University of Saskatchewan
Department of Chemistry
CHEMISTRY 112.3
Midterm Examination (Sat. Oct 27th, 2007, 10:00 AM – 12:00 noon)
Family Name (please print carefully!)____________________________________________
Given Name (please print carefully!)_____________________________________________
Signature___________________________________
Student Number
Please indicate your section:
Section 01
Section 03
Section 05
Section 07
Section 91
Section 97
Section C11
Section C15
Section C51
MWF 8:30 am
MWF 9:30 am
MWF 11:30 am
TTh 10:00 am
TTh 8:30 am
St. Peter's College
Cumberland Regional College
Woodland Institute - Prince Albert
North West Regional College - North
Battleford
Dr. P. Ahiahonu
Dr. I. Burgess
Dr. J. Müller
Dr. K. Brown
Dr. L. Wilson
Dr. A. Szmigielski
Dr. A. Szmigielski
Dr. R. Zee
Dr. S. Brunet
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.
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.
c) This examination paper has 11 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) Use the examination booklet as SCRATCH PAPER.
e) Please fill out the top of this paper and the examination booklet.
f) On the blue sheet, print your name (legibly!) and code your student number
in soft pencil.
g) Check that your answers match on blue sheet and exam paper before handing
them in.
h) A total of 100 marks can be obtained. Each of the 50 questions will be weighted
with 2 marks. You should spend on average 2 min 24 seconds on each question.
ONLY one answer per question is correct!
i) HAND-IN ALL your material (question sheet, computer sheet, and scratch
paper).
1
1. How many significant figures are appropriate to show in the result for the following
40.88 − 2.0455
mathematical operation?
0.0010(6.77)
A) 1
B) 2
C) 3
D) 4
E) 5
2. The acceleration due to gravity at a location is 32.2 ft s-2, what is its numerical value if
it is expressed in terms of m h-2? (1 ft = 30.48 cm)
A) 3.53 x 104 m h-2
B) 4.17 x 108 m h-2
C) 3.95 x 109 m h-2
D) 1.27 x 108 m h-2
E) 0.456 x 108 m h-2
3. A uniform sphere has a radius (R) of 1.80 cm and a density of 2.041 g cm-3, what is the
value of its mass in grams (use correct number of significant figures)?
4
Given: volume of sphere = π R3 (with π = 3.1416)
3
A) 49.9 g
B) 49.86 g
C) 50 g
D) 49.860 g
E) None of the above.
4. What is the correct name for the compound Cl2O5?
A) dichlorine oxide
B) chlorine(V) oxide
C) dichlorine pentoxide
D) chlorine pentoxide
E) None of the above.
5. What is the correct name for the compound Mn3(PO4)2?
A) Manganese phosphate
B) Manganese(II) phosphate
C) Manganese(III) diphosphate
D) Manganese(II) diphosphate
E) None of the above.
6. How many protons (p), electrons (e), and neutrons (n) are there in
A) 27 p, 13e, and 27 n
B) 13 p, 10e, and 14 n
C) 13p, 14e, and 13 n
D) 13p, 13e, and 14n
E) None of the above.
27
13
Al 3+ ?
2
7. A hypothetical element has two stable isotopes. One isotope has an abundance of
64.800% with a mass of 46.046 amu. Determine the value in amu of the second isotope if
the average mass of the element is 47.740 amu?
A) 46.046 amu
B) 50.83 amu
C) 50.859 amu
D) 47.740 amu
E) None of the above.
8. How many grams of carbon are present in 30.5 g of Na2CO3?
A) 5.08 g
B) 30.5 g
C) 12.0 g
D) 3.46 g
E) None of the above.
9. How many moles of sulfur are in 2.40 mol of V2(SO4)3?
A) 2.40 mol
B) 4.80 mol
C) 7.20 mol
D) 9.60 mol
E) None of the above.
10. For the reaction shown, calculate the mass of NO2 formed when 1.30 mol of N2O5
completely react.
2 N2O5(g) → 4 NO2(g) + O2(g)
A) 59.8 g
B) 1.20 x 102 g
C) 0.60 g
D) 239 g
E) None of the above.
11. What mass of HCl is present in 0.250 L of a solution with a pH of 2.85?
A) 1.28 × 10-2 g
B) 5.13 × 10-2 g
C) 1.4 × 10-3 g
D) 1.3 × 10-2 g
E) None of the above.
12. Which of the following solutions would form a precipitate when added to a solution
of copper(II) sulfate? Choices: Solutions of lithium hydroxide, silver nitrate, and calcium
chloride, respectively.
