Download AVOGADRO EXAM 2013 - Answers

AVOGADRO EXAM 2013 - Answers
1 An ion having 18 electrons, 15 protons and 16
neutrons has a mass number of?
In which region of the periodic table would you find the
elements of highest electronegativity?
49
A
B
34
*B upper right
C
33
C
middle
*D 31
D
bottom left
17
E
bottom right
Which of the following elements has the
greatest density at 25 oC and 101 kPa?
A
cesium, Cs
B
radon, Rn
6
*C lead, Pb
3
D
carbon, C
E
iron, Fe
Compared to an electron, a neutron has
A
Which of the following most correctly represents the
reaction between hydrochloric acid and water?
A
HCl + H2O → H2 + HOCl
B
HCl + H2O → 2 H+ + OH− + Cl−
*C HCl + H2O → H3O+ + Cl−
7
the same charge and about the same mass
D
HCl + H2O → 3 H+ + O2− + Cl−
E
HCl + H2O → 3 H+ + OCl−
Common table sugar is a compound with the formula
C12H22O11. How many oxygen atoms are present in one
mole of C12H22O11?
A
*B no charge and a much greater mass
4
upper left
A
E
2
5
6.02×1023
C
the opposite charge and much less mass
*B 6.62×1024
D
no charge and much less mass
C
5.46×1022
E
the opposite charge and a much greater mass
D
1.32×1025
E
7.22×1023
To which of the following elements does the term
metalloid apply most fittingly?
A
hydrogen
B
lithium
C
beryllium
8
*D boron
E
mercury
2 / AVOGADRO EXAM © 2013 UNIVERSITY OF WATERLOO
Which measurement is the most uncertain?
*A 0.10 ± 0.01 g
B
2.00 ± 0.05 L
C
1.00 ± 0.01 mm
D
0.200 ± 0.001 mL
E
1.000 ± 0.001 kg
9
12 According to the following equation, how many moles
of CO2 can be produced from 10.0 g Fe2O3 and
excess CO?
A compound is 53% carbon and 47% oxygen by
mass. What is the empirical formula of the
compound?
A
CO2
B
CO
A
C
C2O3
*B 0.0209 moles
3 Fe2O3 + CO → 2 Fe3O4 + CO2
*D C3O2
E
C53O47
10 A one litre sample of nitrogen gas is compared to a
one litre sample of hydrogen gas, both at 25 oC and
101 kPa. Which of the following statements is true?
A
Nitrogen and hydrogen molecules have the same
average speed.
*B On average, nitrogen molecules move more
slowly than the hydrogen molecules do.
C
3.33 moles
C
0.918 moles
D
1.00 moles
E
0.357 moles
13 Which of the following is a weak electrolyte in water?
A
HNO3
B
KOH
*C HF
Hydrogen molecules have a greater average
kinetic energy than the nitrogen molecules do.
D
On average, hydrogen molecules hit the walls of
the container with more force than the nitrogen
molecules do.
E
On average, nitrogen molecules hit the walls of
the container with more force than the hydrogen
molecules do.
11 What is the correct electron arrangement for an
arsenic (As) atom? (The first number in each list
refers to the number of electrons in the first shell; the
second number refers to the number of electrons in
the second shell; and so on.)
D
HBr
E
NH4F
14 What is the minimum volume of 6.00 mol L−1 H2SO4(aq)
required to neutralize 2.00 L of 2.25 mol L−1 NaOH(aq)?
