Download avogadro exam 2004 - University of Waterloo

AVOGADRO EXAM 2004
UNIVERSITY OF WATERLOO
DEPARTMENT OF CHEMISTRY
20 MAY 2004
TIME: 75 MINUTES
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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
3
4
24.31
3B
4B
20
21
22
Ca
Sc
Ti
40.08
44.96 47.88
38
39
40
Sr
Y
Zr
87.62
88.91 91.22
56
(57-71)
72
Ba
La-Lu
Hf
137.3
178.5
88
(89-103) 104
Ra
Ac-Lr
Rf
(226)
5
5B
23
V
50.94
41
Nb
92.91
73
Ta
180.9
105
Db
6
6B
24
Cr
52.00
42
Mo
95.94
74
W
183.9
106
Sg
7
7B
25
Mn
54.94
43
Tc
(98)
75
Re
186.2
107
Bh
8
←
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
10
→
28
Ni
58.69
46
Pd
106.4
78
Pt
195.1
110
Uun
11
1B
29
Cu
63.55
47
Ag
107.9
79
Au
197.0
111
Uuu
12
2B
30
Zn
65.38
48
Cd
112.4
80
Hg
200.6
112
Uub
13
3A
5
B
10.81
13
Al
26.98
31
Ga
69.72
49
In
114.8
81
Tl
204.4
113
Uut
14
4A
6
C
12.01
14
Si
28.09
32
Ge
72.59
50
Sn
118.7
82
Pb
207.2
15
5A
7
N
14.01
15
P
30.97
33
As
74.92
51
Sb
121.8
83
Bi
209.0
16
6A
8
O
16.00
16
S
32.07
34
Se
78.96
52
Te
127.6
84
Po
(209)
17
7A
9
F
19.00
17
Cl
35.45
35
Br
79.90
53
I
126.9
85
At
(210)
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)
AVOGADRO EXAM 2004 - ANSWERS
1
How many neutrons, protons and electrons are there
in one 25Mg+ ion?
A
25 neutrons, 25 protons, 24 electrons
-
-
2-
-
2-
A
X (g) + e → X (g)
12 neutrons, 13 protons, 12 electrons
C
13 neutrons, 12 protons, 13 electrons
B
X(g) + 2e → X (g)
*D 13 neutrons, 12 protons, 11 electrons
C
X
D
X(g) → X
25 neutrons, 12 protons, 11 electrons
An element, Z, has only two isotopes, with relative
masses of 80.01 and 83.02. A naturally occurring
sample of this element has a relative mass of 81.82.
What is the percentage abundance of the lighter
isotope?
2+
(g) → X
+
*E X (g)
5
2+
→ X
3+
(g) + e
(g) + 2e
2+
-
-
(g) + e
-
What is the correct Lewis symbol for the oxygen atom?
A
O
B
O
C
O
What is the correct burette reading?
* D
O
24
E
O
A
30%
*B 40%
3
For which of the following processes is the energy
change equal to the second ionization energy of
X(g)?
B
E
2
4
C
50%
D
60%
E
70%
A
24.4 mL
B
24.52 mL
6
*C 24.47 mL
D
25.52 mL
E
24.5 mL
Which ion of magnesium is stable in magnesium
compounds?
*A Mg2+
25
B
Mg4+
C
Mg3+
D
Mg+
E
Mg
-
 2004 UNIVERSITY OF WATERLOO AVOGADRO EXAM /2
7
A
3.2×10-23 g
B
1.9×10-25 g
C
5.2×10-26 g
A
iron ions
*B calcium ions
C
sodium ions
2.7×10-26 g
D
chloride ions
E
fluoride ions
Which of the following bonds has the least ionic
character?
*A H-C
9
Avogadro constant:
NA = 6.022×1023 mol-1
*D 5.3×10-23 g
E
8
11 Which one of the following is the major cause of
hardness in natural groundwater?
What is the mass of one oxygen molecule?
B
O-H
C
K-H
D
C-F
E
C-O
12 The reaction
Electronegativity
values
H,
C,
O,
F,
K,
Br,
2 Na(s) + O2(g) → Na2O2(s)
2.1
2.5
3.5
4.0
0.8
2.8
is an example of
*A a synthesis reaction
In what region of the periodic table are the least
metallic elements found?
A
upper centre
B
lower centre
*C upper right
D
lower left
E
upper left
B
a decomposition reaction
C
a single displacement reaction
D
a double displacement reaction
E
an addition reaction
IUPAC defines an addition reaction as “a chemical reaction of two or
more reacting molecular entities, resulting in a single reaction product
containing all atoms of all components, with formation of two chemical
bonds and a net reduction in bond multiplicity in at least one of the
reactants.” An example of an addition reaction is the addition of HBr
across the double bond of ethene.
