard Heat of Sublimation of K = 60 kJ/mole
Bond Dissociation energy of Cl2 = 250 kJ/mole
b. (12 points) Order the following ionic solids in terms of increasing bond energy.
Note that no calculations are necessary and only a very brief (one or two lines)
explanation is needed.
MgO, NaF, CaF2, KCl
SECTION II.
1.
A first order reaction has a half-live of 26.2 minutes. At what time will the reaction be
90% complete?
a. 8.7 min.
2.
c. 262 min.
d. 13.1 min.
e. 26.2 min.
The rate constant for the reaction 2HI → H2 + I2 is 1.22 x 10-6M-1 s-1 at 575 K and
1.16 x 10-3 M-1s-1 at 700 K. What is the activation energy for this reaction?
a. 186 kJ mole-1
3.
b. 87 min.
b. 1000 kJ mole-1
c. 81 kJ mole-1
d. 47 kJ mole-1
The reaction between carbon monoxide and chlorine to form phosgene,
Cl2 + CO → Cl2CO, occurs by the following mechanism:
Cl2 + M ⇔ 2Cl + M (fast equilibrium, K1)
Cl + CO + M ⇔ ClCO + M (fast equilibrium, K2)
ClCO + Cl2 → Cl2CO + Cl (slow, k3).
2
Which one of the following rate laws is consistent with this mechanism?
a. Rate = k [Cl2] [CO]1/2
b. Rate = k [Cl2] [CO]2
d. Rate = k [Cl2]1/2 [CO]
4.
c. Rate = k [Cl2] [CO]
e. Rate = k [Cl2]3/2 [CO]
The rate constant for the hypothetical reaction A + B → C is 9.2 s-1 at 500 K. How
long will it take for 95% of the materials to react?
a. 27.6 s
5.
b. 9.2 s
c. 0.67 s
e. 0.15 s
Arrange the following atoms/ions in order of increasing ionization potential: F, Na,
B+ , Ne- and Ne.
a. B+ , Ne-, Na, F, Ne
b. Ne-, Na, F, Ne, B+
d. B+ , Ne, Na, Ne-, F
6.
d. 0.33 s
c. B+ , Ne, Na, F, Ne-
e. Na, B+ , Ne-, Ne, F
Which of the elements/ions in the following series are not isoelectronic?
Ar, Cl-, K+ , Ca+ , Cr3+, S2-, Mg2+
a. S2-
b. Ar, Cl-, K+
c. Ca+ , S2-, Cr3+
d. Ca+ , Cr3+, Mg2+
e. they are all isoelectronic
7.
Which of these elements, Li, Ti, Na, Fe, K, has the smallest atomic radius?
a. Li
8.
b. Na
c. K
e. Fe
The maximum wavelength capable of ejecting an electron from potassium is 600 nm.
What is the kinetic energy of an electron ejected from potassium by a photon of
wavelength 350 nm?
a. 5.68 x 10-19 J
b. 3.31 x 10-19 J
d. 1.02 x 10-19 J
9.
d. Ti
c. 2.36 x 10-19 J
e. 4.32 x 10-19 J
What is the ideal geometry of BrF3?
a. planar
b. linear
c. tetrahedral
d. octahedral
e. trigonal bipyramidal
3
10. Which of the following molecules has a dipole moment?
b. NF3
a. SF6
11.
c. BF3
d. CO2
What is the ionization energy of Li2+?
a. 1.95 x 10-17 J
b. 2.17 x 10-18 J
d. 6.54 x 10-18 J
12.
b. CN
c. CN-
b. 91.5 nm
c. 11.4 nm
b. sp2
d. 7.6 nm
d. dsp3
c. sp
e. 22.9 nm
e. d2sp3
b. one radial & one angular node c. two radial & no angular nodes
d. no radial & two angular nodes
e. three radial & no angular nodes
What is the energy corresponding to the second ionization potential of He?
a. 5.44 x 10-19 J
b. 1.09 x 10-18 J
d. 4.35 x 10-18 J
17.
e. O2
The 3dxy orbital for the hydrogen atom has
a. no nodes
16.
d. NO+
What is the hybridization of the central atom (oxygen) in the OF2 molecule?
a. sp3
15.
e. 4.34 x 10-19 J
The ionization energy of Be3+ is 3.47 x 10-17J. What is the wavelength of the n = 1
to n = 2 transition in this ion?
a. 46.0 nm
14.
c. 8.72 x 10-18 J
Which of the following molecules/ions has the shortest bond length?
a. CN+
13.
e. CF4
c. 2.17 x 10-18 J
e. 8.70 x 10-18 J
What is the actual geometry of the ClF5 molecule?
a. bent
b. square pyramidal
c. planar
d. pyramidal
e. trigonal
4
18. Predict the order of increasing bond strengths for the F2, F2+ , F2- series of
molecules/ions.
a. F2, F2+ , F2-
b. F2+ , F2 , F2d. F2, F2-, F2+
19.
e. F2-, F2, F2+
What is the energy of an electron whose wavelength is equal to that of a photon with
energy equal to 8.00 x 10-19 J?
a. 8.00 x 10-19 J
b. 3.84 x 10-24 J
d. 1.60 x 10-19 J
20.
