CHEM 107 (Fall-2006)
Final Exam (100 + 4 pts)
Name: ------------------------------------------------------------------------, Clid # -----------------------------LAST NAME, First
(Circle the alphabet segment of your LAST NAME): A, B
C-G
H-N
O-S
T-Z
Please answer the following questions:
Part I: Multiple Choices (44 pts: 22 @ 2 pts each + 4 pts bonus). Circle the ONE best answer:
1. Which of the following species have bent (angular) molecular shape?
I) CO2
III) NO2+
II) OF2
a) only II
b) only IV
c) II and IV
d) I and III
IV) NO2-
2. Which of the following ions is expected to be paramagnetic?
a) Zn2+
b) S2-
c) Cu+
d) Ti3+
3. The ground state electron configuration of tantalum, Ta (Z = 73) is
a) [Xe] 5d3 6s2
b) [Xe] 4f14 5d3 6s2
c) [Xe] 4f14 6d3 6s2
d) [Xe] 4f14 5d5
4. The oxidation numbers of phosphorus, P in PCl3 and P2O74- are:
a) -3 and +10, respectively
b) -3 and +7, respectively
c) -3 and +5, respectively
d) +3 and +5, respectively
5. If a gold ring has a mass of 5.50 g in temperature from 25.0 to 28.0 ºC, how much heat is
absorbed? (specific heat of gold is 0.129 J/g ºC)
a) 2.1 J
b) -2.1 J
c) 0.24 J
d) 130 J
6 Which of the following statements is false?
a) An electron transition from n = 1 to n = 3 absorbs energy.
b) Light emitted by an n = 5 to n = 2 transition will have a shorter wavelength than that from
n = 4 to n = 2 transition.
c) An atom of group 16 has two unpaired electrons.
d) All of the above.
7. Which of the following molecules is expected to be polar?
a) BeF2
b) SF6
c) XeF4
d) OF2
1
8. Calculate ∆H° for the following reaction using the given enthalpies of formation.
2 NO (g) + 5 O2 (g)
2 NO2 (g)
∆Hf° NO (g) = 90.25 kJ/mol & ∆Hf° NO2 (g) = 33.18 kJ/mol
b) +57.07 kJ
b) -57.02 kJ
c) -114.14
d) +114.14 kJ
9. Which of the following is most likely to involve sp3d hybrid orbitals at the central atoms?
I) ClF3
II) BrF5
III) XeF4
a) I and IV
b) only II
c) only IV
d) II and III
IV) SF4
10. Which of the following has the greatest ionization energy?
a) Br
b) Sn
c) Se
d) Cl
11. Which name is incorrect?
a) Ca3P2: calcium phosphide
b) Na2S: sodium sulfide
c) P2S5: diphosphorus pentasulfide
d) Co2O3: cobalt(III) trioxide
12. Aluminum and oxygen react according to the following equation:
4 Al (s) + 3 O2 (g)
2 Al2O3 (s)
What mass of Al2O3 (102.0 g/mol), in grams, can be made by reacting 2.3 g of Al with excess
oxygen?
a) 8.7 g
b) 17.4 g
c) 4.3 g
d) no answer was give
13. If 400.0 mL of 0.375 M NaOH is added to 280.0 mL of 0.600 M HNO3, will the mixture be
a) neutral
b) basic
c) acidic
d) amphoteric
14. Calcium metal and bromine react to form calcium bromide, CaBr2. Which statement is correct?
a) Ca atom loses two electrons and becomes Ar atom.
b) Br atom gains an electron and become Kr atom.
c) The Ca and Br atoms change into different, more stable atoms.
d) CaBr2 is predominantly an ionic compound.
15. The standard enthalpy change for the following reaction is -53.0 kJ.
2 HI (g)
H2 (g) + I2 (s)
What is the standard enthalpy of formation of HI (g)?
a) 53.0 kJ
b) -105.9 kJ
c) 26.5 kJ
d) -53.0 kJ
2
16. An atom containing 26 protons and a mass number of 59, would be:
a) Fe
b) Co
c) As
d) Ni
17. The element X occurs naturally to the extent of 20.0% 12X and 80.0% 13X. the atomic mass of X
is nearest
18.
