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# c120 sample exam questions fall 2020 - Solutions

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```CHEM 120 Sample Final Exam Questions
1.
page 1 of 22
Maprotiline is a prescription drug with the following mass composition:
86.59% C
8.36% H
5.05% N
What is the empirical formula of maprotiline?
2.
A.
C7H8N3
B.
C20H23N
C.
C87H8N5
D.
C3H3N
E.
C14H14N
What is the maximum mass of iron, Fe, that can be obtained from a reaction mixture
containing 2.5 g Al and 9.5 g Fe2O3 ? The balanced chemical equation for the reaction is
2 Al(s) + Fe2O3(s) → Al2O3(s) + 2 Fe(s).
A.
6.6 g
B.
10.4 g
C.
5.2 g
D.
1.7 g
E.
3.3 g
CHEM 120 Sample Final Exam Questions
3.
4.
page 2 of 22
A 1.85 g sample of a mixture of KCl and MgCl2 is treated with excess AgNO3(aq),
producing a white precipitate. If the precipitate weighs 3.82 g, then what is the
percentage by mass of KCl in the original mixture?
A.
36%
B.
54%
C.
75%
D.
87%
E.
93%
What volume of 0.19 mol L−1 HNO3(aq) is required to neutralize 15 mL of
0.38 mol L−1 Ca(OH)2(aq) ?
A.
7.5 mL
B.
15 mL
C.
30 mL
D.
45 mL
E.
60 mL
CHEM 120 Sample Final Exam Questions
5.
6.
7.
Which of the following combinations will produce a precipitate?
A.
NaOH(aq) plus HCl(aq)
B.
Ba(OH)2(aq) plus HNO3(aq)
C.
AgNO3(aq) plus HCl(aq)
D.
NH3(aq) plus HCl(aq)
E.
Fe(NO3)2(aq) plus KCl(aq)
What is the net ionic equation for the reaction of HCl(aq) with NaOH(aq)?
A.
H+(aq) + OH−(aq) → H2O(l)
B.
Na+(aq) + Cl−(aq) → NaCl(s)
C.
Cl−(aq) +
D.
HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
E.
HCl(aq) + NaOH(aq) → Na+(aq) + Cl−(aq) + H2O(l)
OH−(aq) → OCl−(aq) + H−(aq)
In which substance does iodine have an oxidation state of +3?
A.
HIO3
B.
IF5
C.
NaIO2
D.
HI
E.
I2
page 3 of 22
CHEM 120 Sample Final Exam Questions
8.
9.
page 4 of 22
Which of the following are oxidation-reduction reactions?
(i)
H2CO3(aq) → H2O(l) + CO2(g)
(ii)
2 Li(s) + 2 H2O(l) → 2 LiOH(aq) + H2(g)
(iii)
4 Ag(s) + PtCl4(aq) → 4 AgCl(s) + Pt(s)
(iv)
2 HClO4(aq) + Ca(OH)2(aq) → 2 H2O(l) + Ca(ClO4)2(aq)
A.
(i) and (iii)
B.
(ii) and (iii)
C.
(ii) and (iv)
D.
(iii) and (iv)
E.
(i), (ii), (iii) and (iv)
Oxalate ion, C2O42−, and permanganate ion, MnO4−, react in aqueous basic solution to
give carbonate ion, CO32−, and solid manganese dioxide, MnO2. The unbalanced
chemical equation is given below.
a C2O42−(aq) + b MnO4−(aq) + c OH − → x CO32−(aq) + y MnO2(s) + z H2O(l)
What is the ratio a:c when the equation is balanced?
A.
3:2
B.
2:3
C.
1:1
D.
3:4
E.
1:2
CHEM 120 Sample Final Exam Questions
10.
11.
page 5 of 22
The International Union of Pure and Applied Chemistry gives the atomic mass of carbon
as [12.0096,12.0116]. What is the justification for doing so?
A.
The isotopes of carbon are highly unstable.
B.
Measurements of the atomic mass by different methods yield different values.
C.
Carbon has only two isotopes, one with a mass of 12.0096 and the other with a
mass of 12.0116.
D.
The isotopic abundances of carbon vary from source to source.
E.
The mass of a carbon nucleus (no electrons) is 12.0096 and the mass of a carbon
atom (including electrons) is 12.0116.
An industrial process for the production of nitrosyl chloride, NOCl, is based on the
following reactions.
2 NH3 + 3 O2
⎯⎯
→
N2O3 + 3 H2O
N2O3 + 2 H2SO4
⎯⎯
→
2 HNOSO4 + H2O
HNOSO4 + HCl
⎯⎯
→
NOCl + H2SO4
What is the percent atom economy for the overall process? Choose the closest value.
