Download Dec. 15 , 2012, 9:00 am – noon - Dr. K. Brown

University of Saskatchewan
Department of Chemistry
CHEMISTRY 112.3
Final Examination (Dec. 15th, 2012, 9:00 am – noon)
Family Name (please print carefully!)____________________________________________
Given Name (please print carefully!)_____________________________________________
Student Number
Signature___________________________________
Please indicate your section with an “X” in the list column:
Section 01
MWF 8:30 am
Section 03
MWF 9:30 am
Section 05
TTh 10:00 am
Section 97
Muenster
Section C11
Melfort
Section C15
Prince Albert
Dr. K. Brown
Dr. S. Urquhart
Dr. R. Scott
Dr. A. Szmigielski
Dr. A. Szmigielski
Dr. R. Catton
INSTRUCTIONS - PLEASE READ THIS FIRST!
a. This is a closed-book examination. A data-sheet with a Periodic Table accompanies this examination paper;
no other paper (or device) containing information relevant to this exam is permitted.
b. Simple scientific calculators (maximum two-line display) are permitted; graphing calculators, PDA's,
electronic dictionaries, etc., are not.
c. This examination paper has 14 pages; ensure that your copy is complete.
d. Answer multiple choice questions in Section A by circling a response on this paper AND by filling in
the corresponding response on the blue opscan sheet USING ONLY A SOFT-LEAD PENCIL. No
deductions will be made for incorrect answer. Multiple answers will be treated as NO answer; if you change
your mind, erase carefully. In the event of a discrepancy between an answer on the examination paper and
on the computer sheet, the response on the opscan sheet will count.
e. Answer the questions in Section B on this examination paper. Show all work; this will be graded.
f. If you have not already done so, please fill out the top of this paper now, and write your name (legibly!)
and code your student number on the computer blue sheet in soft pencil.
g. You can use the backsides of the pages as scratch paper (more paper will be available on request).
Questions
Maximum Marks
Section A (Q1 – Q42)
Marks Earned
63
(1.5 marks each)
Section B
Total
B1
8
B2
9
B3
10
B4
10
100
1
PART A
1) The number of neutrons, protons, and electrons in 31P3- are:
A)
B)
C)
D)
E)
15 neutrons, 31 protons, 15 electrons
16 neutrons, 15 protons, 18 electrons
31 neutrons, 15 protons, 18 electrons
15 neutrons, 16 protons, 12 electrons
16 neutrons, 16 protons, 18 electrons
2) What is the atomic mass of 12C?
A) 6 amu
B) 12 amu
C) 12.011 amu
D) Cannot be known without weighing out 1.00 moles of 12C
E) Cannot be known without knowing the mass of individual protons and neutrons
3) What is the atomic mass of an element if 4.00 grams of it contains 2.98 x 1022 atoms?
A)
B)
C)
D)
E)
20.2 amu
80.8 amu
19.7 amu
8.08 amu
2.02 amu
4) Maprotiline has the following mass composition: C 86.59%, H 8.35%, N 5.05%.
The empirical formula of maprotiline is:
A) C7H8N3
B) C20H23N
C) C87H8N5
D) C3H3N
E) C14H14N
5) Choose the incorrect name formula combination:
A) Fe2O3 iron (III) oxide
B) H2SO3 sulfurous acid
C) NH4ClO3 ammonium chlorate
D) CaH2 calcium hydride
E) SiO2 silicon oxide
2
6) Given the following reactions:
Fe (s) + Br2 (g) Æ FeBr2 (s)
3 FeBr2 (s) + Br2 (g) Æ Fe3Br8 (s)
If each reaction gives an 82% yield, what mass of Fe3Br8 is produced from 1.00g Fe, assuming Br2 is in excess?
A) 4.81 g
B) 3.94 g
C) 2.65 g
D) 3.23 g
E) 2.57 g
7) Determine the mass percent of H in NH4Cl.
A) 19%
B) 7.5%
C) 14%
D) 3.7%
E) 1.9 %
8) Which statement below is true?