2 NaOH(aq) + H2SO4(aq) → Na2SO4(aq) + 2 H2O(l)
*A 0.375 L
B
0.667 L
C
0.750 L
D
1.50 L
E
6.75 L
*A 2, 8, 18, 5
15 Which ion does not have the same shape as CH4?
B
10, 10, 3
C
2, 8, 2, 8, 2, 8, 2, 1
A
NH4+
D
2, 6, 10, 14, 1
B
BF4−
C
SO42−
E
8, 8, 8, 8, 1
*D PF4−
E
BrO4−
© 2013 UNIVERSITY OF WATERLOO AVOGADRO EXAM / 3
16 An element occurring in nature as a metal, such as
silver or gold, is likely to
A
react readily with oxygen to form a
protective coating
B
be at the high end of the activity series of metals
C
react readily with strong acids to release
hydrogen gas
D
lose some of its valence electrons easily
20 The following sequence of reactions is used in the
preparation of sodium sulfate, Na2SO4.What is the
minimum amount of O2 required to make 1.0 mole
of Na2SO4?
S + O2 → SO2
2 SO2 + O2 → 2 SO3
SO3 + H2O → H2SO4
2 NaOH + H2SO4 → Na2SO4 + 2 H2O
*E undergo oxidation only with difficulty
17 Which of the following involves a chemical change?
A
D
sublimation
E
vaporization
B
0.50 moles
C
1.0 mole
E
*B electrolysis
distillation
0.33 moles
*D 1.5 moles
crystallization
C
A
2.0 moles
21 The chemical equation representing the decomposition
of nitroglycerine, C3H5(NO3)3, is given below.
4 C3H5(NO3)3(s) → 12 CO2(g) + 6 N2(g) + O2(g) + 10 H2O(g)
What is the total volume of gas produced at 100 oC and
2 atm from 454 grams of nitroglycerine?
18 When a sample of sugar, C12H22O11, is treated with
concentrated H2SO4, a black product (carbon) is
obtained. The action of concentrated H2SO4 on sugar
illustrates the fact that H2SO4 is
*A a powerful dehydrating agent
A
89.6 L
B
111 L
C
162 L
B
highly unstable
*D 222 L
C
a strong acid
E
D
a strong oxidizing agent
E
a strong reducing agent
22 Consider the following unbalanced equation. (This
question can be answered without balancing the
equation.)
19 What is the oxidation state of chlorine in NaClO3?
A
+4
B
+3
*C +5
D
−2
E
−1
444 L
4 / AVOGADRO EXAM © 2013 UNIVERSITY OF WATERLOO
As2S5 + HNO3 → H3AsO4 + H2SO4 + NO2
Which of the following statements is true?
A
As of As2S5 is oxidized.
*B N of HNO3 is reduced.
C
S of As2S5 is reduced.
D
As of As2S5 is reduced.
E
As2S5 is acting as an oxidizing agent.
27 A 0.480 L sample of “wet” hydrogen gas was
collected over water at a barometric pressure of
735.4 Torr and a temperature of 21.7 oC. The
vapour pressure of water at this temperature is
19.498 Torr. What is the volume of the “dry”
hydrogen gas at STP?
23 If an element X forms the following stable
compounds and ions, what is element X?
CX2
NX3−
CaX
SX32−
A
beryllium, Be
B
carbon, C
*A 0.419 L
C
fluorine, F
B
0.468 L
C
0.488 L
D
0.522 L
E
22.4 L
*D oxygen, O
E
hydrogen, H
24 Which of the following statements is not correct?
A
The first ionization energy generally decreases
from top to bottom within a group.
B
The atomic radius generally increases from top to
bottom within a group.
*C The first ionization energy generally decreases
from left to right across a period.
28 What mass of impure solid KOH is needed to make
up 1.20 L of 0.60 mol L−1 KOH(aq)? Assume the
impure KOH is 84% KOH by mass and 16% water.
A
34.2 g
B
40.4 g
*C 48.1 g
D
The second ionization energy of an atom is
always greater than the first ionization energy.
D
87.0 g
E
The atomic radius generally decreases from left to
right across a period.
E
112 g
25 Which of the following atoms has more than two
unpaired electrons in its ground electronic state?