A.
22%
B.
64%
C.
77%
D.
12%
E.
53%
CHEM 120 Sample Final Exam Questions
12.
page 6 of 22
Which of the following statement(s) is/are true?
(i)
When the electron of an H atom occupies the 1s orbital, there is zero probability of
finding the electron at a radial distance greater than 52.9 pm.
(ii)
When the electron of an H atom occupies the 2s orbital, the total energy, E, decreases
with the radial distance, r, between the electron and nucleus.
(iii) When the electron of an H atom occupies the 2py orbital, there is zero probability of
finding the electron in the xz plane.
13.
A.
(ii) and (iii)
B.
(i), (ii) and (iii)
C.
(i)
D.
(ii)
E.
(iii)
A graph of the radial probability distribution function, r2 R2, is shown below for an
orbital of the hydrogen atom. Which orbital could it be?
A.
2s
B.
3s
C.
3p
D.
3d
E.
4s
r2 R2
r
CHEM 120 Sample Final Exam Questions
14.
15.
16.
page 7 of 22
The radial factor for a hydrogen atom orbital is shown below. Which of the following
orbitals is depicted in the graph?
A.
3p
B.
5d
C.
2s
D.
3s
E.
4p
R
r
How many radial and angular nodes are there for a hydrogen-like 5dxy orbital?
A.
four radial nodes, zero angular nodes
B.
three radial nodes, two angular nodes
C.
two radial nodes, two angular nodes
D.
one radial node, two angular node
E.
one radial node, three angular nodes
For a xenon atom, Xe, in its ground electronic state, how many electrons have n = 3 ?
A.
six
B.
twelve
C.
fifteen
D.
eighteen
E.
thirty six
CHEM 120 Sample Final Exam Questions
17.
18.
19.
page 8 of 22
For an argon atom, Ar, in its ground electronic state, how many electrons have m = 0?
A.
two
B.
four
C.
six
D.
eight
E.
ten
Which one of the following atoms or ions is diamagnetic in its ground electronic state?
A.
Ti
B.
Ti2+
C.
C
D.
C2−
E.
Li−
What is the ground-state electron configuration of the V3+ ion ?
A.
[Ar] 3d 2
B.
[Ar] 4s 2
C.
[Ar] 4s 1 3d 1
D.
[Ar] 4s 2 3d 3
E.
[Ar] 4d 2
CHEM 120 Sample Final Exam Questions
20.
21.
22.
page 9 of 22
Which atom has the lowest first ionization energy?
A.
Be
B.
B
C.
C
D.
N
E.
O
Which of these atoms is pulled more strongly into an inhomogeneous magnetic field?
Assume each atom is in its ground electronic state.
A.
Li
B.
Be
C.
B
D.
C
E.
N
Select the ionic compound for which the cation and anion have the same ground state
electron configuration.
A.
NaCl
B.
KBr
C.
Li2O
D.
MgO
E.
MgS
CHEM 120 Sample Final Exam Questions
23.
24.
page 10 of 22
Based on the relative positions of H, C, N, O, P and S in the periodic table, which of the
following covalent bonds is the most polar ?
A.
H−C
B.
H−N
C.
H−O
D.
H−P
E.
H−S
For the sulfuric acid molecule (H2SO4), all four oxygen atoms are bonded to the central
sulfur atom and the two hydrogen atoms are bonded to different oxygen atoms. Several
resonance structures can be drawn for H2SO4 but, on the basis of formal charges, one
structure is more important than the others.
In the most important structure of H2SO4 , the sulfur atom has:
25.
A.
a formal charge of zero and a complete octet
B.
a formal charge of zero and an expanded octet
C.
a formal charge of +6 and an expanded octet
D.
a formal charge of +2 and a complete octet
E.
a formal charge of −2 and an expanded octet
Which of the following would be properly classified as a set of covalent molecules?
A.
MgCl2, ICl3, P4O10
B.
KBr, C2H6, SF4
C.
C6H6, NH4NO3, SO3
D.
CO, HOCN, O3
E.
K2O, HF, NH3
CHEM 120 Sample Final Exam Questions
26.
In which of the following does the nitrogen atom have a formal charge of −1?
A.
27.
28.
page 11 of 22
B.
C.
D.
E.
A possible Lewis structure for CH3NCO is shown below. What are the formal charges on
the nitrogen and oxygen atoms?
A.
zero on N, zero on O
B.
+1 on N, +1 on O
C.
−1 on N, −1 on O
D.
+1 on N, −1 on O
E.
−1 on N, +1 on O
H
H
C
N
C
O
H
Which of the following molecules or ions has a linear molecular geometry? The
underlined atom is the central atom.
