NAME:____________________________
Fall 2011
INSTRUCTIONS:
Student Number:______________________
Chemistry 2000 Midterm #2A
____/ 40 marks
1) Please read over the test carefully before beginning. You should have 6 pages of
questions and a formula/periodic table sheet.
2) If your work is not legible, it will be given a mark of zero.
3) Marks will be deducted for incorrect information added to an otherwise correct
answer.
4) Marks will be deducted for improper use of significant figures and for missing or
incorrect units.
5) Show your work for all calculations. Answers without supporting calculations will
not be given full credit.
6) You may use a calculator.
7) You have 90 minutes to complete this test.
Confidentiality Agreement:
I agree not to discuss (or in any other way divulge) the contents of this exam until after 6:30 pm Mountain Time
on Wednesday, November 16th, 2011. I understand that breaking this agreement would constitute academic
misconduct, a serious offense with serious consequences. The minimum punishment would be a mark of 0/40
on this exam and removal of the “overwrite midterm mark with final exam mark” option for my grade in this
course; the maximum punishment would include expulsion from this university.
Signature: ___________________________
Course: CHEM 2000 (General Chemistry II)
Semester: Fall 2011
The University of Lethbridge
Date: _____________________________
Question Breakdown
/6
Q1
/8
Q2
/7
Q3
/6
Q4
/3
Q5
/ 10
Q6
Total
1/7
/ 40
NAME:____________________________
1.
Student Number:______________________
Calculate the root-mean-squared speeds of an NO2 and of an N2O4 molecule at 35 °C. Sketch the
distribution of speeds for both molecules in one graph (number of molecules versus molecular speed).
[6 marks]
2/7
NAME:____________________________
Student Number:______________________
2.
(a)
[8 marks]
Draw the Lewis structures for XeF2 and SF2.
(b)
What are the molecular geometries of XeF2 and SF2?
(c)
For each compound, name the strongest intermolecular force that would be present in a pure sample.
(d)
Xenon difluoride is a solid, while SF2 is a gas. Is this observation in agreement or disagreement with
your answer for (c)? Explain your answer.
3.
Is HClO2 a strong or a weak acid at exactly 25 °C? Calculate its pKa value to decide. (Reminder: a
strong acid has a pKa value <0)
[7 marks]
3/7
NAME:____________________________
4.
Student Number:______________________
The boiling point of pure water in Lethbridge (atmospheric pressure = 89.3 kPa) is 96.7 °C.
[6 marks]
(a) What is the vapour pressure of pure water in Lethbridge at 96.7 °C?
(b) What is the vapour pressure of water of an aqueous solution prepared from 0.50 mol MgCl2 and
1.000 kg of water at 96.7 °C in Lethbridge?
5.
Two dice, each number 1 – 6, are rolled. What is the entropy associated with rolling a 10?
[3 marks]
4/7
NAME:____________________________
6.
Student Number:______________________
Calculate the cell potential for the following electrochemical cell at exactly 25°C in a basic solution.
Based on your calculation, does this electrochemical cell describe a spontaneous process?
Pt(s)|ClO‒(aq) (0.00105 M), ClO3‒(aq) (0.120 M)|| ClO‒(aq) (0.00105 M), Cl‒(aq) (0.200 M)|Pt(s)
[10 marks]
5/7
NAME:____________________________
Student Number:______________________
Some Useful Constants and Formulae
Fundamental Constants and Conversion Factors
Atomic mass unit (u)
1.6605  10-27 kg
Avogadro's number (NA) 6.02214  1023 mol–1
Boltzmann constant (kB) 1.38065  10-23 J·K-1
Ideal gas constant (R)
8.3145 J·mol-1·K-1
8.3145 m3·Pa·mol-1·K-1
Faraday’s constant (F)
96485 C∙mol‒1
Kelvin temperature scale
Planck's constant (h)
Speed of light in vacuum (c)
Pressure conversions
0 K = ‒273.15 ˚C
6.626  10-34 J·Hz-1
2.9979 x 108 m·s-1
1 bar = 100 kPa
1 atm = 1.01325 bar
Formulae
v rms
3RT
 v 
M
PV  nRT
2
S  k B ln 
S 
q rev
T
 r Gm   r Gmo  RT lnQ
pH   log aH 
 r Gm   e FE
E  E 
Ideal Solute
Ideal Gas
 r G   r H  T r S
 r Gmo  RT ln K
pK a   log K a
Activities
Solid
Pure liquid
Ideal Solvent