A) Metals gain electrons to have a positive charge
B) Metals gain electrons to have a negative charge
C) Metals lose electrons to have a positive charge
D) Nonmetals always lose electrons to have a positive charge.
E) Transition metals can gain 2 or more electrons to become metal ions.
9) How much Cl2(g), in grams, is required to produce 12.0 g CCl4 according to the following reaction,
assuming that methane gas (CH4) is in excess:
CH4 (g) + 4 Cl2 (g) Æ CCl4 (g) + 4 HCl (g)
A) 12.0 g
B) 5.53 g
C) 22.1 g
D) 1.38 g
E) 11.0 g
10) What is the answer with the correct number of significant figures of the following calculation:
75.032 + 2.3 +0.0046
10.2
A) 7.6
B) 7.57
C) 7.58
D) 7.578
E) 7.52
3
11) Titanium(IV) oxide (TiO2) is produced by the action of sulphuric acid on FeTiO3.
FeTiO3 (s) + H2SO4 (aq) Æ TiO2 (s) + FeSO4 (s) + H2O (l)
In a reaction, 8.00x103 kg of FeTiO3 yielded 3.67x103 kg of TiO2. What is the percent yield of the reaction?
A) 1.15%
B) 115%
C) 45.9%
D) 87.1%
E) 8.45%
12) To determine molarity of an HCl solution, a 0.2400 g sample of Na2CO3 is titrated with 23.04 mL of HCl
solution. What is the molarity of the HCl solution?
Na2CO3(s) + HCl(aq) → NaCl(aq) + H2O(l) + CO2(g)
(unbalanced reaction)
A) 0.0393 M
B) 0.0983 M
C) 0.1310 M
D) 0.1966 M
E) 0.3931 M
13) In which compound the oxidation state of carbon is +4?
A) CO2
B) CaCO3
C) CCl4
D) H2CO3
E) All of the above
14) Krypton gas in an 18.5-L cylinder exerts a pressure of 11.2 atm at 28.2 0C. How many grams of krypton are
present?
A) 8.38 g
B) 502 g
C) 702 g
D) 755 g
E) 777 g
15) Which gas occupies the largest volume at STP?
A) 2.5 g H2
B) 2.5 g Cl2
C) 2.5 g He
D) 2.5 g CO2
E) All have the same volume
4
16) What is the total pressure if 1.0 g of H2 and 5.0 g of He are mixed in a 5.0 L flask at 20oC? Assume both
species are ideal gases.
A) 3.6 atm
B) 2.4 atm
C) 6 atm
D) 8.4 atm
E) No way of knowing with information given
17) A 1.00 L flask is filled with 0.160 g of unknown gas at 743 mmHg and 25 0C. Calculate the molar mass and
identify the gas. The unknown gas is:
A) CO2
B) O2
C) Ne
D) He
E) can be any of the above
18) Oxygen gas, generated by the reaction
2 KClO3 (s) → 2 KCl (s) + 3 O2 (g)
is collected at 27.0 0C and fills a 2.00 L vessel at a pressure of 750 Torr. What is the amount (in mol) of KClO3
consumed in this reaction?
A) 0.0790 mol
B) 0.119 mol
C) 0.0534 mol
D) 0.0813 mol
E) 2.00 mol
19) How much heat is required to warm 1.50 kg of sand from 25 0C to 100 0C?
Given: specific heat capacity of sand, Cs = 0.84 J/g 0C
A) 6.33 x 104 J
B) 7.85 x 104 J
C) 8.30 x 104 J
D) 9.45 x 104 J
E) 10.8 x 104 J
20) How much heat is released by combustion of 177 mL of acetone (C3H6O)?
Given: the density of acetone is 0.788 g/mL and ΔHrxn = -1790 kJ/mol.
C3H6O(l) + 4 O2(g) → 3 CO2(l) + 3 H2O(g)
A) –4.30 x 103 kJ
B) –5.50 x 103 kJ
C) –6.61 x 103 kJ
D) –7.00 x 103 kJ
E) –7.89 x 103 kJ
5
21) Calculate ΔHrxn for the reaction:
Fe2O3(s) + 3 CO(g) → 2 Fe(s) + 3 CO2(g)
Using the following reactions and ΔH’s.
