CHEM 4A F2008 MT2 EXAM PRACTICE QUESTIONS
1) How many unpaired electrons are in O22+?
A) 0
B) 1
C) 2
D) 3
E) 4
C) 1.5
D) 2
E) 2.5
D) OF–
E) CO+
2) What is the bond order of NO?
A) 0.5
B) 1
3) Which of the following is not paramagnetic?
A) O2–1
B) OF
C) NO
For questions 4-8, choose the plot below that best demonstrates the relationship between the variables described
(assume variables not listed are constant).
A
C
B
B
D
4) Pressure vs. volume for an ideal gas.
A) A
B) B
C) C
D) D
E) E
D) D
E) E
5) Volume vs. temperature for an ideal gas.
A) A
B) B
C) C
6) Particle count (at each velocity) vs. the velocity of a gas.
A) A
B) B
C) C
D) D
E) E
D) D
E) E
7) PV/RT vs. P for a fixed amount of ideal gas.
A) A
B) B
C) C
8) Kinetic energy of a mole of ideal gas vs. temperature.
A) A
B) B
C) C
D) D
E) E
E
9) Which atoms have the highest rms velocity at 300K?
A) He
B) Xe
C) Ne
D) Ar
E) all are the same
10) Which atoms have the highest average kinetic energy at 300K?
A) He
B) Xe
C) Ne
D) Ar
E) all are the same
11) What is the shape of the ONF molecule?
A)
B)
C)
D)
E)
Linear
Bent
Trigonal planar
Trigonal pyramid
Tetrahedral
12) What is the hybridization of sulfur in SF4?
A)
B)
C)
D)
E)
sp
sp2
sp3
dsp3
d2sp3
13) What will occur with an increase in temperature at constant pressure when starting from the point (T1, P1)
on the following phase diagram?
P
P3
P2
P1
T1
A)
B)
C)
D)
E)
T2
T3
T
Solid to gas phase change.
Solid to liquid phase change.
Liquid to gas phase change.
Liquid to solid phase change
The system is a solid for all temperatures.
14) From bond enthalpies, which is the best estimate of the enthalpy of formation of ammonia from molecular
hydrogen and Nitrogen (kJ/ mol NH3)?
A) –99
B)
71
C) –41.5
D) –0.45
E)
499
15) How many isomers exist for the chlorinated hydrocarbon C4H9Cl?
A) 2
B) 4
C) 6
D) 8
E) 10
16) Which of the following molecules or ions is NOT linear?
A) ICl2
-
B) CO2
C) SO2
D) C2H2
E) HCN
17) In which of the molecules or ions below does nitrogen (N) have the highest oxidation state?
A) CN-
B) NO2
C) NO3-
E) NH4+
D) NH3
18) Which of the following compounds has an electric dipole moment?
A) CH4
B) BF3
C) XeF2
D) ClF3
E) CO2
-
19) Which of the following compounds is isoelectronic with CN ?
A) O2
B) N2
C) HCl
D) Br2
E) H2
20) Which of the following is a valid Lewis dot structure for hydrazine, N2H2?
A)
B)
C)
D)
E)
21) In which of the molecules or ions do all the atoms lie in the same plane?
A) CCl4
B) XeF4
C) SF4
D) FeCl4
-
E) TiCl4
22) Consider the formation of hydrogen peroxide from the elements in their standard states:
H2 + O2  H2 O2
How does the oxidation number of oxygen change in the above reaction?
A) -2  -2
B) -1  0
C) 0  0
D) 0  -1
E) 0  -2
23) The empirical formula of a hydrocarbon gas is CH2. If 2.10 g of gas occupies 1.12 L at 1.00 atm and 273 K,
what is the molecular formula of the hydrocarbon gas?
A) CH
B) CH2
C) C2H4
D) C3H6
E) C4H8
24) Which of the following molecules has a nonzero dipole moment?
A) CH3
+
B) BF3
C) AlBr3
D) PCl3
E) CO2
-
25) Which of the following molecules has a molecular geometry most similar to SF42 ?
A) CCl4
B) NH4+
C) BF4
-
D) SI4
E) XeF4
26) Three Lewis structures of carbonyl sulfide are shown. Fill in the boxes for formal charge on each atom and
explain which is the best structure in 20 words or less.
O
Formal Charge
Explanation:
C
S
O
C
S
O
C
S
For the following molecules, draw the best Lewis structure showing all bonds and lone pairs of electrons
(include resonance if needed).
N3 -
Complete the following table based on the Lewis structures.
Polar?
(yes/no)
Electronic Structure about the
central atom
Molecular Structure
Hybridization of the central
atom
COCl2 (C is the central atom)
Acrylonitrile is an important building block for synthetic fiber. It can be made by the reaction of propane with
ammonia and oxygen, as follows:
C3H6 (g) + NH3 (g) + O2 (g) → C3H3N (l) + 6 H2O (l)
a) Draw the Lewis Dot Structure of the reactant propane C3H6 and indicate the geometry (trigonal, linear
etc.) of each of the “C” atoms.
Geometry
Lewis Dot Structure:
C (1)
C (2)
C (3)
b) What mass of Acrylonitrile is formed by the reaction of 2.0 moles of propane and 2.0 moles of ammonia
(NH3) in the presence of excess oxygen.
c) Compare the oxygen-oxygen bond order and bond angle for O2 and O3 by completing the table below.
Ozone
Bond Angle
Bond Order
Molecular oxygen
Consider the dissociation of molecular chlorine (Cl2) to atomic chlorine (Cl):
Cl2 → 2 Cl
a) The bond enthalpy of the Cl-Cl bond is 242 kJ / mol. What is the minimum wavelength (λ, in nm) of light
required to break the bond?
b) Using ↑ and ↓, fill in the corresponding electronic orbital diagrams for Cl2 and Cl.
Cl2:
3pπ*
3pσ
*
3pπ
Cl:
3pπ*
3p
3pπ
3s
3pσ
3sσ*
3sσ
c) What is the change in paramagnetism for the Cl2 dissociation reaction. Circle your answer.
Increases
Decreases
Stays the same