A.
O3
B.
NO2−
C.
HN3
D.
XeF2
E.
ClO2+
CHEM 120 Sample Final Exam Questions
29.
30.
page 12 of 22
According to VSEPR theory, what is the molecular geometry of SeF4? (Se is the central atom.)
A.
see-saw
B.
trigonal pyramidal
C.
T-shaped
D.
tetrahedral
E.
square planar
Which of the following molecules has a permanent dipole moment?
A.
CF4
B.
SF4
C.
SO3
D.
all of the above
E.
none of the above
CHEM 120 Sample Final Exam Questions
31.
32.
33.
page 13 of 22
Which one of the following molecules is nonpolar? For each, the central atom is underlined.
A.
NH3
B.
CH2Cl2
C.
XeF4
D.
SO2
E.
H2 O
What is the maximum number of σ bonds that can be formed between two adjacent atoms
in a molecule?
A.
one
B.
two
C.
three
D.
four
Select the ending that makes the following a true statement.
According to valence bond theory, a  bond between two atoms could result from the
overlap of:
A.
two s orbitals
B.
an s orbital of one atom and a p orbital of the other atom
C.
an sp orbital of one atom and an sp orbital of the other atom
D.
a p orbital of one atom and a p orbital of the other atom
E.
an sp2 orbital of one atom and an sp2 orbital of the other atom
CHEM 120 Sample Final Exam Questions
34.
page 14 of 22
The following is an incomplete structure for the NH2CH2CHO molecule. Lone pairs are
not shown. Which statement concerning this molecule is true?
H
H
H
O
N
C
C
H
H
35.
A.
The hybridization of N is sp3.
B.
The H-N-H bond angle is 120o.
C.
There are nine  bonds in this molecule.
D.
The carbon atom that is bonded to O is sp3 hybridized.
E.
There are two  bonds in this molecule.
Draw the most important Lewis structure(s) for the NO3− ion. Which of the following
statements concerning the NO3− ion is correct? Note: The N atom is the central atom. All
three O atoms are bonded directly to the N atom.
A.
The bond angles are all 109o.
B.
Each nitrogen-oxygen bond has a bond order of 1.5.
C.
One of the nitrogen-oxygen bonds is shorter than the other two.
D.
The nitrogen atom has a formal charge of zero.
E.
The structure of the NO3− is best represented as a hybrid of three equivalent
resonance structures.
CHEM 120 Sample Final Exam Questions
page 15 of 22
Add bonds and/or lone pairs as appropriate to complete the skeleton structure below for the
H2CNNH2 molecule and then answer questions 42-45.
Hb
Ha
C
Hc
Nx
Ny
Hd
The letters “a”, “b”, “c”, “d”, “x” and “y” are used to identify the various H and/or N atoms.
36.
37.
38.
39.
What is the Ha-C-Hb angle? Choose the closest value.
A.
90o
B.
109o
C.
120o
D.
180o
What is the C-Nx-Ny angle? Choose the closest value.
A.
90o
B.
109o
C.
120o
D.
180o
What is the hybridization of Nx?
A.
sp
B.
sp2
C.
sp3
D.
sp3d
Which one of the following statements is true?
A.
There is only one π bond and it is between C and Nx.
B.
There is only one π bond and it is between Nx and Ny.
C.
There are two π bonds: one is between C and Nx and the other is between Nx and Ny.
D.
There are no π bonds.
CHEM 120 Sample Final Exam Questions
40.
41.
42.
page 16 of 22
Which of the following statements relating to molecular orbital (MO) theory is false?
A.
The combination of two atomic orbitals produces one bonding and one antibonding MO.
B.
A bonding MO is lower in energy than the two atomic orbitals from which it is formed.
C.
The combination of two 2p orbitals may result in either σ or π MOs.
D.
A homonuclear diatomic molecule with a bond order of zero will not be stable.
E.
A bonding MO cannot have any nodal planes.
According to molecular orbital theory, what is the ground state electron configuration for
the B2 molecule? The internuclear axis is defined as the z axis.
A.
(σ1s)2 (σ1s*)2 (σ2s)2 (σ2s*)2 (σ2pz)2
B.
(σ1s)2 (σ2s)2 (σ2p)2 (π2px)1 (π2py)1
C.
(σ1s)2 (σ2s)2 (π2px)2 (π2py)2 (π2pz)2
D.
(σ1s)2 (σ2s)2 (σ2px)2 (σ2py)2 (σ2pz)2
E.
(σ1s)2 (σ1s*)2 (σ2s)2 (σ2s*)2 (π2px)1 (π2py)1
Which of the following represents the σ2p* orbital? (0.5 marks)
A.
+
−
D.
