CHEM 107 (Fall

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CHEM 107 (Spring-2004)
Final Exam (100 pts)
Name: ------------------------------------------------------------------------, SSN -------------------------------LAST NAME, First
(Circle the alphabet segment of your LAST NAME): A-B
C-H
I-M
N-R
S-Z
Please answer the following questions:
Part I: Multiple Choices (40 pts: 20 @ 2 pts each). Circle the ONE best answer:
1. Which of the following molecules is classified as predominantly ionic?
a) SiO2
b) ClO2
d) P4O10
d) CaO
2. Which of the following molecules have bent (angular) molecular shape?
I) XeF2
II) OF2
III) BeF2
a) I and II
b) only IV
c) only II
d) II and IV
IV) SF2
3. Which of the following ions is expected to be paramagnetic?
a) Zn2+
b) S2-
c) Cu+
d) Co2+
4. Which of the following has the highest first ionization energy?
a) Mg
b) Ca
c) Se
d) Kr
5. The ground state electron configuration of hafnium, Hf (Z = 72) is
a) [Xe] 5d2 6s2
b) [Xe] 4f14 5d2 6s2
c) [Xe] 4f14 6d2 6s2
d) [Xe] 4f14 5d4
6. Consider four identical 1.0 L flasks containing the following gases each at 25 ˚C and 1 atm
pressure. For which gas do the molecules have the highest average velocity?
a) SO2
b) H2
c) O2
d) same for all
7. What type of hybrid orbitals are used by S in SF4?
a) sp
b) sp2
c) sp3
d) sp3d
8. Two solutions, A and B, are labeled “0.10 M CaCl2” and “0.20 M CaCl2”, respectively. Both
solutions contain the same number of moles of CaCl2. If solution A has a volume of 50 mL.
What is the volume of solution B?
a) 100 mL
b) 50 mL
c) 25 mL
d) no answer was given
1
9. The oxidation numbers of phosphorus, P in PH3 and P2O74- are:
10.
a) -3 and +10, respectively
b) -3 and +7, respectively
c) -3 and +5, respectively
d) +3 and +5, respectively
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
11.
b) -2.1 J
c) 0.24 J
d) 130 J
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 4.6 g of Al with
excess oxygen?
a) 8.7 g
b) 17 g
c) 1.2 g
d) 35 g
12. Which of the following molecules is expected to be polar?
a) BeCl2
b) CO2
c) SO2
d) BCl3
13. Which name is incorrect?
a) Mg(NO3)2: magnesium nitrate
b) CoSO4: cobalt(II) sulfate
c) Fe2S3: diiron trisulfide
d) S2F4: disulfur tetrafluoride
14. Which of the following compounds has a triple bond?
a) OPCl2
b) SF4
c) NH3
d) HCN
15. Which of the following molecules is most likely to have bond angle close to 120°?
a) NF3
b) SF4
c) PCl5
d) SO3
16. Which of the following is classified as a weak acid?
a) HBr
b) NaOH
c) MgF2
d) HF
17. Compact disc players use lasers that emit red light with a wavelength of 685 nm. What is the
energy of a mole of photons in kilojoule?
a) 175
b) 2.9 x 10-19
c) 2.73 x 10-13
d) no answer was given
2
18. The assumptions of the kinetic-molecular theory (KMT) are most likely to be correct under what
conditions?
a) high temperature – high pressure
b) high temperature – low pressure
c) low temperature – low pressure
d) always correct
19. Consider the phase diagram for CO2.
In going from point A to B to C:
a) liquid CO2 becomes solid.
b) gaseous CO2 becomes solid.
c) solid CO2 becomes liquid.
d) liquid CO2 becomes gaseous.
20. Consider the phase diagram for CO2.
In going from point A to point B:
a) fusion followed by evaporation
b) fusion followed by sublimation.
c) sublimation followed by condensation.
d) evaporation followed by fusion.
