Download Exam V Spring 2002

CHEM 1515.001 - 006
Exam !V
John V. Gelder
May 6, 2002
Name ________________________
TA's Name ________________________
Section _______
INSTRUCTIONS:
1. This examination consists of a total of 11 different pages.
The last four pages include a periodic table; many useful
equations and constants; a table of vapor pressures for
water; a solubility table; a table of equilibrium constants for
acids and bases; and a table of thermodynamic values. All
work should be done in this booklet.
2. PRINT your name, TA's name and your lab section
number now in the space at the top of this sheet. DO
NOT SEPARATE THESE PAGES.
3. Answer all questions that you can and whenever called
for show your work clearly. Your method of solving
problems should pattern the approach used in lecture.
You do not have to show your work for the multiple
choice or short answer questions.
4. No credit will be awarded if your work is not shown in 6.
5. Point values are shown next to the problem number.
6. Budget your time for each of the questions. Some
problems may have a low point value yet be very
challenging. If you do not recognize the solution to a
question quickly, skip it, and return to the question after
completing the easier problems.
7. Look through the exam before beginning; plan your
work; then begin.
8. Relax and do well.
SCORES
Page 2
Page 3
Page 4
Page 5
Page 6
Page 7
TOTAL
_____
(18)
_____
(16)
_____
(16)
_____
(18)
_____
(20)
_____
(12)
______
(100)
CHEM 1515 EXAM V
(9)
PAGE 2
1. Write the chemical formula(s) of the product(s) and balance the following reactions. Identify all products
phases as either (g)as, (l)iquid, (s)olid or (aq)ueous. Soluble ionic compounds should be written in the
form of their component ions.
a)
Zn(NO3)2(aq)
+
b)
Na2CO3(s)
c)
(CH3)2NH(aq)
+
Na2S(aq) Æ
HCl(aq) Æ
+
HCN(aq) Æ
(4) 2a. Write the ionic and net ionic chemical equation for 1a), 1b) or 1c).
Ionic equation
Net Ionic equation
(5)
3. Account for the following observations about NH3 and NF3. In your answer, use appropriate principles
of intermolecular forces. Your answer must include reference to both substances.
a)
NH3 has a normal boiling point of –33.4 ˚C where as NF3 has a boiling point of –128.8 ˚C.
CHEM 1515 EXAM V
PAGE 3
(16) 4.
0.10 M
NaF
0.10 M
MgCl2
0.10 M
C2H5OH
0.10 M
CH3COOH (HC2H3O2)
Answer the following questions, which refer to the 100 mL samples of aqueous solutions at 25 ˚C in the
stoppered flasks shown above
(a) Which solution has the lowest electrical conductivity? Explain.
(b) Which solution has the lowest freezing point? Explain.
(c) Above which solution is the pressure of water vapor the greatest? Explain.
(d) Which solution has the highest pH? Explain.
CHEM 1515 EXAM V
PAGE 4
(16) 5a. Define the term 'equilibrium vapor pressure'.
(b)
If a sample of a liquid is injected into an evacuated container, describe what phase change occurs.
(Note the amount of the liquid injected is small compared to the volume of the container.)
(c)
Is the phase change exothermic or endothermic? Explain?
(d)
In terms of the 'pressure exerted by the vapor' and the 'equilibrium vapor pressure' how do we
determine what phase(s) are present in the container after adding the sample?
CHEM 1515 EXAM V
PAGE 5
(18) 6. A commercial aqueous solution of ammonia is 28% NH3 by mass and has a density of 0.900 g mL-1.
(a) Calculate the molarity of the solution.
(b) Calculate the molality of the solution.
(c) Describe how you would prepare 1.00 L of a 0.400 M NH3 solution from the more concentrated
solution in part a).
CHEM 1515 EXAM V
PAGE 6
6. (CONTINUED)
(10) (d) Calculate the pH of the solution prepared in part c)
.
(10) (e) Calculate the pH of the solution prepared by adding 0.250 mol of solid NH4Cl to the solution prepared
in part c).