a) 12.8
b) 12.2
c) 12.5
d) 13.0
Equal volumes of an unknown gas and nitrogen (N2) gas takes 5.37 min and 3.55 minutes,
respectively to effuse through a small hole. Calculate the molar mass of the gas.
a) 64.1
b) 12.2
c) 42.4
d) 128
19. The greatest deviation from the Ideal Gas Law is expected at:
a) high T, high P
b) low T, high P
c) high T, low P
d) low T, low P
20. A 4.8 g sample of a compound of nitrogen and oxygen contains 3.02 g of oxygen. What is the
simplest formula?
a) NO2
b) N2O3
c) N2O
d) NO
21. Which of the following ions has the largest ionic radius?
a) Se2-
b) Cs+
c) S2-
d) Sr2+
22. In the phase diagram shown here. Which statement applies?
a) The path A
Phase Diagram of Substance Z
C represents sublimation.
b) Following the path A
B
C, the
compound would first liquefy and then vaporize.
c) If the compound is in state A, continued reduction
of the pressure (at constant T) will cause it to melt.
d) None of these statements is correct.
23. Consider the above phase diagram, what is the normal melting point of the pure substance Z?
a) +18 ºC
b) -22 ºC
c) - 2 ºC
d) +4 ºC
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24. Using the same diagram, if the average atmospheric pressure at the top of certain mount, which is
about 19,000 feet above the sea level is 0.526 atm, What is the approximate boiling temperature
of the liquid?
a) 20 ºC
b) 140 ºC
c) 5 ºC
d) can not be determined from this graph
Part II. Bonding and Chemical Equations (26 pts):
A) Bonding & molecular structure (12 pts):
1. Draw the Lewis structure for the SO2 molecule, draw the resonance structures, if there is any then
predict:
a) the molecular shape
b) hybridization of the central atom
c) number σ and π bonds
d) bond angle
Lewis Structure & resonance structures (if any)
a) Molecular shape: -----------------------b) Hybridization of the central atom: ------c) # of σ bonds ------and # of π bonds -------d) Bond angle: -----------------
B) Chemical Equations (16 pts):
2. (8 pts) Balance the following redox equation in acidic solution:
UO22+ (aq) + Te (s)
U4+ (aq) + TeO42- (aq),
Then identify the oxidizing agent and how many electron(s) are transferred per one mole of the
oxidizing agent.
Balanced equation:
Oxidizing agent: -------------Number of electrons/mole of oxidizing agent: -------4
2. (6 pts) Write the balanced chemical equation and the net ionic equation for the reaction between
aqueous solutions of HNO3 (aq) and CaCO3 (s) and then identify the spectator ion(s)
Chemical equation:
Net ionic equation:
Spectator ion(s):
Part III. Calculations (30 pts: 5 @ 6 pts each) Show all work for full credit. Please express all
answers with the proper units and correct number of significant figures.
1. Given the following equations:
2 H2 (g) + O2 (g)
2 H2O (l)
∆Hrxn° = -571.6 kJ
N2 (g) + O2 (g)
2 NO (g)
∆Hrxn° = +180.5 kJ
N2 (g) + 3 H2 (g)
2 NH3 (g)
∆Hrxn° = -92.2 kJ
Determine the enthalpy change, ∆Hrxn° for the following reaction:
2 NO (g) + 5 H2 (g)
2 NH3 (g) + 2 H2O (l)
∆Hrxn° = ??
∆Hrxn° = -844.3 kJ
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2. If a 17.0 g of impure nickel metal reacts with excess carbon monoxide, CO forming 6.25 L of
Ni(CO)4 gas (MM = 170.75 g/mol) under standard temperature and pressure conditions. What is
the percent by mass of nickel in the impure nickel metal sample?
Ni(s) + 4 CO (aq)
Ni(CO)4 (g)
b) 96.3% Ni
3. Oxyacetylene torches used for welding reach temperatures near 2000 °C. The reaction involved in the
combustion of acetylene is
2 C2H2 (g) + 5 O2 (g)
4 CO2 (g) + 2 H2O (g)
Starting with 175 g of both acetylene, C2H2 and oxygen:
a) What is the limiting reactant?
b) If 68.5 L of carbon dioxide (d = 1.85 g/L) is produced, what is the percent yield of the reaction at
the same conditions of temperature and pressure?
a) Limiting reactant:
b) % yield =
6
4. The reaction of a copper penny with nitric acid results in the formation of a red-brown gaseous
compound containing nitrogen and oxygen. A sample of the gas at a pressure of 727 mmHg and a
temperature of 18 ºC weighs 0.289 g in a flask with a volume of 157.0 mL. Calculate the molar mass
of the gas, and suggest a reasonable chemical formula for the compound (NO, NO2, N2O, N2O5,
N2O4).