29 In an experiment, 4 drops of 0.100 mol L−1 CuSO4(aq)
were added to 150.0 mL of (NH4)2S2O8 solution. What
is the resulting concentration of CuSO4? Assume that
20 drops is equivalent to 1 mL.
A
germanium, Ge
A
1.67×10−4 mol L−1
B
selenium, Se
B
6.67×10−4 mol L−1
C
scandium, Sc
C
5.32×10−4 mol L-1
D
nickel, Ni
D
2.67×10−3 mol L−1
*E iron, Fe
26 Which of the following molecules has the shortest
carbon-carbon bond?
A
CH3CH3
B
CH2CH2
*C C2H2
760 Torr = 1 atm
STP = 1 atm and 0 oC
*E 1.33×10−4 mol L−1
30 For a chemical reaction, the limiting reactant is the one
that is
A
least stable
B
most stable
C
most expensive
still present after the reaction is complete
D
CH3COOH
D
E
CH3CH2OH
*E completely used up
© 2013 UNIVERSITY OF WATERLOO AVOGADRO EXAM / 5
31 During the process K(g) → K+(g) + e−
A
energy is released and the ion is larger
than the atom
B
energy is absorbed and the ion is larger
than the atom
C
energy is released but the atom and the ion
have the same size
35 The pH of an aqueous solution at 25 oC is 9.83.
What is the hydrogen ion concentration, [H+]?
energy is released and the ion is smaller
than the atom
9.8 mol L−1
B
0.99 mol L−1
C
2.28 mol L−1
*D 1.5×10−10 mol L−1
*D energy is absorbed and the ion is smaller
than the atom
E
A
E
5.4×10−5 mol L−1
36 What is the minimum volume of O2 needed to burn
completely 15.0 L CH4 at standard temperature and
pressure?
32 In the phrase “like dissolves like”, to what does the
word “like” refer?
A
15.0 L
7.50 L
A
densities
B
B
molar masses
*C 30.0 L
C
heats of formation
D
5.0 L
D
heats of solution
E
45.0 L
*E molecular polarities
33 Which of the following salt solutions will have a pH
nearest to 7 at 25 oC?
37 Which of the following compounds is ionic?
A
*A 0.1 mol L−1 NaNO3(aq)
H2O
*B BaF2
B
0.1 mol L−1 NH4Br(aq)
C
PF3
C
0.1 mol L−1 KHSO4(aq)
D
SiC
D
0.1 mol L−1 NaHCO3(aq)
E
SiF4
E
0.1 mol L−1 Na2CO3(aq)
34 When 0.483 grams of a compound is vapourized, its
volume is 0.358 L at 180 oC and 84.7 kPa. What is
the molar mass of the compound?
38 Which of the following has no lone pairs on the
underlined atom?
A
OF2
H2S
A
23.8 g mol−1
B
B
731 g mol−1
*C NH4+
C
14.3 g mol−1
D
H3O+
D
40.0 g mol−1
E
HOF
*E 60.0 g mol−1
6 / AVOGADRO EXAM © 2013 UNIVERSITY OF WATERLOO
39 A mixture of Fe2O3 and CuO weighing 1.000 g is
reduced in a stream of hot hydrogen gas. The
resulting mixture of metallic iron and metallic copper
weighs 0.721 g. What was the percentage by mass of
Fe2O3 in the original mixture?
A
21.7%
B
48.1%
C
69.3%
D
72.1%
Molar masses
(in g mol1):
O, 16.0
Fe, 55.85
Cu, 63.55
Fe2O3, 159.7
CuO, 79.55
*E 78.3%
40 For the reaction A → products, the concentration of
A decreases by a factor of two every 32 minutes. If
the initial concentration of A is 1.0 mol L−1, what is
the concentration of A after 48 minutes?
A
0.33 mol L−1
*B 0.35 mol L−1
C
0.38 mol L−1
D
0.44 mol L
E
0.25 mol L−1
© 2013 UNIVERSITY OF WATERLOO AVOGADRO EXAM / 7