2 Fe(s) + 3/2 O2(g) → Fe2O3(s)
CO(g) + 1/2 O2(g) → CO2(g)
ΔH = − 824.2 kJ
ΔH = − 282.7 kJ
A) –51.1 kJ
B) +16.3 kJ
C) –16.3 kJ
D) –23.9 kJ
E) +23.9 kJ
22) A 31.1-g block of pure gold (Cs of gold = 0.128 J/g 0C) initially at 69.3 0C is submerged into 64.2 g of water
(Cs of water = 4.18 J/g 0C) at 27.8 0C. What is the final temperature of both substances at thermal equilibrium?
A) 28.0 0C
B) 28.4 0C
C) 28.8 0C
D) 32.2 0C
E) 33.5 0C
23) Arrange the following elements in order of decreasing first ionization energy (from highest to lowest):
Fluorine, Potassium, Magnesium, Phosphorus, Sulfur.
A) F > S > P > Mg > K
B) F > S > P > K > Mg
C) F > P > S > Mg > K
D) P > S > F > K > Mg
E) S > F > P > Mg > K
24) According to Hund's rule, which element is expected to contain unpaired electrons?
A) Sr
B) Zn
C) Ge
D) All of A, B, and C
E) None of A, B, or C
25) Which of the following atoms or ions is paramagnetic: Be, Na, Ne, S2-, B, Fe3+ ?
A) Be, S2-, Ne
B) Na, S2-, Fe3+
C) Fe3+, Na, Be
D) Na, B, Fe3+
E) B, Fe3+, S2-
6
26) Which of the following statements is correct with respect to the as-yet unknown element with the atomic
number 119? (Note: g orbitals wouldn’t be used until hypothetical element #121)
A) It will be a member of the alkali metal group (1A)
B) It will have a filled 7d subshell
C) It will likely have a first ionization energy greater than that of radon (Z=86)
D) It will be a noble gas
E) None of the above
27) A possible set of quantum numbers for the last electron added to complete the electron configuration of an
atom of selenium in its ground state is:
A)
B)
C)
D)
E)
n= 4;
n= 3;
n= 4;
n= 3;
n= 4;
l=0;
l=0;
l=1;
l=1;
l=2;
ml=0;
ml=+1;
ml=-1;
ml=+1;
ml=+2;
ms=+1/2
ms=-1/2
ms=+1/2
ms=-1/2
ms=-1/2
28) Which element has the following electron configuration? [Kr]5s24d105p4
A) Sn
B) Sb
C) Pb
D) Ge
E) Te
29) Which of the following orbitals cannot/does not exist?
A) 6s
B) 3p
C) 2d
D) 5g
E) 7f
30) Which of the following statements for a group 7A element, X, is true?
A) Reaction with a group 1A alkali metal (M) yields a compound with the formula MX2
B) Reaction with a group 2A alkaline earth metal (E) yields a compound with the formula E2X
C) Ion of element X has a -1 charge
D) Ion of element X has a -2 charge
E) Element X is relatively inert and does not react with other elements
7
31) What is the wavelength of an electron that is moving at a velocity of 680 m/s?
A) 5.8 x 10-1 m
B) 7.4 x 10-2 m
C) 7.4 x 10-4 m
D) 1.1 x 10-6 m
E) none of the above
32) Arrange the following isoelectronic ions in order increasing radius: Ca2+, S2-, Cl-. (Smallest to largest)
A) Ca2+< Cl- < S2B) Cl- < Ca2+< S2C) Ca2+< S2-< ClD) S2-< Cl- < Ca2+
E) Cl- < S2- < Ca2+
33) For the anion Te2-, which of the following statements is correct?
A) It is isoelectronic with Kr
B) It will combine with Al3+ to form the compound Al2Te3
C) It has 52 electrons
D) All of A, B and C are correct
E) None of A, B and C is correct
34) Which of the following descriptions is correct?
