Download 2012 Chem 13 News Exam

CHEM 13 NEWS EXAM 2012
UNIVERSITY OF WATERLOO
DEPARTMENT OF CHEMISTRY
10 MAY 2012
TIME: 75 MINUTES
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It is the Data Sheet.
1
Which statement about the properties of water is
incorrect?
5
3
4
2
2
6
2
6
10
2
5
2
2
6
2
6
2
5
2
2
6
2
6
2
5
10
2
2
6
2
6
2
6
2
2
2
6
2
6
10
A
Water expands as it freezes.
A
1s 2s 2p 3s 3p 3d 4s 4p
B
The density of water is greater than that of ice.
B
1s 2s 2p 3s 3p 4s 4p
C
Water is a good solvent for hydrocarbons of high
molecular weight.
C
1s 2s 2p 3s 3p 4s 4p 4d
D
1s 2s 2p 3s 3p 4s 4p 5s 5p
E
1s 2s 2p 3s 3p 3d 4s 4p
D
Water molecules are V-shaped (bent).
E
Water has the highest boiling point of all the
group 16 hydrides.
6
2
What is the electron configuration of bromine (Br) in its
lowest energy state?
Which of the following statements accounts for the
observation that, at 300 K and 10 atm, the molar
volume of C2H6(g) is less than that of H2(g)?
1
5
6
The following exothermic reaction reaches equilibrium
in a closed reaction vessel.
4 HF(aq) + CoO2(s)
 F2(g) + 2 H2O(l) + Co2+(aq) + 2 F −(aq)
Which of the following actions causes net reaction
from left to right?
A
C2H6 molecules are smaller than H2 molecules.
B
The average kinetic energy of H2 molecules is
greater than that of C2H6 molecules.
A
adding something that reacts with Co (aq)
C
The average kinetic energy of H2 molecules is
less than that of C2H6 molecules.
B
increasing the temperature
D
The intermolecular attractions in C2H6(g) are
weaker than they are in H2(g).
C
adding some soluble fluoride salt, such as NaF(s)
D
adding a catalyst
E
The intermolecular attractions in C2H6(g) are
stronger than they are in H2(g).
E
decreasing the volume of the reaction vessel
In which compound does manganese have the lowest
oxidation state?
A
MnO2
B
MnI2
C
K2MnO4
D
Mn2O7
E
KMnO4
7
O2(g)
2 Cu(s) + O2(g)  2 CuO(s)
1.8 × 10
−3
−3
B
3.6 × 10
C
7.2 × 10
E
1
2
what is K for the reaction shown below?
+
D
Given the following reactions and equilibrium
constants
K1
4 Cu(s) + O2(g)  2 Cu2O(s)
2 CuO(s)  Cu2O(s) +
How many moles of K ions are there in 0.12 L of
−1
0.015 mol L K2SO4(aq)?
A
2+
−3
−3
9.4 × 10
−3
5.4 × 10
mol
mol
mol
A
K = K1 K 2
B
K=
K1 K 2
C
K=
K1 K 2
D
K=
K 2 K1
E
K = K1 K 2
mol
mol
2 /CHEM 13 NEWS EXAM © 2012 UNIVERSITY OF WATERLOO
K2
8
9
Which of the following has three unpaired electrons
in its lowest energy state?
12 In the SOCl2 molecule, the S atom is the central atom
and O and Cl atoms are bonded directly to S. What is
the Cl-S-Cl angle in the SOCl2 molecule? (Choose the
closest value.)
A
Li
B
B
A
60
C
Sc
B
90
D
V
C
109
E
Ni
D
120
E
180
What is the formula of the stable compound formed
by calcium and chlorine?
o
o
o
o
o
A
CaCl
B
Ca2Cl
C
Ca3Cl
A
VO
D
CaCl3
B
VO2
E
CaCl2
C
VO3
D
V2O3
E
V2O5
13 An oxide of vanadium is 48.5% oxygen by mass.
What is the empirical formula of this oxide?