CHEM 1515 EXAM V
PAGE 7
(12) 7. For the gaseous equilibrium represented below, it is observed that greater amounts of PCl3 and Cl2 are
produced as the temperature is increased.
PCl3(g) ä PCl3(g) + Cl2(g)
(a)
What is the sign of ∆S˚ for the reaction? Explain.
(b)
What change, if any, will occur in ∆G˚ for the reaction as the temperature is increased? Explain
your reasoning in terms of thermodynamic principles.
(c)
If the volume of the reaction mixture is decreased at constant temperature to half the original
volume, what will happened to the number of moles of Cl2 in the reaction vessel? Explain.
CHEM 1515 EXAM V
PAGE 8
Periodic Table of the Elements
IA
VIIIA
1
1
H
1.008
3
2
He
IIA
IIIA IVA VA VIA VIIA 4.00
4
5
Li Be
2
B
6.94 9.01
11
12
Na Mg
3
22.99 24.30
19
20
4
5
6
7
6
7
8
9
10
C
N
O
F Ne
Al Si
P
S
Cl Ar
31
33
34
35
10.81 12.01 14.01 16.00 19.00 20.18
13
14
15
16
17
18
IIIB IVB VB VIB VIIB
21
22
K Ca Sc Ti
23
24
25
VIII
26
27
IB
28
29
IIB 26.98 28.09 30.97 32.06 35.45 39.95
30
32
36
V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
39.10 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
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
Rb Sr
Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te
I
Xe
85.47 87.62 88.91 91.22 92.91 95.94 (98) 101.1 102.9 106.4 107.9 112.4 114.8 118.7 121.8 127.6 126.9 131.3
55
56
57
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
Cs Ba La Hf Ta W Re Os Ir
Pt Au Hg Tl Pb Bi Po At Rn
132.9 137.3 138.9 178.5 180.9 183.8 186.2 190.2 192.2 195.1 197.0 200.6 204.4 207.2 209.0 (209) (210) (222)
87
88
89 104 105 106
Fr Ra Ac
(223) 226.0 227.0 (261) (262) (263)
Lanthanides
Actinides
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
93
94
95
96
97
98
99 100 101 102 103
Th Pa U
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)
Useful Information
L·atm
J
PV = nRT
R = 0.0821 mol·K = 8.314 mol·K
Ê vp2ˆ
∆H˚vap Ê 1
1ˆ
g
lnÁË vp1˜¯ = – R ÁË T2!–!T1˜¯
density of H2O = 1.00 3
cm
∆H˚rxn = ∑n(∆Hf˚(products)) – ∑ m(∆Hf˚(reactants))
6.02 x 1023
∆S˚rxn = ∑ n(S˚(products)) – ∑ m(S˚(reactants))
∆G˚rxn = ∑ n(∆Gf˚(products)) – ∑ m(∆Gf˚(reactants))
∆G˚ = ∆H˚ - T∆S˚
pH = –log[H+ ]
∆G˚ = –RTlnK
x1,2 =
pH + pOH = 14
Kp = Kc(RT)∆n
–b± b2!–!4ac
for ax2 + bx + c = 0
2a
pOH = –log [OH–]
Kw = 1.00 x 10–14
CHEM 1515 EXAM V
PAGE 9
1 pm = 10-12 m
Psolution = csolventP˚solvent
∆T = ikm
˚C
kf(H2O) = 1.86 m
edge length (l) = 2r
˚C
kb(H2O) = 0.512 m
edge length (l) = 2 2· r
Temperature (°C)
-5
0
5
10
15
20
25
30
35
40
45
Vapor
Pressure(mmHg)
3.2
4.6
6.52
9.20
12.8
17.5
23.8
31.8
42.1
55.3
71.9
edge length (l) =
Temperature (°C)
50
