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University of Saskatchewan
Department of Chemistry
CHEMISTRY 112.
Midterm Examination (Sat. Oct 28th, 2006, 10:00 AM – 12:00 noon)
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Student Number Signature ___________________________________
Please indicate your section:
Section 01 MWF 8:30 am Dr. C. Paige Section 03 MWF 9:30 am Dr. K. Brown Section 05 MWF 10:30 am Dr. M. Paige Section 07 MWF 11:30 am Dr. P. Ahiahonu Section 09 T/Th 10:00 am Dr. J. Müller Section 91 MWF 8:30 am Dr. L. Wilson Section 97 St. Peter's College Dr. A. Szmigielski Section C11 Cumberland Regional College Dr. A. Szmigielski Section C15 Woodland Institute - Prince Albert Dr. R. Zee Section C51 North West Regional College - North Battleford
Dr. R. Zee
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 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) If you have not already done so, please fill out the top of this paper now and on the blue sheet, print your name (legibly!) and code your student number on the computer blue sheet in soft pencil. e) When handing in your exam, place the blue computer sheet on top of this paper and hand-in BOTH together. Check that your answers match on blue sheet and exam paper before handing it in. f) 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. g) You can use the back sides of the following 10 pages as scratch paper.
1. A rectangular metallic sheet has a surface area of 2.452 cm^2 and a mass of 2.88 g. What is the thickness of the metallic sheet in centimeter if its density is 20.98 g cm -3^? A) 17.86 cm B) 5.60 x 10 -2^ cm C) 5.598 cm D) 0.3366 cm E) 2.971 cm 2. Determine the number of protons (p), electrons (e) and neutrons (n) in 2713 Al 3+.
A) 27(p), 27(e), and 13 (n) B) 13(p), 13(e), and 14(n) C) 13(p), 13(e), and 14(n) D) 13(p), 10(e), and 14(n)
3. How many grams of calcium are present in 20.0 g of CaCO 3? A) 8.01 g Ca B) 4.00 g Ca C) 4.08 g Ca D) 2.08 g Ca E) 40.08 g Ca 4. 50.00 g of NaCl are dissolved in water to give a solution that contains 2.500 % NaCl by mass. The density of the solution is 1.030 g/mL. The volume of the solution is A) 941.8 mL B) 1.942 L C) 2.500 L D) 50.0 mL 5. 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 6. The fictional element yarrow (Yr) consists of two isotopes. The fictional isotope 60 Yr has an atomic mass of 60.15 u while 70 Yr has an atomic mass of 70.16 u. The average atomic mass of Yr is 69.41 u. The natural abundance of 60 Yr is A) 7.493% B) 3.759% C) 9.437% D) 8.566% 7. A sample of an unknown element weighing 22.6 g contains 3.40 x 10^24 atoms. The molar mass of this element is: A) 1.00 g mol - B) 4.00 g mol - C) 6.94 g mol - D) 9.01 g mol -
15. The molecular formula for adipic acid is C 6 H 10 O 4. The percent mass of O in this sample is A) 20 % B) 48 % C) 44 % D) 7 % 16. The oxidation state (number) of the manganese atom in KMnO 4 ·6H 2 O is A) + B) + C) + D) + 17. What is the molarity of a 2.00 mL acetic acid solution if 17.24 mL of 0.1089 M sodium hydroxide are needed to titrate it to an equivalence point? A) 0.939 M B) 0.126 M C) 0.469 M D) sodium hydroxide cannot be standardized because it is hygroscopic (absorbs water) E) none of the above 18. What happens when a solution of iron(III) nitrate is mixed with a solution of sodium hydroxide? A) Nothing (no reaction) B) This is an acid-base reaction. An indicator is required to view the reaction. C) Iron(III) is reduced to iron(II) D) A precipitate of sodium nitrate forms E) A precipitate of iron(III) hydroxide forms 19. Balance the following REDOX equation which occurs in basic solution.
Cl 2 O 7 (g) + H 2 O 2 (aq) o ClO 2 (aq) + O 2 (g)
Which one of the following statements is correct? A) The oxidation number of the chlorine atom in ClO 2 is +3. B) Cl 2 O 7 (g) is the oxidizing agent. C) 3 moles of H 2 O 2 (aq) are reduced for every 3 moles of O 2 (g) produced. D) The oxidation number of the chlorine atom increases in the reaction. E) More than one statement is correct.