10 What is the net ionic equation for the reaction that
occurs when aqueous solutions of HOCl, a weak acid,
and calcium hydroxide, Ca(OH)2, are combined?
A
2 HOCl(aq) + Ca(OH)2(aq)
14 When 0.100 kg of solid metal at 95.0 °C is placed into
0.300 kg of water at 25.0 °C, the final temperature of
the system is 27.4 °C. What is the identity of the
metal? Assume the system is thermally insulated
from its surroundings.
→ Ca(OCl)2(aq) + 2 H2O(l)
−
B
H (aq) + OH (aq) → H2O(l)
C
2 HOCl(aq) + Ca (aq) + 2 OH (aq)
+
−
2+
→ Ca(OCl)2(s) + 2 H2O(l)
−
−
D
HOCl(aq) + OH (aq) → OCl (aq) + H2O(l)
E
2 H (aq) + 2 OCl (aq) + Ca (aq) + 2 OH (aq)
+
−
2+
−
→ Ca(OCl)2(aq) + 2 H2O(l)
11 The volume of Earth’s oceans has been estimated to
9
3
be about 1 billion cubic kilometres (1×10 km ). About
how many water molecules are there in Earth’s
oceans? (Choose the closest answer.)
A
Fe(s)
B
Sn(s)
C
Mn(s)
D
Ti(s)
E
Pb(s)
15 Which of the following is not an ionic compound?
A
ammonium fluoride, NH4F
B
sodium hydroxide, NaOH
65
C
lithium nitrate, LiNO3
85
D
oxygen difluoride, OF2
E
potassium hydride, KH
35
A
10
B
10
C
10
D
10
E
10
45
100
For water:
3
d = 1 g/mL = 1000 kg/m
Molar mass, 18 g/mol
Specific heat
−1 −1
(in J °C g ):
H2O(l) 4.18
Mn(s)
0.479
Sn(s)
0.228
Fe(s)
0.445
Ti(s)
0.522
Pb(s)
0.130
© 2012 UNIVERSITY OF WATERLOO CHEM 13 NEWS EXAM / 3
16 Consider the following energy level diagram for a
reaction that occurs in a single step.
Potential
Energy
18 Which of the following substances are produced
when K2O is added to water?
Products
Reactants
Reaction progress
+
A
H2(g), K (aq) and O2(g) only
B
H2(g), K(s) and O2(g) only
C
K (aq) and H2O(l) only
D
K (aq) and OH (aq) only
E
K (aq), H2O(l) and O2(g) only
+
−
+
+
Which of the following statements is true?
−11
19 For the reaction below, Kc = 4.5×10
A
The activation energy for the reverse reaction is
less than zero.
B
Starting from reactants only, and before
equilibrium is established, the rate of the forward
reaction continually increases.
C
The effect of a temperature change on the rate is
greater for the forward reaction than for the
reverse reaction.
D
E
In an experiment, 1.0 mol each of A and C are placed
in an empty 1.0 L container and then the container is
o
sealed and heated to 500 C. Which of the following
statements is true?
The equilibrium concentrations of A and B will
−1
both be very close to 2 mol L .
B
The activation energy for the forward reaction is
less than that of the reverse reaction.
The equilibrium concentration of B will be much
−1
less than 1.0 mol L .
C
The equilibrium concentration of C will be slightly
−1
greater than 1.0 mol L .
The enthalpy change for the forward reaction is
less than zero.
D
The equilibrium concentration of C will be much
−1
greater than 1 mol L .
E
The reaction cannot reach equilibrium from the
specified initial conditions.
Step 1:
Step 2:

→ Q
←


→ P
Q ←

R
[R] = [Q] = [P]
C
[Q] = [P] / [R]
D
The rate of step Q → R is equal to the rate of
step Q → P.
−
20 The acetate ion, CH3COO , is the conjugate base of
−5
acetic acid, CH3COOH, a weak acid with Ka = 1.8×10
o
at 25 C. Which of the following statements about the
acetate ion is incorrect?