A) Lithium hydroxide is the only solution which would form a precitpitate.
B) Silver nitrate is the only solution which would form a precitpitate.
C) Calcium chloride is the only solution which would form a precitpitate.
D) Any of these solutions would form a precipitate.
E) None of the above.
3
13. Which of the following represents a redox reaction (these may not be balanced)?
A) Sr(OH)2(aq) → Sr2+(aq) + 2 OH-(aq)
B) K2CO3(aq) + NiCl2(aq) → NiCO3(s) + KCl(aq)
C) ClO-(aq) + Cr(OH)4-(aq) → CrO42-(aq) + Cl-(aq)
D) HCl(aq) + Ba(OH)2(aq) → H2O(l) + BaCl2(aq)
E) None of the above.
14. How many moles of calcium hydroxide are needed to neutralize 250.0 mL of
hydrochloric acid solution with a pH of 6.00?
A) 2.5 × 10-7 mol
B) 2.50 × 10-6 mol
C) 1.3 × 10-7 mol
D) 3.21 × 10-4 mol
E) None of the above.
15. If a small amount of glucose (sugar) is put into water, which of the following is true?
A) It remains a solid.
B) The concentration of the cation is greater than that of the anion.
C) The concentration of the cation is less than that of the anion.
D) The concentration of the cation is equal to that of the anion.
E) None of the above.
16. A solution containing 10 g of Pb(NO3)2(aq) is mixed with a solution containing 5.0 g
of KI(aq). Which of the following is true?
M(Pb(NO3)2) = 331.21 g/mol and M(KI) = 169.00 g/mol
A) The limiting reagent is Pb(NO3)2(aq).
B) The limiting reagent is KI.
C) No reaction occurs.
D) There is no excess reactant.
E) None of the above.
17. If a basic solution is diluted by a factor of 100, which of the following is true?
A) The pH decreases.
B) The pOH remains constant.
C) The pH increases.
D) The pOH decreases.
E) None of the above.
18. Given is the following unbalanced reaction.
C8H18(g) + O2(g) → CO2(g) + H2O(g)
How many moles of carbon dioxide and water are produced from the complete
combustion of 1 mol of this hydrocarbon?
A) 8 mol of carbon dioxide and 9 mol of water.
B) 16 mol of carbon dioxide and 18 mol of water.
C) 1 mol of carbon dioxide and 1 mol of water.
D) 4 mol of carbon dioxide and 9 mol of water.
E) None of the above.
4
19. What is the balanced equation for the gas-evolving reaction between HNO3(aq) and
Na2SO3(aq) ?
A) 2 HNO3(aq) + Na2SO3(aq) → H2O(l) + SO2(g) + NaNO3(aq)
B) HNO3(aq) + Na2SO3(aq) → H2O(l) + SO2(g) + NaNO3(aq)
C) 2 HNO3(aq) + Na2SO3(aq) → H2O(l) + SO2(g) + 2 NaNO3(aq)
D) HNO3(aq) + 2 Na2SO3(aq) → 2 H2O(l) + 2 SO2(g) + NaNO3(aq)
E) None of the above.
20. A 0.465 g sample of an unknown gaseous compound occupies 245 mL at 298 K and
1.22 atm. What is the molar mass of the unknown compound?
A) 26.3 g/mol
B) 38.0 g/mol
C) 12.2 g/mol
D) 26.3 g/mol
E) 81.8 g/mol
21. Determine the volume of O2 (at STP) formed when 50.0 g of KClO3 decomposes
according to the following reaction.
2 KClO3(s) → 2 KCl(s) + 3 O2(g)
A) 9.14 L
B) 8.22 L
C) 12.3 L
D) 13.7 L
E) 14.6 L
22. A gas mixture contains CO, Ar and H2. What is the total pressure of the mixture, if
the mole fraction of H2 is 0.35 and the partial pressure of H2 is 0.58 atm?
A) 0.20 atm
B) 1.7 atm
C) 0.49 atm
D) 2.1 atm
E) 0.60 atm
23. The atomic mass unit is based on
A) a particular isotope of hydrogen
B) the average mass of helium
C) the natural abundance of carbon
D) None of the above statements is correct
E) All of the above statements are correct.
24. Calculate the density in g/L of CO2 gas at 27 ºC and 0.50 atm pressure.
A) 1.1 g/L
B) 9.9 g/L
C) 0.89 g/L
D) 46 g/L
E) 4.6 g/L
5
25. Determine the theoretical yield and the percent yield if 21.8 g of K2CO3 is produced
from reacting 27.9 g KO2 with 29.0 L of CO2 (at STP).