+
+
B.
C.
E.
+
-
+
−
-
+
−
CHEM 120 Sample Final Exam Questions
43.
44.
page 17 of 22
Determine the bond orders for C2, C2+, and C2−. Which of the following series has these
species arranged from lowest to highest bond order?
A.
C2
C2+
C2−
B.
C2+
C2−
C2
C.
C2
C2−
C2+
D.
C2+
C2
C2−
E.
C2−
C2
C2+
Under what conditions of temperature and pressure are the deviations from ideal gas
behaviour least significant?
A.
high temperature and low pressure
B.
low temperature and high pressure
C.
low temperature and low pressure
D.
high temperature and high pressure
E.
gases always behave ideally
CHEM 120 Sample Final Exam Questions
45.
46.
page 18 of 22
Which of the following statements is correct?
A.
A gas will behave as an ideal gas when the distances between gas molecules
are small compared with the sizes of the molecules themselves.
B.
Hydrogen gas (2.0 g mol−1) effuses twice as fast as helium gas (4.0 g mol−1) at the
same temperature and pressure.
C.
The average speed of molecules in an ideal gas is directly proportional to the
kelvin temperature.
D.
In the Van der Waals equation, ( P + an 2 V 2 )(V − nb) = nRT , the parameter b
accounts for the strength of the intermolecular attractions.
E.
None of these statements are correct.
The molar volumes of C2H6(g) and H2(g), measured at 300 K and 10.0 atm, are observed
to be 2.30 L and 2.51 L, respectively. Which of the following statements accounts for the
observation that the molar volume of C2H6(g) is smaller than that of H2(g)?
A.
C2H6 molecules are larger than H2 molecules.
B.
The intermolecular attractions in C2H6(g) are weaker than they are in H2(g).
C.
The intermolecular attractions in C2H6(g) are stronger than they are in H2(g).
D.
The average kinetic energy of H2 molecules is greater than that of C2H6 molecules.
E.
The average kinetic energy of H2 molecules is less than that of C2H6 molecules.
CHEM 120 Sample Final Exam Questions
47.
page 19 of 22
Phosphine gas, PH3(g), oxidizes spontaneously on exposure to air. The chemical equation
for the reaction is given below. What volume of O2(g), measured at 101 kPa and 50 oC,
is consumed in the formation of 20.0 g of P2O3 by this reaction?
2 PH3(g) + 3 O2(g) → P2O3(s) + 3 H2O(g)
Molar masses:
(in g mol−1)
48.
A.
16.1 L
B.
14.5 L
C.
11.2 L
D.
8.15 L
E.
4.82 L
33.994
32.00
109.94
18.016
What is the maximum volume of C3H8 gas that can be obtained from 25.7 L of CO and
39.0 L of H2? Assume the volumes of all gases are measured at 713 oC and 1.15 atm.
Choose the closest value.
3 CO(g) + 7 H2(g)
A.
3.67 L
B.
13.0 L
C.
6.47 L
D.
5.57 L
E.
8.57 L
⎯⎯
→
C3H8(g) + 3 H2O(g)
CHEM 120 Sample Final Exam Questions
49.
50.
page 20 of 22
One of two identical balloons contained carbon dioxide (CO2) gas and the other
contained hydrogen (H2) gas. If it took 24 hours for all of the H2 to effuse out of its
balloon, how long did it take for all of the CO2 to effuse? (Choose the closest value.)
A.
530 hours
B.
1 hour
C.
110 hours
D.
5 hours
E.
230 hours
The boiling points of acetone (CH3COCH3) and butane (CH3CH2CH2CH3) are 56 oC and
−1.0 oC, respectively. Which of the following interactions contributes most to the
difference in boiling point of these two compounds?
A.
dipole-dipole forces
B.
London dispersion forces
C.
hydrogen bonding forces
D.
covalent bonding
E.
ionic bonding
CHEM 120 Sample Final Exam Questions
51.
52.
53.
page 21 of 22
Triethylamine, N(CH2CH3)3, is a liquid at 25 oC and 101 kPa. Which of the following
contribute to the attraction amongst molecules in liquid N(CH2CH3)3?
A.
dipole-dipole forces only
B.
London dispersion forces only
C.
hydrogen bonding forces only
D.
hydrogen bonding and London dispersion forces
E.
dipole-dipole and London dispersion forces
Which of the following substances has the lowest boiling point?
A.
CH3OH
B.
CH3CH2OH
C.
HCCH
D.
CCl4
E.
H2O
Which of the following has the lowest boiling point?
A.
HCl
B.
HI
C.
HF
D.
HBr
E.
HOI
CHEM 120 Sample Final Exam Questions
page 22 of 22
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