The rate of step R → Q is equal to the rate of
step Q → P.
B
E
 C(g)
A
17 Suppose that conversion of reactant R to product P
involves the following sequence of reversible
reactions. When the system reaches a state of
dynamic equilibrium, which of the following
statements is true?
A
A(g) + 2 B(g)
o
at 500 C.
The rate of step R → Q is equal to the rate of
step Q → R.
4 /CHEM 13 NEWS EXAM © 2012 UNIVERSITY OF WATERLOO
−
A
The H-C-H angles in the CH3COO ion are very
o
close to 109 .
B
The negative charge of the CH3COO ion is
shared equally by the two oxygen atoms.
C
The CH3COO ion is a strong base in water.
D
The O-C-O angle in the CH3COO ion is very
o
close to 120 .
E
The C-C-O angle in the CH3COO ion is very
o
close to 120 .
−
−
−
−
21 All but one of the following molecules are isomers.
Which one is not an isomer of the others?
23 In which of the following is the nitrogen-to-nitrogen
distance the greatest?
H2C
CH
A
the dinitrogen molecule, N2
H2C
CH
B
the linear azide ion, N3
C
the hydrazine molecule, N2H4
CH2
D
the diazene molecule, N2H2
C
E
the nitrous oxide molecule, NNO
A
B
H3C
−
CH3
24 In an experiment, the rate of the chemical reaction
between substances X and Y is found to obey the
following equation, where k is a constant.
HC
C
2
CH
rate = k [X] [Y]
CH3
What is the effect on the rate if, in a subsequent
experiment, the starting concentrations of X and Y are
each reduced by a factor of two?
HC
H3C
D
C
C
H2C
E
CH3
CH
CH
CH2
A
The rate increases by a factor of four.
B
The rate decreases by a factor of four.
C
The rate increases by a factor of eight.
D
The rate decreases by a factor of eight.
E
The rate decreases by a factor of two.
25 To determine the percentage by mass of chlorine in a
solid mixture of salts, what action should be
performed first?
22 Which of the following, in principle, spontaneously
oxidizes Zn(s) under standard conditions?
Half–Reaction
3+
−
2+
Fe (aq) + e  Fe (aq)
–
–
I2(s) + 2e  2 I (aq)
+
−
2+
−
2 H (aq) + 2e  H2(g)
Zn (aq) + 2e  Zn(s)
−
3+
Al (aq) + 3e  Al(s)
o
E
+0.77 V
A
Weigh the salt mixture.
B
Use an oxidizing agent to liberate the chlorine.
C
Add aqueous silver nitrate to the salt mixture.
D
Dissolve the salt mixture in water.
E
Use a reducing agent to liberate the chlorine.
+0.54 V
0.0 V
−0.76 V
–1.66 V
26 Which of the following has the largest radius?
A
H2(g)
A
Na
B
I2(s)
B
K
C
Al (aq)
C
Ca
D
Al(s)
D
Cl
E
2+
E
Br
3+
Fe (aq)
© 2012 UNIVERSITY OF WATERLOO CHEM 13 NEWS EXAM / 5
27 For a given substance, which of the following phase
transitions is the most exothermic?
31 Which of following has the smallest first ionization
energy?
A
solid → liquid
A
nitrogen, N
B
gas → liquid
B
fluorine, F
C
liquid → gas
C
silicon, Si
D
solid → gas
D
phosphorus, P
E
gas → solid
E
chlorine, Cl
32 Which statement about catalysts is incorrect?
28 A cylinder of unknown volume contains helium gas,
He(g), at 3.50 atm and 315 K. The helium gas is then
transferred to a 7.0 L gas cylinder containing Ne(g), at
2.50 atm and 315 K. If the final total pressure at
315 K is 5.75 atm, then what is the volume of the
cylinder that initially contained the helium gas?
(Choose the closest value.)