13 When zinc metal is treated with dilute aqueous
sulfuric acid, H2SO4(aq), the products are
10 What is the correct formula for bismuth (III) sulfide?
A
Bi3S
B
BiS3
C
Bi3S2
*D Bi2S3
E
A
ZnSO4, O2 and H2O
B
Zn(OH)2 and SO3
C
Zn(OH)2 and SO2
*D ZnSO4 and H2
BiS
E
ZnS, H2O and O2
 2004 UNIVERSITY OF WATERLOO AVOGADRO EXAM /3
14 What are the spectator ions in the reaction below?
Pb(NO3)2(aq) + 2 KI(aq) → PbI2(s) + 2 KNO3(aq)
-
A
Pb2+, NO3 and I
B
Pb2+ and I
-
E
K+ and Pb2+
Pb
13.0%
*B 25.9%
-
2+
compound N2O5?
A
-
*C K+ and NO3
D
17 What is the percentage, by mass, of nitrogen in the
C
28.6%
D
35.0%
E
40.0%
+
and K
18 Which combination of solutions would produce a
15 Balance the equation below using the smallest whole
precipitate upon mixing?
number coefficients.
Cr2O3 +
KOH +
O2 →
K2CrO4 +
H2O
What is the coefficient of O2 when the equation is
balanced?
A
2
*B 3
C
4
D
6
E
8
A
Na2SO4(aq) and (NH4)2S(aq)
B
NaNO3(aq) and MgBr2(aq)
C
Ag2SO4(aq) and KNO3(aq)
*D CuSO4(aq) and BaCl2(aq)
E
(NH4)2CO3(aq) and KNO3(aq)
19 Consider the equation below.
16 A particular compound has the following mass
composition.
32.4% Na
0.71% H
21.8% P
45.1% O
What is the empirical formula of the compound?
A
NaH2PO3
B
Na2HPO3
C
Na2H3PO
D
NaH2PO4
*E Na2HPO4
2 NaOH + Cl2 → NaCl + NaClO + H2O
What is the maximum mass of NaClO that can be
obtained from a reaction mixture containing 50.0
grams of NaOH and 71 grams of Cl2?
*A 46.5 g
B
93.1 g
C
74.5 g
D
186 g
E
121 g
 2004 UNIVERSITY OF WATERLOO AVOGADRO EXAM /4
20 If 1.0 L of 0.10 mol L−1 NaNO3(aq) and 1.0 L of
0.20 mol L−1 Mg(NO3)2(aq) are mixed, what are the
final concentrations of Na+, Mg2+ and NO3 ?
A
-
-
[Na+] = 0.050 mol L 1, [Mg2+] = 0.10 mol L 1,
[ NO3 ] = 0.20 mol L 1
-
-
*B [Na+] = 0.050 mol L 1, [Mg2+] = 0.10 mol L 1,
[ NO3 ] = 0.25 mol L 1
C
D
E
-
*A ethyne, C2H2
B
hydrazine, N2H4
C
ethanol, C2H5OH
D
hydrogen fluoride, HF
E
water, H2O
-
[Na+] = 0.050 mol L 1, [Mg2+] = 0.20 mol L 1,
[ NO3 ] = 0.20 mol L 1
+
-1
2+
24 When three moles of calcium hydroxide, Ca(OH)2,
react completely with two moles of phosphoric acid,
H3PO4, how many moles of water are produced?
-1
[Na ] = 0.050 mol L , [Mg ] = 0.10 mol L ,
[ NO3 ] = 0.40 mol L 1
+
-1
2+
-1
[Na ] = 0.10 mol L , [Mg ] = 0.10 mol L ,
[ NO3 ] = 0.40 mol L 1
21 Which one of the following substances in aqueous
solution is a nonelectrolyte?
A
23 Which of the following does not show any significant
hydrogen bonding?
A
one
B
two
C
three
D
four
*E six
NH4Cl
*B CH3OH
C
LiF
D
HNO3
E
CO2
Note: CO2 produces
carbonic acid
(H2CO3) which
ionizes in solution.
22 Which of the following is the poorest electrical
conductor?
A
aqueous sulfuric acid
B
graphite
*C solid anhydrous potassium nitrate
D
platinum
E
molten sodium bromide
25 What is the minimum volume of pure oxygen required
to burn 10.0 L of pure propane, C3H8, completely to
carbon dioxide and water? (Assume that the volumes
of oxygen and propane are measured at the same
pressure and temperature.)