55
60
65
70
75
80
85
90
95
100
4r
3
Vapor
Pressure(mmHg)
92.5
118.0
149.4
187.5
233.7
289.1
355.1
433.6
525.8
633.9
760
Solubility Table
Ion
NO3–
ClO4–
Cl–
I–
SO42–
Solubility
soluble
soluble
soluble
soluble
soluble
Exceptions
none
none
except Ag+ , Hg22+, *Pb2+
except Ag+ , Hg22+, Pb2+
except Ca2+, Ba2+, Sr2+, Hg2+, Pb2+, Ag+
CO32–
insoluble
except Group IA and NH4
PO43–
-OH
S2–
Na+
NH4+
K+
insoluble
insoluble
insoluble
soluble
soluble
soluble
except Group IA and NH4
except Group IA, *Ca2+, Ba2+, Sr2+
except Group IA, IIA and NH4+
none
none
none
*slightly soluble
+
+
CHEM 1515 EXAM V
Name
PAGE 10
Formula
Ka1
Acetic
Ascorbic
HC2 H3 O2
Arsenic
H3 AsO4
1.8 x 10– 5
8.0 x 10– 3
5.6 x 10– 3
Arsenous
Benzoic
Boric
Butyric acid
Carbonic
Cyanic
Citric
H3 AsO3
HC7 H5 O2
H3 BO3
HC4 H7 O2
H2 CO3
HCNO
H3 C6 H5 O7
6.0
6.5
5.8
1.5
4.3
3.5
7.4
Formic
Hydroazoic
Hydrocyanic
Hydrofluoric
Hydrogen chromate ion
Hydrogen peroxide
Hydrogen selenate ion
Hydrogen sulfate ion
Hydrogen sulfide
Hypobromous
Hypochlorous
Hypoiodus
Iodic
Lactic
Malonic
Oxalic
HCHO2
HN3
HCN
HF
HCrO4 –
H2 O2
HSeO4 –
HSO4 –
H2 S
HBrO
HClO
HIO
HIO3
HC3 H5 O3
H2 C3 H2 O4
H2 C2 O4
1.8
1.9
4.9
7.2
3.0
2.4
2.2
1.2
5.7
2.0
3.0
2.0
1.7
1.4
1.5
5.9
Nitrous
Phenol
Phosphoric
Paraperiodic
Propionic
Pyrophosphoric
Selenous
Sulfuric
Sulfurous
Tartaric
HNO2
HC6 H5 O
H3 PO4
H5 IO6
HC3 H5 O2
H4 P2 O
H2 SeO3
H2 SO4
H2 SO3
H2 C4 H4 O6
E.2
HC6 H7 O6
10– 1 0
10– 5
10– 1 0
10– 5
10– 7
10– 4
10– 4
x 10– 4
x 10– 5
x 10– 1 0
x 10– 4
x 10– 7
x 10– 1 2
x 10– 2
x 10– 2
x 10– 8
x 10– 9
x 10– 8
x 10– 1 1
x 10– 1
x 10– 4
x 10– 3
x 10– 2
x 10– 4
x
x
x
x
x
x
x
4.5
1.3 x
7.5 x
2.8 x
1.3 x
3.0 x
2.3 x
strong
1.7 x
1.0 x
10– 1 0
10– 3
10– 2
10– 5
10– 2
10– 3
acid
10– 2
10– 3
Ka2
Ka3
1.0 x 10– 7
3.0 x 10– 1 2
5.6 x 10– 1 1
1.7 x 10– 5
4.0 x 10– 7
1.3 x 10– 1 3
2.0 x 10– 6
6.4 x 10– 5
6.2 x 10– 8
5.3 x 10– 9
4.4
5.3
1.2
6.4
4.6
x
x
x
x
x
4.2 x 10– 1 3
10– 3
10– 9
10– 2
10– 8
10– 5
DISSOCIATION CONSTANTS FOR BASES AT 25˚C
Name
Formula
Ammonia
Aniline
Dimethylamine
Ethylamine
Hydrazine
NH3
C6 H5 NH2
(CH3 )2 NH
C2 H5 NH2
H2 NNH2
Kb
1.8
4.3
5.4
6.4
1.3
x
x
x
x
x
10– 5
10– 1 0
10– 4
10– 4
10– 6
Name
Formula
Hydroxylamine
Methylamine
Pyridine
Trimethylamine
HONH2
CH3 NH2
C5 H5 N
(CH3 )3 N
Kb
1.1
4.4
1.7
6.4
x
x
x
x
10– 8
10– 4
10– 9
10– 5
CHEM 1515 EXAM V
PAGE 11
Thermodynamic Values (25 ˚C)
Substance
and State
Carbon
C(s) (graphite)
C(s) (diamond)
CO(g)
CO2 (g)
CH4 (g)
CH3 OH(g)
CH3 OH(l)
CH3 Cl(g)
CHCl3 (g)
CHCl3 (l)
H2 CO(g)
HCOOH(g)
HCN(g)
C2 H2(g)
C2 H4 (g)
CH3 CHO(g)
C2 H5 OH(l)
C2 H6 (g)
C3 H6 (g)
C3 H8 (g)
Bromine
Br2 (l)
BrCl(g)
o!