M(KO2) = 71.10 g/mol and M(K2CO3) = 138.21 g mol-1
4 KO2(s) + 2 CO2(g)
→ 2 K2CO3(s) + 3 O2(g)
A) 27.1 g; 80.4%
B) 179 g; 12.2%
C) 91.7 g; 23.8%
D) 206 g; 10.6%
E) 61.0 g; 35.7%
26. Balance the following REDOX equation which occurs in basic solution.
Cl2O7(g) + H2O2(aq) →
ClO2(aq) + O2(g)
Which one of the following statements is correct? (Note: If more than one statement is
correct, pick only E) as your answer.)
A) The oxidation number of the chlorine atom in ClO2 is +3.
B) Cl2O7(g) is the oxidizing agent.
C) 3 moles of H2O2(aq) are oxidized for every 3 moles of O2(g) produced.
D) The oxidation number of the chlorine atom increases in the reaction.
E) More than one statement is correct.
27. According to the Bronsted-Lowry theory, acid-base reactions can be rationalized with
the help of conjugated acid-base pairs. Which of the following statements is correct,
when ammonia dissolves in water? (Note: If more than one statement is correct, pick only
E) as your answer.)
A) NH3 and H2O are a conjugated acid-base pair.
B) NH3 and NH4+ are a conjugated acid-base pair.
C) NH3 and H3O+ are a conjugated acid-base pair.
D) H2O and OH– are a conjugated acid-base pair.
E) More than one statement is correct.
28. Which of the following statements is correct with respect to an ideal gas? (Note: If
more than one statement is correct, pick either D) or E) as your answer.)
A) For an ideal gas, there are no forces of interaction between the individual gas
particles.
B) For an ideal gas, the volume(s) of the gas particles are considered to be zero.
C) For an ideal gas, the pressure is always assumed to be 1.00 atm.
D) Both A) and B) are true
E) Both A) and C) are true
29. 0.1 mol of NaCl(s) is added to 1.0 L of water. This is an example of preparing a(n)
A) element
B) compound
C) pure substance
D) homogeneous mixture
E) heterogeneous mixture
6
30. A gas at a pressure of 740 Torr at 20 ºC and volume of 1.00 L has a mass of 1.134 g.
If the empirical formula of the compound is CH2 what is its molecular formula?
A) CH2
B) C2H4
C) C3H6
D) C4H8
E) C6H6
31. A mixture of gases contains 0.30 mol of A, 0.40 mol of B and 1.3 mol of C. The mole
fraction of compound B in the mixture is:
A) 0.67
B) 0.40
C) 0.20
D) 0.12
E) None of the above.
32. A student is preparing a sample of NaCl. She determines the mass of her watchglass
plus sample to be 6.3455 g. The mass of the watchglass after sample transfer is 5.8855 g.
To the correct number of significant figures, how many moles of NaCl have been
transferred?
A) 7.87 x 10-3 mol NaCl
B) 7.871 x 10-3 mol NaCl
C) 7.8715 x 10-3 mol NaCl
D) 7.87153 x 10-3 mol NaCl
E) None of the above.
33. A mixture of N2 and Cl2 has partial pressures 0.300 atm and 0.700 atm respectively at
25 ºC. A volume of 1.05 L contains how many grams of nitrogen?
A) 1.20 g
B) 0.361 g
C) 0.841 g
D) 2.92 g
E) None of the above.
34. Which of the following solutions has a pH of 3.00?
A) 0.010M HClO4
B) 10-3M HF + 0.100M KCl
C) 0.0010 M CH3COOH
D) 0.0010 M HBr
E) 10-3 M KOH
35. What volume of 0.200M NaOH is needed to titrate 40.00 mL of 0.150M nitric acid to
the equivalence point?
A) 30.0 mL
B) 0.857 mL
C) 46.7 mL
D) 60.0 mL
E) 23.4 mL
7
36. Which one of the following salt solutions will NOT form a precipitate when it is
mixed with CaCl2(aq)?
A) Na2S (aq)
B) AgNO3 (aq)
C) PbSO4 (aq)
D) (NH4)2CO3 (aq)
E) Both A) and D)
37. For the reaction shown below, how many grams of Al2O3 can be formed from the
reaction of 1.00 x 102 g of Al and 2.00 mol of O2?