20. Uranium (U) can react with fluorine gas (F 2 ) according to the following equation.
U(s) + 3 F 2 (g) o UF 6 (s)
In a particular experiment 2.0 mol of U(s) is allowed to react with 3.0 mol of F 2 (g). Which one of the following statements about this experiment is correct? A) U(s) is the limiting reagent. B) F 2 (g) is the limiting reagent. C) 2.0 mol of UF 6 (s) should be produced. D) 3.0 mol of UF 6 (s) should be produced. E) none of the above.
21. The simultaneous oxidation and reduction of a single chemical species is an example of A) a complexation reaction B) a precipitation reaction C) an acid base reaction D) a disproportionation reaction 22. The mass percent of calcium in milk is 0.118 %. How many calcium atoms are present in 250.0 g of milk? A) 3.76 u 1024 B) 4.43 u 1023 C) 4.43 u 1021 D) 7.36 u 10 - E) 7.36 u 105 23. When aqueous solutions of sodium sulphate and lead(II) nitrate are mixed, lead sulphate precipitates. The mass of lead sulphate formed when 1.25 L of 0.0500 M lead(II) nitrate and 2.00 L of 0.0250 M sodium sulphate are mixed is A) 19.0 g B) 15.2 g C) 38.0 g D) 30.4 g E) 3.25 g 24. 0.1 mol 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 25. How many moles of ions – both cations and anions – are present in solution when 0.75 mol of potassium chloride is dissolved in 0.25 L of distilled water? A) 0.75 mol B) 0.8 mol C) 1.5 mol D) 2.0 mol 26. Aqueous solutions of aluminum nitrate and sodium hydroxide are mixed to give a white precipitate of aluminum hydroxide and a solution of sodium nitrate. Which of the following equations represents a balanced chemical equation for this reaction?
A) Al(NO 3 ) 2 (aq) + NaOH(aq) o 2 NaNO 3 (aq) + Al(OH) 2 (s)
B) Al(NO 3 ) 2 (aq) + 2 NaOH(aq) o 2 NaNO 3 (aq) + Al(OH) 2 (s)
C) Al(NO 2 ) 3 (aq) + 2 NaOH(aq) o 2 NaNO 2 (aq) + Al(OH) 3 (s)
D) Al(NO 3 ) 3 (aq) + 3 NaOH(aq) o 3 NaNO 3 (aq) + Al(OH) 3 (s)
E) 3 Al(NO 3 ) 3 (aq) + NaOH(aq) o NaNO 3 (aq) + 3 Al(OH) 3 (s)
33. For radiation of wavelength 500.0 nm the energy of one mole of photons is A) 239.3 kJ / mol B) 500.0 J / mol C) 1043.5 kJ / mol D) 39.3 J / mol 34. Which of the following reactions yield a solid precipitate?
A) AgNO 3 (aq) + NaBr(aq) ĺ
B) HCl(aq) + NH 3 (aq) ĺ
C) Cu 2+(aq) + 4 NH 3 (aq) ĺ
D) NaNO 3 (aq) + NaBr(aq) ĺ
35. Einstein was able to explain the photoelectric effect by assuming that A) all different electrode materials emit electrons above the same frequency of light. B) light is an electromagnetic wave. C) light has particle-like properties. D) None of the above statements is correct. 36. The deBroglie wavelength of a beam of electrons was determined to be 400 nm. That means that electrons travel with a speed of A) 6.78 x 10^3 m/s B) 3.00 x 10^6 m/s C) 1.82 x 10^3 m/s D) 8.00 x 10^8 m/s 37. The density of water is 1.00 g/mL at 4o^ C. How many water molecules are present in 2.56 mL of water at this temperature? A) 4.00 x 10^22 B) 6.02 x 10^23 C) 8.56 x 10^22 D) None of the above values is correct. 38. Titanium dioxide, the substance used as the pigment in white paint, is prepared industrially by reaction of TiCl 4 with O 2 at high temperature. TiCl 4 (g) + O 2 (g) ĺ TiO 2 (s) + 2 Cl 2 (g) How many kilograms of TiO 2 can be prepared from 5.00 kg of TiCl 4? A) 2.11 kg B) 3.67 kg C) 4.90 kg D) 5.22 kg
