As always, these are the…Real
AP Questions like those you’ll see in May…
equilibrium vapor
pressure at 20°C (torr)
75
44
92
0.06
substance
C6H6 (l)
C2H5OH (l)
CH3OH (l)
C2H6O2 (l)
1. Based on the data in the table above, which of the following liquid substances has the weakest
intermolecular forces?
(A) C6H6 (l)
(B) C2H5OH (l)
(C) CH3OH (l)
Ion
Zn+2
Ca+2
Ba+2
(D) C2H6O2 (l)
Ionic radius (pm)
74
100
135
2. Based on the data in the table above, which of the following correctly predicts the relative strength of the
attraction of Zn+2, Ca+2, and Ba+2 ions to water molecules in a solution, from strongest to weakest, and
provides the correct reason?
(A) Zn+2 > Ca+2 > Ba+2 because the smaller ions have a stronger coulombic attraction to water
(B) Zn+2 > Ca+2 > Ba+2 because the smaller ions are more electronegative
(C) Ba+2 > Ca+2 > Zn+2 because the larger ions are more polarizable
(D) Ba+2 > Ca+2 > Zn+2 because the larger ions are less electronegative
3. In the diagram to the right, which of the labeled arrows correctly identifies
hydrogen bonding in water?
(A) A
(B) B
(C) C
(D) D
4. The melting point of MgO is higher than that of NaF. Explanations for this
observation include which of the following?
I. Mg2+ is more positively charged than Na+
II. O2¯ is more negatively charged than F¯
III. The O2¯ ion is smaller than the F¯ ion
(A) II only
(B) I and II only
(C) I and III only
(D) II and III only
(E) I, II, and III
5. Which of the following actions would be likely to change the boiling point of a sample of a pure liquid in
an open container?
I. Placing it in a smaller container
II. Increasing the number of moles of the liquid in the container
III. Moving the container and liquid to a higher altitude
(A) I only
(B) II only
(C) III only
(D) II and III only
(E) I, II, and III
6. Consider the molecules represented above and the data in the table below.
Compound
nonane
2,3,4-trifluoropentane
Molecular formula
C9H20
C5H9F3
Molar Mass (g/mol)
128
126
Boiling point (°C)
151
89
Nonane and 2,3,4-trifluoropentane have almost identical molar masses, but nonane has a significantly
higher boiling point. Which of the following statements helps explain this observation?
(A) The C-F bond is easier to break than the C-H bond.
(B) The C-F bond if more polar than the C-H bond.
(C) The carbon chains are longer in nonane than they are in 2,3,4-trifluoropentane.
(D) The carbon chains are farther apart in a sample of nonane than they are in 2,3,4-trifluoropentane.
Use these answers for questions 7 - 10.
(A) hydrogen bonding
(B) hybridization
(C) ionic bonding
(D) resonance
(E) London dispersion forces
7. Is used to explain why iodine molecules are held together in the solid state
8. Is used to explain why the boiling point of HF is greater than the boiling point of HBr
9. Is used to explain the fact that the four bonds in methane are equivalent
10. Is used to explain the fact that the carbon-to-carbon bonds in benzene, C6H6, are identical
11. The cooling curve for a pure substance as it changes from a liquid to a
solid is shown right. The solid and the liquid coexist at
(A) point Q only
(B) point R only
(C) all points on the curve between Q and S
(D) all points on the curve between R and T
(E) no point on the curve
12. Give a scientific explanation for the following observations. Use
equations of diagrams if they are relevant.
(a) It takes longer to cook an egg until it is hard-boiled in Denver (altitude 1 mile above sea level) than it
does in New York City (near sea level).
(b) – (d) weren’t relevant to this chapter
13.
Substance
Melting Point, °C
H2
-129
C3H8
-190
HF
-92
CsI
621
LiF
870
SiC
>2,000
(a) Discuss how the trend in the melting points of the substances tabulated above can be explained in
terms of the types of attractive forces and/or bonds in these substances.