A
10.0 L
B
20.0 L
C
30.0 L
D
40.0 L
*E 50.0 L
 2004 UNIVERSITY OF WATERLOO AVOGADRO EXAM /5
26 What volume of 0.142 mol L−1 HCl(aq) is required to
neutralize 40.0 mL of 0.0217 mol L−1 Ca(OH)2(aq)?
29 Which colour of light has the highest energy per
photon?
*A 12.2 mL
A
red
B
6.11 mL
B
orange
C
3.06 mL
C
yellow
D
76.4 mL
D
green
E
17.2 mL
*E violet
27 A sample of gas occupies a volume of 27 L at 20oC
and normal atmospheric pressure. What is the
volume at 250oC if the pressure remains constant?
A
340 L
B
2.2 L
30 Consider a sample comprised of 1.00 moles of an
ideal gas. Which graph correctly displays how the
product of pressure and volume changes with
temperature?
PV
0oC ≡ 273 K
*A
0
*C 48 L
D
15 L
E
32 L
0
T
0
T
0
T
0
T
0
T
PV
B
0
28 What volume of ozone, O3, will have nearly the same
number of molecules as 1.00 L of O2 gas, if both
volumes are measured at the same temperature and
pressure?
PV
C
0
A
22.4 L ozone
B
6.00 L ozone
C
1.50 L ozone
PV
D
*D 1.00 L ozone
E
0
0.17 L ozone
PV
E
0
 2004 UNIVERSITY OF WATERLOO AVOGADRO EXAM /6
34 How many structural isomers of C4H8 are there?
31 What is the oxidation state of chlorine in Cl2O?
A
-2
B
-1
C
0
two
B
three
C
four
D
five
*E six
*D +1
E
A
+2
35 Which of the following electron attachment processes
is/are endothermic?
32 Use the bond dissociation enthalpies provided to
calculate ∆H for the reaction below.
3 H2(g) + N2(g) → 2 NH3(g)
What is ∆H for the reaction?
A
+122 kJ
*B -83 kJ
H-H
H-N
N−N
N=N
N≡N
-1
435 kJ mol
389 kJ mol 1
163 kJ mol 1
418 kJ mol 1
946 kJ mol 1
A
-
-
-
-
(1)
Na(g) + e → Na (g)
(2)
Mg(g) + e → Mg (g)
(3)
Cl(g) + e → Cl (g)
(4)
Ar(g) + e → Ar (g)
-
-
-
-
(1) and (2) only
C
-122 kJ
D
-1084 kJ
C
(4) only
E
-1770 kJ
D
(1), (2) and (3) only
E
(1), (2) and (4) only
33 Which of the following elements has the highest
boiling point?
*B (2) and (4) only
36 Exactly 10.0 g H2O(s) at 0oC is placed on top of
0.100 kg Cu(s) at 100oC. What is the final
temperature of the combined system (water plus
copper), if no heat is lost to the surroundings?
N2
*A 6.9oC
B
F2
B
43oC
C
Cl2
C
21oC
D
Br2
D
35oC
E
65oC
A
*E I2
Energy is always released
when an electron is added
to a main group atom,
except when an electron is
added to a group 2 or 18
atom. Atoms in group 2
have completely filled
subshells (s2) and atoms of
group 18 have completely
filled shells.
Heat capacity of
Cu(s) is 0.39 J g-1 oC 1
The heat of fusion of
ice is 334 J g 1.
Heat capacity of
H2O(l) is 4.18 J g-1 oC 1
 2004 UNIVERSITY OF WATERLOO AVOGADRO EXAM /7
37 When 5.0-g of an impure sample of CaCl2 was treated
with excess AgNO3(aq), 0.50 g of dry AgCl was
obtained. What is the mass percentage of CaCl2 in
the impure sample?
A
40 What is the ratio x:y when the equation below is
properly balanced?
-
15%
CaCl2, 110.98 g mol 1
AgCl,
143.35 g mol
-1
x Sn2+(aq) + y Ag+(aq) → n Sn4+(aq) + m Ag(s)?
A
1:1
B
2:1
B
10%
C
7.7%
*C 1:2
D
5.0%
D
3:4
*E 3.9%
E
4:3
38 What is the H-N-H bond angle in ammonia, NH3?
(Choose the closest value.)
A
72o
B
90o
*C 109o
D
120o
E
180o
39 Which of the following is the correct Lewis (i.e.,
electron dot) structure for the N2O molecule?
A
N
N
O
B
N
N
O
C
N
N
O
Of the choices provided, only D
has the correct number of
valence electrons (16) and
gives each atom an octet.
*D
N
N
O
The “true” structure of N2O is a
resonance hybrid of at least
three resonance structures.
E
N
N
O
 2004 UNIVERSITY OF WATERLOO AVOGADRO EXAM /8