39. Consider the following energy levels of a hypothetical atom: E 4 = -1.00 x 10-19^ J E 3 = -5.00 x 10-19^ J E 2 = -10.0 x 10-19^ J E 1 = -15.0 x 10-19^ J What is the wavelength of the photon needed to excite an electron from E 1 to E 4? A) 400 nm B) 643 nm C) 142 nm D) None of the above values is correct. 40. Use your knowledge of atomic electron configurations to predict which one of the following atoms in the gas phase would have three unpaired electrons. A) Be B) Al C) Cl D) P 41. Hund’s rule states that A) no two electrons can have the same four quantum numbers. B) a set of degenerate orbitals are first singly filled with electrons having parallel spins. C) all second period elements must fulfill Hund’s octet. D) None of the above statements is correct. 42. The multiplication of 1 cm with 1 Gm (G = giga) results in A) 10^6 m^2 B) 10^4 m^2 C) 10^7 m^2 D) 10-3^ m^2 43. The oxidation state (number) of Ca in CaH 2 is A) 0 B) + C) + D) - 44. Which of the following samples contains the largest number of atoms? A) 1 g of Li B) 1 g of C C) 1 g of O 2 D) All contain the same number of atoms. 45. What is the value for the missing quantum number l in the following set? n = 3, l = ?, m l = -2, ms = +½ A) 1 B) 2 C) 3 D) 4
1 Periodic Table of the Elements 18
1
H
2
He
3
Li
4
Be
5
B
6
C
7
N
8
O
9
F
10
Ne
11
Na
12
Mg
13
Al
14
Si
15
P
16
S
17
Cl
18
Ar
19
K
20
Ca
21
Sc
22
Ti
23
V
24
Cr
25
Mn
26
Fe
27
Co
28
Ni
29
Cu
30
Zn
31
Ga
32
Ge
33
As
34
Se
35
Br
36
Kr
37
Rb
38
Sr
39
Y
40
Zr
41
Nb
42
Mo
43
Tc
(98)
44
Ru
45
Rh
46
Pd
47
Ag
48
Cd
49
In
50
Sn
51
Sb
52
Te
53
I
54
Xe
55
Cs
56
Ba
57
La
72
Hf
73
Ta
74
W
75
Re
76
Os
77
Ir
78
Pt
79
Au
80
Hg
81
Tl
82
Pb
83
Bi
84
Po
(209)
85
At
(210)
86
Rn
(222) 87
Fr
(223)
88
Ra
89
Ac
104
Rf
(261)
105
Db
(262)
106
Sg
(263)
107
Bh
(262)
108
Hs
(265)
109
Mt
(266)
110
(269)
111
(272)
112
(272)
114
(287)
116
(289)
118
(293) 58
Ce
59
Pr
60
Nd
61
Pm
(145)
62
Sm
63
Eu
64
Gd
65
Tb
66
Dy
67
Ho
68
Er
69
Tm
70
Yb
71
Lu
90
Th
91
Pa
92
U
93
Np
94
Pu
(244)
95
Am
(243)
96
Cm
(247)
97
Bk
(247)
98
Cf
(251)
99
Es
(252)
100
Fm
(257)
101
Md
(258)
102
No
(259)
103
Lr
(260)
Physical Constants Constant Symbol Value Atomic mass unit u 1.6605 × 10-27^ kg Avogadro number NA 6.0221 × 10^23 mol - Gas Constant R 0.082058 L atm mol -1^ K- 8.3145 J K-1^ mol - 62.364 L mmHg mol-1^ K- Molar volume of an ideal gas at STP Vm 22.414 L mol - Planck constant h 6.6261 × 10-34^ J s Speed of light in a vacuum c 2.9979 × 10^8 m s - Rydberg Constant RH 2.179 × 10-18^ J Electron mass (^) me 9.109 × 10-31^ Kg
Some SI Derived Units Physical Quantity Unit Symbol Definition Force Newton N kg m s - Energy Joule J kg m^2 s - Pressure Pascal Pa N m-2^ = kg m-1^ s -
STP Conditions: P = 1 atm = 760 Torr = 760 mmHg = 101.325 kPa
Temperature = 0 ºC = 273.2 K