n2 
 P  a 2 V  nb  nRT
V 

PA  X A PA
RT
ln Q
eF
a 1
a 1
aX
c
a
c
P
a
P
6/7
 K   Ho
ln 2   r m
R
 K1 
[ A]  k H PA
1
1
  
 T1 T2 
X 
n
n
NAME:____________________________
1
Student Number:______________________
Chem 2000 Standard Periodic Table
18
1.0079
4.0026
He
H
2
13
14
15
16
17
6.941
9.0122
10.811
12.011
14.0067
15.9994
18.9984
Li
Be
B
C
N
O
F
Ne
3
22.9898
4
24.3050
5
26.9815
6
28.0855
7
30.9738
8
32.066
9
35.4527
10
39.948
1
2
20.1797
Na
Mg
11
39.0983
12
40.078
3
4
5
6
7
8
9
10
11
12
44.9559
47.88
50.9415
51.9961
54.9380
55.847
58.9332
58.693
63.546
65.39
K
Ca
Sc
Ti
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
Ga
Ge
As
Se
Br
Kr
19
85.4678
20
87.62
21
88.9059
22
91.224
23
92.9064
24
95.94
26
101.07
27
102.906
28
106.42
29
107.868
30
112.411
31
114.82
32
118.710
33
121.757
34
127.60
35
126.905
36
131.29
Rb
Sr
37
132.905
38
137.327
Cs
Ba
55
(223)
56
226.025
Fr
87
Ra
Y
39
La-Lu
Ac-Lr
88
P
S
Cl
Ar
15
74.9216
16
78.96
17
79.904
18
83.80
Zr
Nb
Mo
Tc
Ru
Rh
Pd
Ag
Cd
In
Sn
Sb
Te
I
Xe
41
180.948
42
183.85
43
186.207
44
190.2
45
192.22
46
195.08
47
196.967
48
200.59
49
204.383
50
207.19
51
208.980
52
(210)
53
(210)
54
(222)
Hf
Ta
W
Re
Os
Ir
Pt
Au
72
(261)
73
(262)
74
(263)
75
(262)
76
(265)
77
(266)
78
(281)
79
(283)
Rf
Db
Sg
105
106
138.906
140.115
140.908
144.24
La
Ce
Pr
Nd
57
227.028
58
232.038
59
231.036
60
238.029
Ac
Si
14
72.61
40
178.49
104
89
25
(98)
Al
13
69.723
Th
90
Pa
91
U
92
Bh
107
Hs
Mt
Dt
Hg
Tl
Pb
Bi
Po
81
82
83
84
85
174.967
Rg
108
109
110
111
(145)
150.36
151.965
157.25
158.925
162.50
164.930
167.26
168.934
173.04
Pm
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
61
237.048
62
(240)
63
(243)
64
(247)
65
(247)
66
(251)
67
(252)
68
(257)
69
(258)
70
(259)
71
(260)
Np
93
Pu
94
Am
95
Cm
96
Bk
97
Cf
98
Es
99
Fm
100
Md
101
No
102
Developed by Prof. R. T. Boeré
Thermodynamic Data
ClO  (aq)
 kJ 
 f H mo 

 mol 
‒107.1
 kJ 
 f Gmo 

 mol 
‒36.8
ClO3( aq)
‒104
‒3.0
‒167.1
‒131.0
HClO2( aq)
‒51.9
5.9
ClO2( aq)
‒66.5
17.2
H 2 O(l )
‒285.8
‒237.1
H 2 O( g )
‒241.8
‒228.6
H 3O(aq)
‒285.83
‒237.1

Cl(aq
)
At
80
7/7
Lr
103
Rn
86