Phase diagram of CO2
Part II. Bonding and Chemical Equations (28 pts):
A) Bonding & molecular structure (14 pts):
1. Draw the Lewis structure for the nitrite ion, NO2-, draw the resonance structures, if there is any then:
predict:
a) the molecular shape of the ion
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: -----------------
3
B) Chemical Equations (14 pts):
1. Write the chemical equation and the net ionic equation for the reaction between aqueous solutions of
Na2SO4 and Ba(OH)2 and then identify the spectator ion(s)
Chemical equation:
Net ionic equation:
Spectator ion(s):
2. Write the balanced chemical equation for the reaction, if any occurs between aqueous solutions of
FeCl3 and NaNO3 (write N.R. if they do not react; no chemical equation)
Chemical equation:
3. Balance the following redox equation in acidic solution:
NO3- (aq) + Cu (s)
NO2 (g) + Cu2+ (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
Part III. Calculations (32 pts: 4 @ 8 pts) Show all work for full credit. Please express all answers
with the proper units and correct number of significant figures.
1. Exactly 20.0 g of SiO2 and 7.00 g of C are allowed to react according to the balanced equation:
SiO2 (s) + 3 C (s)
SiC (s) + 2 CO (g)
a) Determine the limiting reactant then
b) What is the maximum amount of carbon monoxide that can be formed?
a) If you perform the experiment and isolate 4.50 g CO, what is the percent yield?
a) Limiting reactant
b) Theoretical yield of CO
c) Percent yield
5
2. Strychnine, a deadly poison has a molecular mass of 344 and a percentage composition 75.42% C,
6.63% H, 8.38 % N and the balanced oxygen. Determine the simplest and molecular formulas of the
compound.
Simplest Formula
Molecular Formula
C21H22N2O2
C21H22N2O2
3. An important chemical reaction in the manufacture of Portland cement is the higher temperature
decomposition of calcium carbonate to give calcium oxide and carbon dioxide
CaCO3 (s)
CaO (s) + CO2 (g)
Suppose a 1.25 g of CaCO3 is decomposed by heating. How many milliters of CO2 gas will be
evolved, if it will be measured at 740 torr and 25ºC?
Volume of CO2
314 mL
6
4. a) Carbon monoxide is often used in metallurgy to remove oxygen from metal oxides and thereby give
the free metal. The thermochemical equation for the reaction of CO with Fe2O3 is
Fe2O3 (s) + 3 CO (g)
2 Fe (s) + 3 CO2 (g)
∆Hrxn° = ?
Give that ∆Hf° Fe2O3 (s) = -824.2 kJ/mol, ∆Hf° CO (g) = -110.5 kJ/mol and ∆Hf° CO2 (g) = -393.5
kJ/mol, determine the enthalpy change, ∆Hrxn° for the reaction given above.
∆Hrxn° = -26.7 kJ
Bonus Question (5 pts)
Given that:
2 SO3 (g)
2 SO2 (g) + O2 (g)
∆Hrxn° = +198.2 kJ
Calculate ∆H° for the following reaction:
SO2 (g) + ½ O2 (g)
SO3 (g)
∆Hrxn° = -99.1 kJ
7
PREFERENCE SHEET FOR
CHEM 107
Final Exam – Spring 2004
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
1 atm = 760 torr = 760 mmHg
R = 0.0821 L.atm/mol.K
At STP 1 mol of a gas = 22.414 L
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.
8
1
1
2
H
Periodic Table of the Elements
He
1.01
3
2
3
4
5
6
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
21
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
39
Rb Sr Y
22
40
23
41
24
25
26
27
28
29
30
31
32
33
34
35
18
36
Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
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
54
Xe
85.47 87.62 88.91 91.22 92.91 95.94 (98)
101.1 102.9 106.4 107.9 112.4 114.8 118.7 121.8 127.6 126.9 131.1
55
76
56
57
72
73
74
75
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)
9
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