CHEM 107 (Spring-2007)
Exam 2 (104 pts)
Name: ------------------------------------------------------------------------, Clid # -----------------------------LAST NAME, First
(Circle the alphabet segment of your LAST NAME): A & B
C-G
H-L
M-P
R-Z
Please answer the following questions:
Part I: Multiple Choices (52 pts: 12 @ 4 pts each + 4 pts bonus). Circle the ONE best answer:
1. Which of the following is strong electrolyte?
a) acetic acid, HC2H3O2
b) nitric acid, HNO3
c) aqueous ammonia, NH3 (aq)
d) sugar
2. Which of the following equations DO NOT represent an oxidation?
a) SO2
SO3
b) Mg
Mg2+
c) MnO2
Mn2+
d) 2 Br-
Br2
3. The oxidation states of chlorine in ClO2- and Cl2O7 are:
a) –1 and –7, respectively
b) +1 and –7, respectively
c) -1 and +7, respectively
d) +3 and +7, respectively
4. For the reaction: Zn (s) + 2 HCl (aq)
ZnCl2 (aq) + H2 (g), the spectator ion(s) are:
a) Zn2+ and Cl-
b) Zn2+ and H+
c) Cl- and H+
d) only Cl-
5. In the reaction:
CaCO3 (s) + 2 HCl (aq)
CaCl2 (aq) + H2O (aq) + CO2 (g)
What volume of 6.0 M HCl will be needed to react with 0.350 mol of CaCO3?
a) 117 mL
b) 42.0 mL
c) 1.17 L
d) 583 mL
6. 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 O2?
a) 8.7 g
b) 17.4 g
c) 4.3 g
d) no answer was give
7. Which of the following salts are expected to be soluble in water?
a) Ca3(PO4)2
b) BaSO4
c) Na2S
d) PbI2
1
8. 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
9. How many molecules of hydrogen sulfide, H2S are contained in 0.50 L of H2S at 1 atm and 27 ˚C?
a) 1.34 x 1022
b) 3.00 x 1022
c) 1.22 x 1022
d) 2.03 x 10-2
10. 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
11. 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
12. Assuming ideal gas behavior. Which of the following statements is INCORRECT?
a) The pressure of the gas results from the collisions of the gas molecules with the wall of the
container.
b) The volume occupied by a gas depends on its temperature, pressure and number of moles.
c) When the temperature of a gas sample is increased at constant pressure, the density of the
gas will decrease.
d) In a mixture containing O2 and N2 molecules, the O2 molecules, on the average are moving
faster than the N2 molecules.
13. The gas pressure in an aerosol can is 1.5 atm at 25ºC. Assuming the gas inside obeys the ideal
gas equation, what would the pressure be if the can were heated to 450ºC?
a) 3.6 atm
b) 27 atm
c) 0.62 atm
d) 0.083 atm
Part II. Equations and formulas (20 pts)
In the following section please include the physical states as (s, l, g aq) for reactants and products. Use the
periodic chart for charges on each ion and reference sheet. Please write N. R. if there is no reaction.
1. (4 pts) Write the balanced chemical equation for the reaction, if any occurs between aqueous solutions
of KNO3 and Na2CO3 (write N.R. if they do not react; no chemical equation)
Chemical equation:
2
2. (6 pts) Write the balanced chemical equation and the net ionic equation for the reaction between
aqueous solutions of Pb(NO3)2 and NaI, and then identify the spectator ion(s)
Chemical equation:
Net ionic equation:
Spectator ion(s):
3. (10 pts) Balance the following redox equation in acidic solution:
SO32- (aq) + MnO4- (aq)
SO42- (aq) + Mn2+ (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: -------Part III. Calculations (32 pts) Show all work for full credit. Please express all answers with the
proper units and correct number of significant figures.
1. (8 pts) 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
2. (12 pts) 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
2. (12 pts) Phosphorus trichloride, PCl3, is a commercially important compound used in the manufacture
of pesticides, gasoline additives, and a number of other products. It is made by the direct
combination of phosphorus and chlorine according to the equation below?
P4 (s) + 6 Cl2 (l)
4 PCl3 (l)
a) Determine the limiting reactant if 125 g P4 was mixed with 323 g Cl2.
b) If 378 g of PCl3 was obtained, then what is the %yield of the reaction?
a) L. R.: Cl2
b) 417 g, % yield = 90.6
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PREFERENCE SHEET FOR
CHEM 107
Exam 2 – Spring 2007
You will have 65 minutes to complete this exam. The exam has 4 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
PV = nRT
K.E. = ½ mv2
1/2
Average speed of a gas, u = (3RT/M)
Rate of effusion of B/Rate of effusion of A = (MA/MB)1/2
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.
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)
5