Which of the following sets of quantum numbers is wrong (given as n, l, ml, ms)?
c. 3, 3, -1, -1/2
d. 2, 0, 0, -1/2
e. 2, 1, 1, 1/2
For the concentration cell, Cu | Cu2+ (1.00 x 10-7 M) || Cu2+ (1.00 M) | Cu, what is
the cell emf?
a. -0.414 V
22.
c. 3.00 x 10-10 J
e. 8.70 x 10-5 J
a. 2, 1, 0, 1/2 b. 3, 2, -1, -1/2
21.
c. F2-, F2+ , F2
b. -0.207 V
c. 0.207 V
d. 0.414 V
e. 0 V
An example of an ionic molecule is
a. CsF
b. H2
c. CO
d. HI
e. BF3
SECTION III.
1. a. (10 points) Based on the data shown below, determine the order of the reaction with
respect to each of the reactants, i.e., find a,b and c. The overall reaction is
H2 + Br2 → 2HBr
and the rate law may be written as Rate = k [H2]a [Br2]b [HBr]c.
5
Rate, 10-3 M / s
[H2], M
[Br2], M
[HBr], M
0.10
0.10
1.0
1.5
0.10
0.40
1.0
24.0
0.20
0.10
1.0
3.0
0.10
0.10
2.0
0.75
b. (10 points) Use the data in the table in part a to find a numerical value for the rate
constant.
2.
(20 points / 4 points each) Write Lewis Dot Structures for each of the following
molecules and note both the ideal geometry and the hybridization of the central atom.
a. SF2
b. XeF2
c. BF3
d. CO32- (one resonance structure is sufficient)
e. IO4-
3.
a. (8 points) List the following species in terms of increasing bond length. Very
briefly, describe the logic you used to reach this ordering (one or two lines).
O2, O2+ , O2-, O22b. (12 points / 3 each) For each pair of molecules/ions, select the one with the
greatest bond energy.
i) B2, B2+
ii) NO, NF
iii) F2, F2iv) CN, N2
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4.
a. (7 points) Draw appropriate resonance structures for acetic acid and the acetate
ion. The skeletal structures are
O
H3 - C - C - O-H
(acetic acid)
O
H3 - C - C - O(acetate)
b. (13 points) Use these resonance structures to discuss differences (if any) in the
C-O bonds both within each molecule. Then compare the C-O bonds in the two
molecules. Try to be as brief as possible.
5.
a. ( 12 points) Electrons may be ejected from the surface of Mo by photons of
wavelength 274 nm or less. What is the wavelength of an electron ejected by
means of 200 nm radiation from the surface of Mo?
b. (8 points) Calculate the wavelength corresponding to the series limit for the n=5
series of the He+ ion.
6.
a. (8 points) Identify the nature of the molecular spectrum shown below. Very
briefly, explain your reasoning.
30000 cm-1
40000 cm-1
b. (12 points) Write electronic configurations for each of the following. Then order
the species in terms of increasing electron affinity.
i) Oii) I
iii) Kr+
iv) Se-
7
kBoltzmann = 1.38 x 10-23 J/K
[A] = [A]o e-kt
R = 8.31 J/mole - K
1 = 1 + kt
[A] [A]o
k = P πd2ve-Ea/RT
k = Ae-Ea/RT
v = (8RT ) 1/2
πM
t1/2 = 0.693
k
t1/2 = 1
[A]ok
E=-
E = hν
c = λν
E=-
109678cm -1• Z
n
2.17 x 10 -18 J • Z
n
2
2
2
2
p=h/λ
∆x • ∆p ≥ h
2
p = mv
∆E = R( 1 - 1 )
n2f n2i
p2
K.E. = 1 mv 2 =
2
2m
E = φ + 1 mv 2
2
Vsphere= 4 πr3
3
R = 109678cm-1 • Z2
c = 3 x 108m s-1
e = 1.60 x 10-19Coulombs
1Å = 10-8cm
1nm = 10-9m
melectron = 9.11 x 10-31kg
NA = 6.02 x 1023 mole-1
h = 6.62 x 10-34J•s
1J =5.03 x 1022cm-1
ao= 0.530Å
ε = ε0 -
0.0592
[products]
log
n
[reactants]
Q=I•t
1F = 96500 C