University of Saskatchewan
Department of Chemistry
CHEMISTRY 112.3
Midterm Examination (Sat. Oct 23th, 2010, 10:00 AM – 12:00 noon)
Family Name (please print carefully!)____________________________________________
Given Name (please print carefully!)_____________________________________________
Student Number
Signature___________________________________
Please indicate your section:
Section 01
Section 03
Section 05
Section 91
Section 97
Section C11
Section C15
MWF 8:30 am
MWF 9:30 am
TTh 10:00 am
TTh 8:30 am
Muenster
Melfort
Prince Albert
Dr. K. Brown
Dr. I. Burgess
Dr. A. Baranski
Dr. L. Wilson
Dr. A. Szmigielski
Dr. A. Szmigielski
Dr. P. Ahiahonu
INSTRUCTIONS - PLEASE READ THIS FIRST!
a) This is a closed-book examination. A data-sheet with a Periodic Table can be found as the last page
of this examination paper (you can remove this page from the booklet for convenience).
b) Simple scientific calculators (maximum two-line display) are permitted; graphing calculators, PDA's,
electronic dictionaries, etc. are not. No equations should be stored in memory of electronic devices.
c) This examination paper has 10 pages. To ensure your copy is complete and to become familiar with the
questions, please read through the entire examination before you answer any questions.
d) You can use the backsides of the 10 pages as scratch paper (more paper will be available on
request).
e) A total of 100 marks can be obtained. Each of the 40 questions will be weighted with 2.5 marks. You
should spend on average 3 min. on each question. ONLY one answer per question is correct!
f) Please fill out the top of this paper and on the blue sheet, print your name and code your student
number in soft pencil.
g) On the blue sheet, after your name, write in brackets the version of the exam (A or B) as shown on
the top of this paper.
h) Answer multiple choice questions 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 answers. 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.
i) HAND-IN ALL your material: question sheet, computer sheet, and scratch paper (if you use one).
1
1. Knowing that 1L = 1 dm3, what is the volume of a box (in L) that is 1.0 cm in length, 0.500 m in height and
2.0 cm in width? The volume of a box is height × width × length.
A. 0.010 L
B. 0.10 L
C. 1.0 L
D. 10 L
E. 1.0×102 L
2. Which of the following does not describe a physical change?
A. A penny turns green if left outside for a long time.
B. A rainbow appears after a brief shower.
C. Frost forms on the grass after a chilly autumn night.
D. Solid gold liquefies at temperatures over 1060oC.
E. An open glass of water evaporates if left outside for a long time.
3. What is the correct formula for the chlorite ion?
A.
B.
C.
D.
E.
Cl–
ClO–
ClO2–
ClO3–
ClO4–
4. What is the mass percent of hydrogen in ethanol if the molecular formula for ethanol is (C2H6O)?
A.
B.
C.
D.
E.
13%
35%
67%
52%
None of the above.
5. Which of the following is not an example of a molecular element?
A.
B.
C.
D.
E.
O2
P4
S8
They are all molecular elements.
None of them are molecular elements.
6. Phosgene was a toxic gas used in the First World War and is a molecular compound that contains only
carbon, chlorine and oxygen atoms. If a 10.0 g sample of phosgene is found to contain 1.21 g of carbon and
1.62 g of oxygen, what is the empirical formula of phosgene?
A.
B.
C.
D.
E.
COCl
C2OCl
CO2Cl
COCl2
C2O2Cl
2
7. The recommended daily intake of sodium is no more than 2.4 g. Assuming that sodium chloride is the only
source of sodium in your diet, what is the maximum mass of sodium chloride you can consume and still be
below the recommended guidelines?
A.
B.
C.
D.
E.
6.1g
0.94g
3.9g
0.25g
Not enough information is provided to answer the question.
8. What is the correct formula for potassium dihydrogen phosphate hexahydrate?
A.
B.
C.
D.
E.