Given electronegativity values: Cs: 0.8 H: 2.1
Br: 2.8
N: 3.0
Cl: 3.0
O: 3.5
F: 4.0
A) CsF – polar covalent
B) Cl2 – ionic
C) NO – non-polar
D) HCl – polar covalent
E) BrCl – polar covalent
35) What is the formal charge on P in PCl5?
A) 5
B) 2
C) 1
D) 0
E) -1
36) Given the bond enthalpies below, compute the enthalpy change for the following chemical reaction:
NH3 (g) + Cl2 (g) Æ NH2Cl (g) + HCl (g)
Bond energies N-H (389 kJ/mol); Cl-Cl (243 kJ/mol); N-Cl (201 kJ/mol); and H-Cl (431 kJ/mol)
A) -393 kJ/mol
B) -1100 kJ/mol
C) +71 kJ/mol
D) +393 kJ/mol
E) 0 kJ/mol
8
37) A molecule has the formula ML2. Atom M is the central atom and the L-M-L bond angle is 117o. What are
the most likely electron groups?
A) Two bonds and no non-bonding pairs
B) Two bonds and one non-bonding pair
C) Two bonds and two non-bonding pairs
D) Two bonds and three non-bonding pairs
E) Three bonds an no non-bonding pairs
38) How many equivalent resonance structures does the ion NO3- have?
A) 1
B) 2
C) 3
D) 5
E) 8
39) Which of the following molecules has a net dipole moment?
A) BF3
B) BeCl2
C) CO2
D) CH4
E) NH3
40) What intermolecular force is the most important between CH3Cl molecules in a pure sample of the
compound in the liquid phase?
A) Ion – ion
B) Ion – dipole
C) Dipole – dipole
D) Dispersion
E) Covalent bonding
41) Which of the following compounds has the highest boiling point?
A) CH4
B) H2O
C) LiF
D) CH3Cl
E) N2
42) Ethanol (C2H5OH) has a heat of fusion of 5.01 kJ/mol. How much heat is required to melt 137 g of ethanol.
A) 1.70 x 103 kJ
B) 129 kJ
C) 686 kJ
D) 5.01 kJ
E) 14.9 kJ
9
PART B
Use the available space to answer the following questions.
B1. (8 marks)
Mg (s) will react with aqueous HCl to generate H2 gas and magnesium chloride.
(a) Write the balanced equation for this reaction (2 marks).
(b) If one started with 10.0 g of Mg and 25.0 mL of a 1.00 M solution of HCl, how many moles of H2 gas would
be evolved? (4 marks)
(c) Assuming STP conditions, what would the volume of this much H2 gas be? Assume H2 gas behaves as an
ideal gas. (2 marks)
10
B2. (9 marks)
One of the main emission wavelengths of Helium-Neon lasers is an emission line at 633 x 10-9 m.
(a) What is the frequency of light at this wavelength? (2 marks)
(b) What is the energy of a single photon at this wavelength? (3 marks)
(c) How many photons at this wavelength would be required to raise the temperature of 10.0 g of water at
25.0oC by 1.0oC? Assume all the light is absorbed by the water.
Given: the specific heat capacity of water is 4.18 J/goC (4 marks)
11
B3. (10 marks)
(a) Given the Pauling electronegativity values below indicate whether the following bonds are ionic, covalent
polar or covalent non-polar: (3 marks)
EN values: Ca: 0.8
H: 2.1
C: 2.5
Br: 2.8
Cl: 3.0
O: 3.5
F: 4.0
i) a Ca-F bond
ii) a C-Br bond
iii) a C-Cl bond
(b) Draw a Lewis dot structure for the following molecules and indicate whether they are polar or non-polar.
(3 marks) The central atom has been underlined in each molecule.
i) CF4
ii) CF3Cl
iii) CF3(OH)
(c) Indicate the likely order of boiling points of the above three compounds (from lowest to highest), taking into
account intermolecular forces present in each liquid. (2 marks)
(d) Which of the above liquids would have the highest surface tension? (2 marks)
12
B4. (10 marks)
Fill in the blanks in this table. The central atom for each species has been underlined. If there are resonance
structures, just show one of them. 1 mark for each blank.