o!
So
Substance
Ê J ˆ
Ë K. mol¯
and State
DH f
Ê kJ ˆ
Ë mol¯
DG f
Ê kJ ˆ
Ë mol¯
0
2
-110.5
-393.5
?
-201
-239
-80.8
-100.8
-131.8
-116
-363
135.1
227
52
-166
-278
-84.7
20.9
-104
0
3
-137
-394
-51
-163
-166
-57.4
6
2
198
214
186
240
127
234
-110
-351
125
209
68
-129
-175
-32.9
62.7
-24
219
249
202
201
219
250
161
229.5
266.9
270
0
14.64
0
-0.96
152.
240
Chlorine
Cl2 (g)
Cl2 (aq)
Cl-(aq)
HCl(g)
0
-23
0
7
223
121
-167
-92
-131
-95
57
187
Fluorine
F2 (g)
F-(aq)
HF(g)
0
-333
-271
0
-279
-273
203
-14
174
Hydrogen
H2 (g)
H(g) 217
H+(aq)
OH-(aq)
H2 O(l)
H2 O(g)
Magnesium
Mg(s)
Mg(aq)
MgO(s)
0
203
0
-230
0
115
0
-157
131
-242
-229
189
0
-492
-601
0
-456
-569
33
-118
26.9
0
-11
o!
o!
So
DH f
Ê kJ ˆ
Ë mol¯
DG f
Ê kJ ˆ
Ë mol¯
0
232
143
0
161
163
205
Nitrogen
N2 (g)
NCl3 (g)
NF3 (g)
NH3 (g)
NH3 (aq)
NH2 CONH2 (aq)
NO(g)
NO2 (g)
N2 O(g)
N2 O4 (g)
N2 O5 (g)
HNO3 (aq)
HNO3 (l)
NH4 Cl(s)
NH4 ClO4 (s)
0
230
-125
?
?
?
90
32
82
10
-42
-207
-174
-314
-295
0
271
-83.6
-17
-27
?
87
52
104
98
134
-111
-81
-201
-89
192
-137
-139
193
111
174
211
240
220
304
178
146
156
95
186
Silver
Ag(s)
Ag+(aq)
Ag(S2 O3 )3-(aq)
AgBr(s)
AgCl(s)
0
105.6
-1285.7
-100.4
-127.1
0
77.1
--96.9
-109.8
42.6
72.7
-107.1
96.2
Oxygen
O2 (g)
O(g) 249
O3 (g)
Ê J ˆ
Ë K. mol¯
239
Sulfur
S(rhombic)
SO2 (g)
SO3 (g)
H2 S(g)
0
-296.8
-395.7
-20.17
0
-300.2
-371.1
-33.0
31.8
248.8
256.3
205.6
Titanium
TiCl4 (g)
TiO2 (s)
-763
-945
-727
-890
355
50
Aluminum
AlCl3 (s)
-526
-505
184
Barium
BaCl2 (aq)
-872
Ba(OH)2 ·8H2 O(s) -3342
-823
-2793
123
427
Iodine
I2 (s)
HI(g)
0
25.94
0
1.30
116.7
206.3