(b) For any pairs of substances that have the same kind(s) of attractive forces and/or bonds, discuss the
factors that cause variation in the strengths of the forces and/or bonds.
14. Using principles of chemical bonding and/or intermolecular forces, explain each of the following.
(a) Xenon has a higher boiling point than neon has.
(b) Solid copper is an excellent conductor of electricity, but solid copper chloride is not.
(c) SiO2 melts at a very high temperature, while CO2 is a gas at room temperature, event though Si and C
are in the same chemical family.
(d) Molecules of NF3 are polar, but those of BF3 are not.
…And the answers…
1.
2.
3.
4.
A
B
D
C
5.
6.
7.
8.
E
A
B
D
9. A
10. B
11. B
12. B
13.
14.
15.
16.
C
E
A
C
18. C
19. B
20. D
17. In Denver, pressure is lower (less air above to push down & fewer air mlcs in any volume) so there is less force
pushing down on the surface of the liquid…therefore, less force is required to make the molecules release from
the surface of the liquid…
21. a) H2 & C3H8 – London forces, weakest (H2 is lower because it has less mass and is, therefore, less
polarizable)…HF – hydrogen bonding, next weakest…CsI & LiF – ionic, next weakest (LiF is stronger
because its ions are smaller and hold more tightly together)…SiC – highest because it’s a covalent network
b) I think I just did that in (a)
22. a) both are London, so the deciding factor is the mass/# of electrons…Ne has more of each, so it’s more
polarizable
b) copper has delocalized e- running through it (as all metals do) but in CuCl2, the electrons are bound to the
positive and negative ions
c) two possible explanations here (don’t know exactly which is more important)…Si is more massive than C, so
SiO2 would have stronger London forces than CO2…SiO2 is sand/quartz and I think those are bonded
through a covalent network, though I’m not sure I could explain why that is
d) NF3 has a lone pair on the central atom – N…BF3 does not…NF3 is trigonal pyramidal, BF3 is trigonal
planar…NF3 is polar & has dipole-dipole forces…BF3 is nonpolar and has only weaker London forces…
23. a) like I can draw the thing on a computer…
b) the argon would sublime
c) the argon would change from liquid to gas – vaporize
d) liquid phase is less dense…line leans to the right, so compressing argon makes a solid
…And the answers…
1.
2.
3.
4.
A
B
D
C
5.
6.
7.
8.
E
A
B
D
9. A
10. B
11. B
12. B
13.
14.
15.
16.
C
E
A
C
18. C
19. B
20. D
17. In Denver, pressure is lower (less air above to push down & fewer air mlcs in any volume) so there is less force
pushing down on the surface of the liquid…therefore, less force is required to make the molecules release from
the surface of the liquid…
21. a) H2 & C3H8 – London forces, weakest (H2 is lower because it has less mass and is, therefore, less
polarizable)…HF – hydrogen bonding, next weakest…CsI & LiF – ionic, next weakest (LiF is stronger
because its ions are smaller and hold more tightly together)…SiC – highest because it’s a covalent network
b) I think I just did that in (a)
22. a) both are London, so the deciding factor is the mass/# of electrons…Ne has more of each, so it’s more
polarizable
b) copper has delocalized e- running through it (as all metals do) but in CuCl2, the electrons are bound to the
positive and negative ions
c) two possible explanations here (don’t know exactly which is more important)…Si is more massive than C, so
SiO2 would have stronger London forces than CO2…SiO2 is sand/quartz and I think those are bonded
through a covalent network, though I’m not sure I could explain why that is
d) NF3 has a lone pair on the central atom – N…BF3 does not…NF3 is trigonal pyramidal, BF3 is trigonal
planar…NF3 is polar & has dipole-dipole forces…BF3 is nonpolar and has only weaker London forces…
23. a) like I can draw the thing on a computer…
b) the argon would sublime
c) the argon would change from liquid to gas – vaporize
d) liquid phase is less dense…line leans to the right, so compressing argon makes a solid