Practice Exam 4 –
Chapters 8, 10, 11
Multiple Choice (3
points each)
_____1. Which compound has the largest (most negative) lattice energy?
A) CaO
B) MgO
C) CaS
D) MgS
_____2. What is the formal charge on chlorine if the compound has this
Lewis structure?
A) 0 F) -3 B) +3 G) -5 C) +5 H) -7 D) +7 I) -4 E) + 4
_____3. How do the magnitudes of the H-N-H bond angles vary in these species?
A) NH2-
< NH3 < NH4+
B) NH2- < NH4+ < NH3
C) NH3 < NH2- < NH4+
D) NH3 < NH4+ < NH2-
_____4.Which molecule has the greatest bond energy?
A) CO B) O2 C) NO D) F2
_____5. The bonds in ozone, O3, are best represented as
A) distinct single and double bonds
B) a single and a double bond that switch positions rapidly
C) something between a single and a double bond
D) two double bonds
_____6. Select the most polar bond.
A) C-O B) Si-F C) Cl-F D) C-F E) F-F
_____7. When these substances are arranged in order of increasing boiling point (lowest boiling point first), what is the correct order?
A) NH3 < PH3 < AsH3
B) AsH3 < PH3 < NH3
C) PH3 < AsH3 < NH3
D) AsH3 < NH3 < PH3
_____8. Analysis of an unknown substance showed that it has a high boiling point and is brittle. It insulates as a solid but conducts electricity when melted. This could be
A) HCl B) Al C) KBr D) SiF4
_____9. The pressure on a sample of water at its triple point is reduced while the temperature is held constant. Which phase change(s) are favored?
II. sublimation
III. vaporization
A) I only
B) III only
C) I and II only
D) II and III only
_____10. If a solute dissolves in an endothermic process,
A) H bonds must exist between the solvent and the solute.
B) strong ion-dipole forces must exist in the solution.
C) the entropy of the solution must be greater than that of its pure components.
D) the process gives off heat.
11. (6 pts) Consider the related species, CO and CO2.
A) Draw Lewis structures for each.
B) Compare the C-O bond lengths expected for each species and explain your reasoning.
12. (4 pts) Draw molecular distribution vs. kinetic energy for a liquid at two temperatures and use it to explain why vapor pressure increases with temperature.
13. (10 pts) For each of the following substances, circle the one intermolecular force which would predominate in the solid or the liquid.
Substance
C2H6 Ionic Dipole- H
Dipole Bonding Dispersion
Al2O3 Ionic Dipole- H
Dipole Bonding Dispersion
CH3OH Ionic Dipole- H
Dipole Bonding Dispersion
F2 Ionic Dipole- H
Dipole Bonding Dispersion
CH3F Ionic Dipole- H
Dipole Bonding Dispersion
14. (8 pts) Draw a phase diagram for sulfur dioxide, SO2 given the following data:
normal melting point = -72.7 oC
normal boiling point = -10 oC
triple point = -75 oC at 10 torr
A) Plot Pressure on the vertical axis and temperature on the horizontal axis. Label the normal melting point, the normal boiling point, the triple point, and the predominate phase (s. l. or g) in each region of the diagram.
B) What change in state occurs when SO2 at -25 oC and 5 torr has its pressure increased to 760 torr at -25 oC?
__________________________
15. (16 pts) Draw Lewis Structures for the following species. Use formal charge to draw the best structure. Show resonance forms if needed.
A) ONCl (this is the order the atoms are bonded)
B) IF3
C) XeOF2 (all atoms bonded to Xe)
D) NO2- ion
E) Complete the following table:
|
Species |
VSEPR Shape (Geometry) |
Molecular Shape (Geometry) |
|
ONCl |
|
|
|
IF3 |
|
|
|
XeO2F2 |
|
|
|
NO2- |
|
|