4Al(s) + 3O 2 (g) → 2Al2 O3
A) 1.89 x 102g
B) 1.85 g
C) 96.1 g
D) 1.33 g
E) 1.36 x 102 g
38. Balance the following REDOX reaction occurring in acidic conditions. What are the
numeric values of the stochiometric coefficients a,b,c,d ?
a SO32- (aq) + b MnO4- (aq) → c SO42- (aq) + d Mn2+ (aq)
A)
B)
C)
D)
E)
a = 1 ; b = 4; c = 4; d = 2
a = 5 ; b = 2; c = 5; d = 2
a = 2 ; b = 5; c = 1; d = 4
a = 3 ; b = 1; c = 1; d = 3
a = 4 ; b = 2; c = 3; d = 1
39. What is the oxidation state of chlorine in Ca(ClO3)2?
A) +7
B) +5
C) +3
D) +1
E) -1
40. If 25.00 mL of H2O (density 1.00 g/mL) is diluted with ethanol to a final volume of
250.0 mL, what is the concentration of water in the final solution?
A) 5.55 M
B) 6.17 M
C) 55.5 M
D) 0.180 M
E) 0.162 M
41. To what volume should you dilute 10.00 mL of a 1.50 M solution to obtain a 0.300 M
solution?
A) 5.00 mL
B) 10.0 mL
C) 25.0 mL
D) 50.0 mL
E) 100.0 mL
8
42. In the following reaction which species is acting as a reducing agent?
Al (s) + NO3- (aq) + 4 H+ (aq) → Al3+ (aq) + NO (g) + 2 H2O (l)
A) NO (g)
B) Al3+ (aq)
C) H+ (aq)
D) NO3- (aq)
E) Al (s)
43. The number of molecules in 1.55 g of CO2 is:
A) 1.55 x 1022
B) 1.95 x 1022
C) 2.12 x 1022
D) 2.82 x 1022
E) None of the above.
44. A sample of unknown compound weighing 0.155 g contains 5.19 x 1021 molecules.
The molar mass of this compound is:
A) 15.5 g mol-1
B) 18.0 g mol-1
C) 21.1 g mol-1
D) 23.4 g mol-1
E) None of the above.
45. How many molecules of ethanol (C2H5OH) are present in a 1-mL sample of ethanol
(density = 0.789 g/mL).
A) 1.03 x 1022
B) 1.48 x 1022
C) 1.99 x 1022
D) 2.03 x 1022
E) 2.13 x 1022
46. 1.5 mol of H2SO4 contain
A) 9.0 x 1023 H2SO4 molecules.
B) 48 g S.
C) 1.8 x 2024 H atoms.
D) All of the above answers are correct.
E) None of the above answers is correct.
47 Which of the following compounds has the highest mass percentage of carbon?
A) H2CO3
B) C2H4O2
C) CO2
D) CaCO3
E) CO
9
48. Decomposition of a compound consisting of Be, S and O yielded 2.128 g of Be, 7.557
g of S and 15.107 g of O. Calculate the empirical formula for this compound.
A) BeSO3
B) BeSO4
C) BeS2O3
D) BeS4O6
E) BeS6O6
49. Calculate the molecular formula for nicotine (molar mass 162 g mol-1) based on the
following mass percent composition: % C = 74.03, % H = 8.70, % N = 17.27.
A) C8H12N
B) C8H14N
C) C10H12N2
D) C10H14N2
E) C12H14N2
50. Which match of the name and formula is not correct?
A) Potassium sulfide - K2S
B) Iron(III) oxide - Fe2O3
C) Phosphorus pentachloride - PCl5
D) Sodium hypochlorite - NaClO2
E) Both B) and D).
10
1
18
Periodic Table of the Elements
1
H
2
He
1.00794
2
13
14
15
16
17
4.00260
3
4
5
6
7
8
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
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
Physical Constants
Constant
Atomic mass unit
Avogadro number
Gas Constant
(244)
(243)
Symbol
u
NA
R
(247)
(251)
(252)
(257)
(258)
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
2.9979 × 108 m s-1
2.179 × 10-18 J
9.109 × 10-31 Kg
Molar volume of an ideal gas at STP
Planck constant
Speed of light in a vacuum
Rydberg Constant
Electron mass
Vm
h
c
RH
me
Some SI Derived Units
Physical Quantity
Force
Energy
Pressure
Symbol
N
J
Pa
Unit
Newton
Joule
Pascal
(247)
Definition
kg m s-2
kg m2 s-2
N m-2 = kg m-1 s-2
STP Conditions: P = 1 atm = 760 Torr = 760 mmHg = 101.325 kPa
Temperature = 0 ºC = 273.2 K
11
(259)
(260)