Chemistry 121A Hanson
EXAM 2
Fall 2014
Name___________________________
CALCULATORS ARE ALLOWED ON THIS EXAM
NOTE: To receive credit, show your work.
If you feel strapped for time, try to at least start each problem before going on to the next.
PLEASE DO NOT OPEN THE EXAM UNTIL INSTRUCTED TO DO SO
1
1A
18
8A
1
2
2
2A
13
3A
14
4A
15
5A
16
6A
17
7A
4.003
5
6
7
8
9
10
Li
4
Be
B
C
N
O
F
Ne
6.941
9.012
10.81
12.01
14.01
16.00
19.00
20.18
11
12
13
14
15
16
17
18
H
1.008
3
He
4
4B
5
5B
6
6B
7
8
9
10 11
7B ———8B——— 1B
12
2B
Si
P
S
24.31
3
3B
Al
22.99
26.98
28.09
30.97
32.07
35.45
39.95
19
20
21
22
23
24
25
30
31
32
33
34
35
36
Na Mg
K
26
27
28
29
Cl Ar
Ca Sc
Ti
V
39.10
40.08
44.96
47.88
50.94
52.00
54.94
55.85
58.93
58.69
63.55
65.39
69.72
72.61
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
Sn Sb Te
I
Xe
Rb Sr
85.47
87.62
55
56
Cs Ba
132.91 137.33
87
88
Y
Zr Nb Mo Tc Ru Rh Pd Ag Cd In
88.91
91.22
92.91
95.94
(98)
71
72
73
74
75
*
101.07 102.91 106.42 107.87 112.41 114.82 118.71 121.76 127.60 126.90 131.29
76
77
78
Lu Hf Ta W Re Os
Ir
Pt Au Hg Tl Pb Bi
174.97 178.49 180.95 183.85 186.21
190.2
†
(223) 226.03
(260)
80
81
192.22 195.08 196.97 200.59 204.38
Lr Rf Db Sg Bh Hs Mt
(261)
Lanthanide Series
(260)
(263)
(262)
(265)
(266)
?
?
?
57
58
59
60
61
62
63
64
Actinide Series
65
82
207.2
83
208.98
84
85
86
Po At Rn
(209)
(210)
(222)
114
116
118
?
?
?
66
67
68
69
70
La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb
138.91 140.12 140.91 144.24
†
79
103 104 105 106 107 108 109 110 111 112
Fr Ra
*
Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
89
90
(145)
150.36 151.96 157.25 158.93 162.50 164.93 167.26 168.93 173.04
91
92
93
Ac Th Pa
U
Np Pu Am Cm Bk Cf Es Fm Md No
227.03 232.04 231.04 238.03 237.05
94
(244)
95
(243)
96
(247)
97
(247)
98
(251)
99
(252)
100 101 102
(257)
(258)
(259)
Avogadro’s Number: 6.02214 x 1023
(5 points extra credit) Elementary Discoveries
Four scientists, Cavendish, Moisson, Priestley, and Rutherford, discovered four elements, fluorine (F2),
hydrogen (H2), nitrogen (N2), and oxygen (O2). Each of these elements has a different property: One is
among the least reactive elements, one is the most reactive element, one is the most abundant element in
the body, and one is the most abundant element in the universe. Can you determine who discovered
what element and what each element’s property is?
a. Fluorine, which was not discovered by Cavendish, isn’t the least reactive element.
b. Nitrogen, which was not discovered by Priestley, isn’t the most abundant element in the universe.
c. The four scientists are: Priestley, Rutherford, the discoverer of fluorine, and the discoverer of the
element most abundant in the universe.
d. The element found to be the most abundant in the body wasn’t discovered by Moisson and isn’t
nitrogen or hydrogen.
(15) 1.
a.
b.
c.
(20) 2.
a.
Balance the following chemical equations:
CO +
H2O 

C2H2 +
the equation for the full combustion of C2H6
K2Cr2O7 +
HI +
HClO4 

Cr(ClO4)3 +
I2 +
 NaClO (aq) + 5 NaCl (aq) + 3 H2O
Cl2 (aq) + 6 NaOH (aq) 
(1) [S W N]
[S W N]
[S W N]
[S W N]
(3) net ionic equation:
mixing of Na2SO4 (aq) and Cr(ClO4)3 (aq)
(1)
[S W N]
[S W N]
(2) principal reactant species in solution:
(3) net ionic equation:
/35
KClO4 +
H2O
For each of the following, (1) label each substance involved as a strong electrolyte (S), a weak
electrolyte (W), or a nonelectrolyte (N); (2) list the principal reactant species in solution, and (3) write
the balanced net ionic equation.
(2) principal reactant species in solution:
b.
O2
(25) 3.
Calculate:
a.
The number of atoms of 35Cl in 10.0 g of natural abundance Cl2. (Natural chlorine is
75.78% 35Cl and 24.22% 37Cl.) [HINT: Think first. Full answer can easily fit in the space below.]
b.
The empirical formula of a compound containing only platinum (Pt) and chlorine (Cl) if analysis
indicates that it is 42.09% Cl.
c.
The mass of F2 that is needed to produce 100.0 g of IF7 according to the equation:
 2 IF7
I2 + 7 F2 
d.
/25
The limiting reactant and theoretical yield in the reaction given above in part (c) if 65.0 g I2 is reacted
with 10.0 g of F2.
(24) 4.
/24
Explain…
a.
…the difference between a chemical reaction and a chemical equation, giving two characteristics of
each.
b.
…the basic idea of how a mass spectrometer works, and what it is good for
c.
…what green chemistry means.
(16) 5.
Soon after graduation, a St. Olaf Student, Arnt I. Gud, got a $2000-per-day job as a consultant for a
company that works with a variety of metals and had messed up by accidentally mixing several gallons
of them. The company needed to know how they should go about separating the metals. Testing three
standard solutions of silver(I), lead(II), and iron(III), he found: (“precip” indicates precipitate.)
Reagents:
0.1 M
HCl
0.1 M
H2SO4
0.1 M
NaOH
0.1 M
NH3
0.1 M
KSCN
Metal ion solutions
0.1 M AgNO3
white precip
no reaction
white precip
white precip
white precip
0.1 M Pb(NO3)2
white precip
white precip
white precip
white precip
white precip
yellow
solution
red-brown
precip
red-brown
precip
0.1 M Fe(NO3)3
yellow
solution
dark red
solution
Arnt then proceeded to add one drop of one of the reagents and one drop of another to a sample of the
mixture, observed a reaction, and exclaimed, “Ah, ha! I know what it is!” What did Arnt report to his client?
Be sure to include and identify ALL solids and all species present in solution at the end of the procedure in the
recommendation. If the final solution contains acid, indicate that it needs to be “neutralized with base”; if it
contains base, indicate that it needs to be “neutralized with acid.”
I, the undersigned, as a certified Ag-Pb-Fe handler, have found the material
given to me for disposal or recycling to contain the checked ions:
 Ag+
 Pb2+
 Fe3+
As such, my recommended handling procedure is outlined below:
signature _____________________________ date _____________
PLEDGE: I pledge my honor that on this examination I have neither given nor received assistance not explicitly approved by
the professor and that I have seen no dishonest work.
[ ] I intentionally did not sign the pledge.
Signature______________________________