A
6.5 L
B
5.0 L
C
9.8 L
D
3.5 L
E
8.2 L
2−
T-shaped
B
tetrahedral
C
see-saw
D
square planar
E
octahedral
−12
3.99
B
3.68
C
7.03
D
10.01
E
10.38
B
A catalyst is not consumed by a reaction, though
it may be temporarily changed.
C
Catalysts, reactants, and products can be either a
homogeneous or heterogeneous system.
D
A catalyst decreases the enthalpy change of the
reaction it catalyzes.
E
A catalyst changes the reaction mechanism of the
reaction it catalyzes.
A
C2H2
B
SF6
C
NH3
D
BeF2
E
PF5
ion?
o
30 For Mg(OH)2, Ksp = 7.1×10 at 25 C. What is the pH
o
of a saturated solution of Mg(OH)2 at 25 C?
A
A catalyst speeds up both the forward and
reverse reactions.
33 Which of the following molecules has at least one
o
bond angle of 120 ?
29 What is the shape of the SO4
A
A
34 When the following equation is balanced and written
with the smallest whole number coefficients, what is
the coefficient of O2?
C5H10O5 + O2 → CO2 + H2O
6 /CHEM 13 NEWS EXAM © 2012 UNIVERSITY OF WATERLOO
A
2
B
3
C
5
D
6
E
none of the above
35 A 0.250 g sample of an unknown acid requires
−1
17.3 mL of 0.140 mol L NaOH(aq) for complete
neutralization. What is the molar mass of the acid?
Assume the acid has only one acidic hydrogen atom.
−1
A
69.2 g mol
B
137 g mol
C
14.5 g mol
D
242 g mol
E
−1
−1
B
N
C
N
D
N
N
−1
∆H ° = −393.5 kJ mol
2 C(s) + 3 H2(g) → C2H6(g),
∆H ° = −84.68 kJ mol
C2H6(g) +
103 g mol
N
∆H ° = −241.8 kJ mol
C(s) + O2(g) → CO2(g),
−1
N
−1
O2(g) → H2O(g),
1
2
H2(g) +
−1
Given the thermochemical equations above, what is
the standard enthalpy change for the reaction below?
The answers are expressed in kJ per mole of C2H6.
−1
36 Of the following structures, which one is the most
important structure for neutral N2O?
A
38 For the following reactions, the given enthalpy
changes are expressed per mole of product formed.
O
7
2
O2(g) → 2 CO2(g) + 3 H2O(g)
−1
A
−985.3 kJ mol
B
−1428 kJ mol
C
−720.0 kJ mol
D
−866.2 kJ mol
E
−550.6 kJ mol
O
−1
−1
−1
−1
O
3−
N
N
39 The ionization of H3PO4 to PO4 involves three
separate ionization reactions. The corresponding
ionization constants are Ka1, Ka2 and Ka3, respectively.
−1
In 1 mol L H3PO4(aq), the equilibrium concentration,
in moles per litre, of one of the species in solution is
approximately equal to Ka2. Which species has an
equilibrium concentration approximately equal to
−8
−1
6.2×10 mol L ?
O
O
E
N
N
37 Formic acid (HCOOH) is a weak monoprotic acid with
−4
Ka = 1.8×10 at 298 K. A solution is prepared by
dissolving 0.010 moles of HCOOH in water to make
1.0 L of solution at 298 K. Which of the following
actions, considered independently, causes an increase
in both the pH of the solution and the percentage
ionization of HCOOH?
(i) diluting with water to a final volume of 2.0 L
(ii) adding 0.004 moles of sodium formate, NaHCOO
(iii) adding 0.004 moles of HCl
A
(i) only
B
(ii) only
C
(iii) only
D
both (i) and (ii)
E
both (ii) and (iii)
+
A
H
B
H3PO4
C
H2PO4
D
HPO4
E
PO4
−
For H3PO4,
−3
Ka1 = 6.9×10
−8
Ka2 = 6.2×10
−13
Ka3 = 4.8×10
2−
3−
40 The strengths of acids are sometimes compared in
terms of their pKa values, where pKa = −log10 Ka.
Which of the following acids would have the largest
value for pKa?