KHPO4 ·6H2O
K2HPO4·5H2O
KH2PO4·5H2O
K2HPO4·6H2O
None of the above
9. Balance the following reaction and provide the correct stoichiometric coefficients.
a CO2 (g) + b CaSiO3 (s) + c H2O (l)  d SiO2 (g) + e Ca(HCO3)2 (aq)
A. a = 1; b = 1; c = 1; d = 1; e = 1
B. a = 1; b = 2; c = 2; d = 1; e = 1
C. a = 2; b = 2; c = 1; d = 2; e = 2
D. a = 2; b = 1; c = 1; d = 1; e = 1
E. None of the above.
10. What is the correct name for the compound, Cr(NO2)3?
A.
B.
C.
D.
E.
chromium trinitrogen oxide
chromium (III) nitrate
chromium nitrogen dioxide
chromium (III) nitrite
None of the above.
11. The correct symbolic notation for the isotope of chlorine that has 19 neutrons is:
A.
17
19
B.
19
17
C.
17
36
D.
36
17
E.
17
17
Cl
Cl
Cl
Cl
Cl
3
12. In 2.6 mols of Na2PO4 there are:
A. 2.6 mols of oxygen atoms
B. 10.4 mols of oxygen atoms
C. 2.6 mols of sodium atoms
D. 2.6 mols of platinum atoms
E. none of these is correct
13. One of the first experimental pieces of evidence for the existence of atoms is now known as:
A. the law of conservation of momentum
B. the law of conservation of energy
C. the law of definite proportions
D. the law of mass action
E none of the above
14. The number of electrons, protons and neutrons (in that order) in 32S2– is:
A. 2, 16, 16
B. 16, 16, 16
C. 18, 16, 16
D. 18, 16, 18
E. cannot tell from given information
15. Which of the following does not correspond to 1 mol:
A. 6.022 × 1023 protons
B. 55.85 g Fe
C. 12.011 g C
D. 32.38 g Zn
E. 6.022 × 1023 CH4 molecules
16. The electrical charge on a strontium (Sr) ion in its compounds is:
A. +1
B. +2
C. +3
D. –1
E. –2
4
17. In the following redox reaction the oxidizing agent is:
Cr2O72–(aq) + 6Fe2+(aq) + 14H+(aq)  2Cr3+(aq) + 6Fe3+(aq) + 7H2O(l)
A. Cr2O72–(aq)
B. Fe2+(aq)
C. Cr3+(aq)
D. H2O(l)
E. H+ (aq)
18. The volume of 0.050M NaOH solution needed to titrate 25mL of 0.10M HNO3 solution is:
A. 12.5 mL
B. 18 mL
C. 25 mL
D. 40 mL
E. 50 mL
19. A strong acid:
A. dissociates partially in aqueous solution
B. does not dissociate at all in aqueous solution
C. dissociates completely in aqueous solution
D. reacts only with strong bases
E. none of the above
20. Nitric acid, HNO3, is a strong oxidizing agent. Which of the following is least likely to be a product of a
redox reaction involving nitric acid?
A. N2O
B. NO
C. NO2
D. N2O4
E. N2O5
21. What is the limiting reagent in the reaction of one mole of O2 (g) with one mole of NH3(g) ?
NH3 (g) + O2 (g)  N2 (g) + H2O (l) (unbalanced!)
A. NH3(g)
B. O2(g)
C. N2(g)
D. H2O
E. all reactants are in stoichiometric proportions
5
22. Given the reaction:
Cr2O72–(aq) + 6Fe2+(aq) + 14H+(aq)  2Cr3+(aq) + 6Fe3+(aq) + 7H2O(l) (balanced!)
How many moles of Cr3+(aq) are produced by allowing 6 moles of Cr2O72–(aq), 12 moles of Fe2+(aq) and 70
moles H+(aq) to react? Note that this reaction occurs with 100% yield.
A. 4 mol
B. 24 mol
C. 6 mol
D.12 mol
E. none of the above
23. In some chemical reaction the actual yield is significantly lower than the theoretical yield. What could be a
plausible cause of the low actual yield?
A. One of the reactants is used up before the others
B. Vigorous stirring of the reacting solution breaks some molecules apart
C. A theory never really works in practice
D. The reactants may participate in a separate simultaneous reaction forming a by-product
E. none of the above
24. 0.337 moles of PCl3 is produced from the reaction of solid elemental phosphorous, P(s), with excess
chlorine gas. Determine the mass of phosphorous required for this reaction if the yield is 30%?