M = 45.9 g/mol, NO2
5. Vitamin C, the compound that believes to prevent the common cold, has the composition 40.92% C,
4.58% H and 54.50% O. Determine the simplest formula of the compound. In another experiment,
the molar mass of the vitamin was found to be about 180 g/mol. What is the molecular formula of
vitamin C?
Simplest Formula
Molecular Formula
C3H4O3
(C3H4O3)2
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PREFERENCE SHEET FOR
CHEM 107
Final Exam – Fall 2006
You will have 140 minutes to complete this exam. The exam has 7 pages plus the Periodic Table and
Reference page.
When you are told to do so, tear off the Periodic Table cover sheet and use as required during the exam.
Equations and Constants:
Density (d) = mass/volume
q = m x c x ∆T
PV = nRT
K.E. = ½ mv2
Average speed of a gas, u = (3RT/M)1/2
(Rate of effusion of B/Rate of effusion of A) = (MA/MB)1/2
ν = RH/h [1/(nlo)2 – 1/(nhi)2]
E=hν
c=λν
RH = 2.180 x 10-18 J
h = 6.626 x 10-34 J.s
c = 3.00 x 108 m/s
Avogadro’s Number = 6.022 x 1023
R = 0.0821 L.atm/mol.K
1 atm = 760 torr = 760 mmHg
At STP 1 mol of a gas = 22.414 L
At STP: T = 273 K, P = 1 atm
General Solubility Guidelines
All nitrates are soluble.
All salts of sodium, potassium and ammonium are soluble.
All chlorides, bromides and iodides are soluble except Ag+, Hg22+, and Pb2+.
All sulfates are soluble except Ba2+, Sr2+, Pb2+ and Hg22+.
All acetates, chlorates and perchlorates are soluble.
Everything else will be considered insoluble.
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1
1
2
H
Periodic Table of the Elements
He
1.01
3
2
3
4
5
4.00
4
5
6
7
8
9
10
Li Be
B
C
N
O
F
Ne
6.94
9.01
10.81 12.01 14.01 16.00 19.00 20.18
11
12
13
14
15
16
17
Na Mg
Al Si
P
S
Cl Ar
22.99 24.30
26.98 28.08 30.97 32.06 35.45 39.95
19
20
K
Ca Sc Ti V
39.1
40.08 44.96 47.88 50.94 52.00 54.94 55.85 58.93 58.69 63.55 65.38 69.72 72.59 74.92 78.96 79.90 83.80
37
38
21
39
Rb Sr Y
22
40
23
41
24
25
55
56
57
26
27
28
29
30
31
32
33
34
35
42
43
44
45
46
47
48
49
50
51
52
53
Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I
72
73
36
Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
85.47 87.62 88.91 91.22 92.91 95.94 (98)
6
18
74
75
54
Xe
101.1 102.9 106.4 107.9 112.4 114.8 118.7 121.8 127.6 126.9 131.1
76
77
Cs Ba La Hf Ta W Re Os Ir
78
79
80
81
82
83
84
85
86
Pt Au Hg Tl Pb Bi Po At Rn
132.9 137.3 138.9 178.5 181.0 183.8 186.2 190.2 192.2 195.1 197.0 200.6 204.4 207.2 209.0 (209) (210) (222)
87
7
88
89
104 105 106 107 108 109 110 111 112
Fr Ra Ac Rf Db Sg Bh Hs Mt Uun Uuu Uub
(223) 226.0 227.0 (261) (262) (263) (262) (265) (266) (269) (272) (277)
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
140.1 140.9 144.2 (145) 150.4 152.0 157.2 158.9 162.5 164.9 167.3 168.9 173.0 175.0
90
91
92
Th Pa U
93
94
95
96
97
98
99
100 101 102 103
Np Pu Am Cm Bk Cf Es Fm Md No Lr
232.0 231.0 238.0 237.0 (244) (243) (247) (247) (251) (252) (257) (258) (259) (260)
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