Species
Best Lewis Dot Structure
Resonance
structures
possible?
(Y/N)
Formal
Charge of
Central
Atom
No
0
Electron Group
Geometry
Molecular
Group Geometry
(Shape)*
BrF5
XeF2
No
0
HCN
No
0
linear
PO3Trigonal planar
Trigonal planar
0
* What is the shape of the molecule? Either use the correct terminology for the geometry or provide a drawing.
In the case of a drawing, it must be unambiguous, with important bond angles indicated.
THE END.
13
1
1A
1
1.00794
2
2A
3
4
H
18
8A
Periodic Table of the Elements
13 14 15
3A 4A 5A
5
6
7
16
6A
8
17 2
He
7A 4.00260
9
10
Li
Be
B
C
N
O
F
Ne
6.941
9.01218
10.811
12.011
14.0067
15.9994
18.9984
20.1797
11
12
13
14
15
16
17
18
4
5
6
7
8
9
10
11
12
Si
P
S
24.3050
3
Al
22.9898
Na Mg
26.9815
28.0855
30.9738
32.066
35.4527
39.948
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
K
Ca Sc Ti
Cr Mn Fe Co
Ni
Cu Zn Ga Ge As
Se
Br Kr
39.0983
40.078
44.9559
47.88
50.9415
51.9961
54.9381
55.847
58.9332
58.693
63.546
65.39
69.723
72.61
74.9216
78.96
79.904
83.80
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
Rb Sr
V
Cl Ar
Ag Cd In Sn Sb
Te
I
Xe
85.4678
87.62
88.9059
Y Zr Nb Mo Tc Ru Rh Pd
91.224
92.9064
95.94
(98)
101.07
102.906
106.42
107.868
112.411
114.818
118.710
121.757
127.60
129.904
131.29
55
56
57
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
Cs Ba La Hf Ta W
Re Os
Ir
Pt
Au Hg Tl Pb Bi
132.905
137.327
138.906
178.49
180.948
183.84
186.207
190.23
192.22
195.08
196.967
200.59
87
88
89
104
105
106
107
108
109
110
111
112
Fr Ra Ac Rf Db Sg
(223)
226.025
227.028
(261)
Po At Rn
204.383
207.2
208.980
(209)
(210)
(222)
66
67
68
69
70
71
Bh Hs Mt
(262)
(263)
(262)
(265)
(266)
(269)
(272)
(272)
58
59
60
61
62
63
64
65
Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
140.115
140.908
144.24
(145)
150.36
151.965
157.25
158.925
162.50
164.930
167.26
168.934
173.04
174.967
90
91
92
93
94
95
96
97
98
99
100
101
102
103
Th Pa
232.038
231.036
U
238.029
Physical Constants
Constant
Atomic mass unit
Avogadro number
Gas Constant
Np Pu Am Cm Bk Cf Es Fm Md No Lr
237.048
(244)
Symbol
u
NA
R
Molar volume of an ideal gas at STP
Planck constant
Vm
h
Speed of light in a vacuum
Rydberg Constant
Electron mass
Some SI Derived Units
Physical Quantity
Force
Energy
Pressure
c
RH
me
Unit
Newton
Joule
Pascal
(243)
(247)
(247)
(251)
(252)
(257)
(258)
(259)
(260)
Value
1.6605 × 10–27 kg
6.0221 × 1023 mol–1
0.082058 L atm mol–1K–1
8.3145 J K–1 mol–1
62.364 L mmHg mol–1 K–1
22.414 L mol–1
6.6261 × 10–34 J s
6.6261 × 10-34 m2kg/s
2.9979 × 108 m s–1
2.179 × 10–18 J
9.109 × 10–31 kg
Symbol
N
J
Pa
Definition
kg m s–2
kg m2 s–2
N m–2 = kg m–1 s–2
P = 1 atm = 760 torr = 760 mmHg = 101.325 kPa, Temperature = 0 ºC = 273.15 K
h
h
Heisenberg Uncertainty Principle: Δx ⋅ Δp ≥
, de Broglie's wavelength of particles: λ =
4π
m ⋅u
STP Conditions:
14