A
hydrochloric acid, HCl(aq)
B
hydrobromic acid, HBr(aq)
C
hydroiodic acid, HI(aq)
D
hypochlorous acid, HOCl(aq)
E
hypobromous acid, HOBr(aq)
© 2012 UNIVERSITY OF WATERLOO CHEM 13 NEWS EXAM / 7
DATA SHEET
CHEM 13 NEWS EXAM
DETACH CAREFULLY
1
1A
1
H
1.008
3
Li
6.941
11
Na
22.99
19
K
39.10
37
Rb
85.47
55
Cs
132.9
87
Fr
(223)
2
2A
4
Be
9.012
12
Mg
24.31
20
Ca
40.08
38
Sr
87.62
56
Ba
137.3
88
Ra
226
3
4
3B
4B
21
22
Sc
Ti
44.96 47.88
39
40
Y
Zr
88.91 91.22
57-71
72
La-Lu
Hf
178.5
89-103 104
Ac-Lr
Rf
57
La
138.9
89
Ac
227.
58
Ce
140.1
90
Th
232.0
5
5B
23
V
50.94
41
Nb
92.91
73
Ta
180.9
105
Db
59
Pr
140.9
91
Pa
231.0
6
6B
24
Cr
52.00
42
Mo
95.94
74
W
183.9
106
Sg
60
Nd
144.2
92
U
238.0
7
7B
25
Mn
54.94
43
Tc
(98)
75
Re
186.2
107
Bh
61
Pm
(145)
93
Np
237.0
Constants:
NA =
R
6.022×10 mol−1
23
10
→
28
Ni
58.69
46
Pd
106.4
78
Pt
195.1
110
Ds
62
63
64
Sm
Eu
Gd
150.4 152.00 157.3
94
95
96
Pu
Am
Cm
(244) (243) (247)
11
1B
29
Cu
63.55
47
Ag
107.9
79
Au
197.0
111
Sg
65
Tb
158.9
97
Bk
(247)
12
2B
30
Zn
65.38
48
Cd
112.4
80
Hg
200.6
112
Cn
66
Dy
162.5
98
Cf
(251)
67
Ho
164.9
99
Es
(252)
68
Er
167.3
100
Fm
(257)
15
5A
7
N
14.01
15
P
30.97
33
As
74.92
51
Sb
121.8
83
Bi
209.0
69
Tm
168.9
101
Md
(258)
16
6A
8
O
16.00
16
S
32.07
34
Se
78.96
52
Te
127.6
84
Po
(209)
70
Yb
173.0
102
No
(259)
17
7A
9
F
19.00
17
Cl
35.45
35
Br
79.90
53
I
126.9
85
At
(210)
71
Lu
175.0
103
Lr
(260)
1 atm = 101.325 kPa = 760 torr = 760 mm Hg
−1
0.082058 atm L K
=
8.3145 kPa L K−1 mol−1
=
8.3145 J K−1 mol−1
−14
Kw =
1.0×10
F
96 485 C mol
Equations:
26
Fe
55.85
44
Ru
101.1
76
Os
190.2
108
Hs
9
8B
27
Co
58.93
45
Rh
102.9
77
Ir
192.2
109
Mt
14
4A
6
C
12.01
14
Si
28.09
32
Ge
72.59
50
Sn
118.7
82
Pb
207.2
Conversion factors:
=
=
8
←
13
3A
5
B
10.81
13
Al
26.98
31
Ga
69.72
49
In
114.8
81
Tl
204.4
−1
o
mol
0 C = 273.15 K
(at 298 K)
−1
PV = nRT
k t1/2 = 0.693
pH = pKa + log ( [base] / [acid] )
8 /CHEM 13 NEWS EXAM © 2012 UNIVERSITY OF WATERLOO
x=
−b ± b 2 − 4ac
2a
18
8A
2
He
4.003
10
Ne
20.18
18
Ar
39.95
36
Kr
83.80
54
Xe
131.3
86
Rn
(222)