A. 34.8 g
B. 69.6 g
C. 10.4 g
D. 20.9 g
E. 104 g
25. Which of the following represents a 0.100 M KCl solution?
A. 100 g KCl in 1.00 L of solution
B. 1000 mL of solution containing 74.6 g KCl
C. 7.46 mg KCl per mL of solution
D. 5.00 L of solution containing 373 g KCl
E. none of the above
26. Given the following unbalanced chemical reaction, what volume of 0.650 M K2CrO4 is required to
completely precipitate the silver ions in 415 ml of 0.186 M AgNO3 as Ag2CrO4 (s).
AgNO3 (aq) + K2CrO4 (aq)  Ag2CrO4 (s) + KNO3 (aq)
A. 178 ml
B. 119 ml
C. 59.4 ml
D. 593 ml
E. 29.7 ml
6
27. When equal volumes of 0.2 M solutions are mixed, which of the following combinations will form a
precipitate?
A. CuCl2(aq) + NH4NO3(aq)
B. MgSO4(aq) + K2CO3(aq)
C. Na2S(aq) + LiClO4 (aq)
D. FeCl3(aq) + CuSO4(aq)
E. none of the above
28. Identify the major ions present in an aqueous solution of Li2CO3.
–
A. Li2+, CO3
2–
B. Li2+, CO3
2–
C. Li+, CO3
4–
2–
D. Li+, C , O
4+
2–
E. Li+, C , O
29. The distinguishing characteristic of all electrolyte solutions is that they
A. contain molecules
B. conduct electricity
C. react with other solutions
D. always contain acids
E. none of the above
30. An aqueous solution of acetic acid (weak acid), CH3COOH, reacts with an aqueous solution of sodium
carbonate (strong electrolyte) to produce an aqueous solution sodium acetate (strong electrolyte), carbon
dioxide gas and water. Which of the following represents the net ionic equation of this reaction?
A. 2CH3COO–(aq) + 2H+(aq) + Na2CO3(aq)  2CH3COONa(aq) + CO2(g) + H2O(l)
B. 2CH3COOH(aq) + Na2CO3(aq)  2CH3COONa(aq) + CO2(g) + H2O(l)
C. 2H+(aq) + CO32–(aq)  CO2(g) + H2O(l)
D. 2CH3COO–(aq) + 2H+(aq) + 2Na+(aq) + CO32–(aq)  2Na+(aq) + 2CH3COO–(aq) + CO2(g) + H2O(l)
E. 2CH3COOH(aq) + CO32–(aq)  2CH3COO–(aq) + CO2(g) + H2O(l)
31. A certain amount of argon gas occupies 2.50 L at 250 ºC and 1.57 atm pressure. What will be the volume of
the same amount of argon at 250 K and 157 torr pressure?
A. 2.50 L
B. 9.08 L
C. 39.8
D. 0.688 L
E. 19.0 L
7
32. Silver (I) Oxide decomposes to form 4.58 L of O2 (g) at 745 mm Hg at 308 K. How much silver (I) oxide
decomposed?
2 Ag2O (s)  4 Ag (s) + O2 (g)
(balanced)
A. 146 g
B. 36.4 g
C. 82.3 g
D. 0.178 g
E. none of the above
33. Hydrogen gas produced during the following chemical reaction
Fe (s) + 2 HCl (aq)  FeCl2 (aq) + H2 (g)
was collected over water at STP and became saturated with water vapour. The vapour pressure of water is 4.58
mm Hg at these conditions. What is the partial pressure of hydrogen?
A. 4.58 mm Hg
B. 760 mm Hg
C. 765 mm Hg
D. 755 mm Hg
E. Insufficient information is provided for the calculation
34. The empirical formula of a gaseous fluorocarbon is CF2. Determine the molecular formula of this compound
knowing that 1.55 g of the compound occupies 0.174 L at STP.
A. CF2
B. C2F4
C. C3F6
D. C4F8
E. none of the above
35. Which statement concerning the kinetic theory of gases is false?
A. Collisions between gas particles result in a loss of energy
B. The frequency of collisions depends on the temperature
C. The size of the gas particle is negligibly small
D. Gas particles have finite masses
E. none of the above
36. Which statement is true for samples of H2 (g), O2 (g), and CO2 (g) at the same temperature and pressure.
(Assume that these gasses behave as ideal gasses.)
A. The molar volume of each gas is the same
B. If all three samples have the same mass, then their volumes must be the same
C. Molecules of each gas move with the same average velocity
D. The density of each gas is the same
E. All of the above statements are false
8
37. A mixture of He and Cl2 has partial pressures 0.300 atm and 0.700 atm respectively. Knowing that the mass
of Cl2 in the mixture is 1.00 g calculate the number of He atoms?
A. 3.64×1021
B. 1.38×1022
C. 3.98×1022
D. 7.28×1021
E. not enough information to determine
38. Consider samples of H2, SO2, CH4 and NH3 each at identical conditions of temperature and pressure. Which
gas has the density higher than air at the same temperature and pressure (i.e. which one is “heavier” than air)?
Air composition: N2 ‒ 78% volume, O2 ‒ 21% volume, other gases (mainly Ar) ‒ 1% volume.
A. H2
B. SO2
C. CH4
D. NH3
E. Not enough information to determine
39. Consider a gaseous mixture of H2, SO2, CH4 and NH3. Which molecules will move with the highest average
velocity at a given temperature?
A. H2
B. SO2
C. CH4
D. NH3
E. All molecules move with the same average velocity
40. Under which conditions would helium (He) gas show the largest deviation from the ideal gas behavior?
A.
B.
C.
D.
E.
at 1 atm and 1000 K
at STP
at 100 Pa and 10 K
at 100 bar and 10 K
He would behave as an ideal gas in all these cases
The End
9
1
1A
1
18
Periodic Table of the Elements
8A
2
2
13
14
15
16
17
1.00794
2A
3A
4A
5A
6A
7A
4.00260
3
4
5
6
7
8
9
10
H
He
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
Na Mg
3
4
5
6
7
8
9
10
11
12
4B
5B
6B
7B
8B
8B
8B
1B
2B
Si
P
S
24.3050
3B
Al
22.9898
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
Y
V
Cl Ar
Zr Nb Mo Tc Ru Rh Pd
Ag Cd In Sn Sb
Te
I
Xe
85.4678
87.62
88.9059
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
Bi
Po
208.980
(209)
Cs Ba La Hf Ta
W
Re
Os
Ir
Pt
Au Hg Tl Pb
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
114
116
118
(287)
(289)
(293)
Fr Ra Ac Rf Db Sg
(223)
226.025
227.028
(261)
204.383
207.2
At Rn
(210)
(222)
Bh Hs Mt
(262)
(263)
(262)
(265)
(266)
(269)
(272)
(272)
58
59
60
61
62
63
64
65
66
67
68
69
70
71
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
Np Pu Am Cm Bk Cf Es Fm Md No Lr
237.048
Constant
Atomic mass unit
Avogadro number
Gas Constant
Molar volume of an ideal gas at STP
Planck constant
Speed of light in a vacuum
Rydberg Constant
Electron mass
(244)
(243)
(247)
(247)
(251)
(252)
(257)
(258)
(259)
(260)
Physical Constants
Symbol
Value
u
1.6605 × 10-27 kg
NA
6.0221 × 1023 mol-1
R
0.082058 L atm mol-1K-1
8.3145 J K-1 mol-1
62.364 L mmHg mol-1 K-1
Vm
22.414 L mol-1
h
6.6261 × 10-34 J s
c
2.9979 × 108 m s-1
RH
2.179 × 10-18 J
me
9.109 × 10-31 Kg
Some SI Derived Units
Physical Quantity
Unit
Symbol
Definition
Force
Newton
N
kg m s-2
Energy
Joule
J
kg m2 s-2
-2
Pressure
Pascal
Pa
N m = kg m-1 s-2
STP Conditions: P = 1 atm = 760 Torr = 760 mmHg = 101.33 kPa = 1.0133 bar
Temperature = 0 ºC = 273.2 K
10