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AP Chemistry: Unit 10: Intermolecular Forces & Solution Chemistry: AP Practice Packet
1. A solution is made by dissolving 250.0g of potassium chromate crystals (K2CrO4, molar mass
194.2g/mol) in 1.00 kg of water. What will the freezing point of the new solution be? Kf for water is
1.86°C/m.
a. -8.87°C
b. -7.18°C
c. -5.73°C
d. -3.2°C
e. -1.86°C
2. Which of the following explains why CH3-O-CH3 has a lower boiling temperature than CH3CH2OH?
a. Hydrogen bonding
b. Hybridization
c. Ionic bonding
d. Resonance
e. London dispersion forces
3. Which of the following explains why, at room temperature, I2 is a solid and Br2 is a liquid?
a. Hydrogen bonding
b. Hybridization
c. Ionic bonding
d. Resonance
e. London dispersion forces
4. Which of the following is most likely to be a solid at room temperature?
a. HF
b. NH3
c. K2S
d. N2
e. H2O
5. Which of these explains that the C – C bonds in benzene are all the same length?
a. Hydrogen bonding
b. Hybridization
c. Ionic bonding
d. Resonance
e. London dispersion forces
6. 1-propanol, CH3CH2CH2OH, boils at 97°C and ethyl methyl ether, CH3CH2OCH3, boils at 7°C, although
each compound has identical chemical composition. The difference that is responsible for higher boiling
temperature is
a. Molar mass
b. Hydrogen bonding
c. Density
d. Specific heat
e. Enthalpy
7. Which of the following is true at the triple point of a pure substance?
a. The temperature is equal to the normal melting point.
b. All three states have identical densities.
c. The solid-liquid equilibrium will always have a positive slope moving upward from the triple
point.
d. The vapor pressure of the solid phase always equals the vapor pressure of the liquid phase.
e. The pressure is exactly one half of the critical pressure.
8. The critical temperature of a substance is the
a. Temperature at which the vapor pressure of the liquid equals the normal atmospheric pressure.
b. Highest temperature at which a substance can exist in the liquid state, regardless of pressure.
c. Temperature at which boiling occurs at 1 atm.
d. Temperature and pressure where solid, liquid, and gas phases are all in equilibrium.
e. Point at which pressure and temperature are less than 0.
9. When the liquid metal mercury, Hg, is placed in a small tube, the meniscus actually curves upward, just
the opposite of water. The reason for this is that
a. The cohesive force is greater than the adhesive force.
b. The adhesive force is greater than the cohesive force.
c. The density of mercury is much larger than the density of water.
d. The density of mercury is much greater where it is in contact with the glass.
e. Mercury is less volatile than water.
10. An aqueous solution of potassium iodide, KI, is heated from 25°C to 85°C. During the time period while
the solution is being heated, which of the following is true?
a. The mole fraction of the solute decreases.
b. The mole fraction of the solvent increases.
c. The density of the solution is constant.
d. The molarity of the solution is constant.
e. The molality of the solution is constant.
11. If you were trying to increase the amount of dissolved carbon dioxide gas in water, which set of
conditions would allow you the highest levels of dissolved CO2?
Pressure
Temperature
of CO2
of H2O (°C)
above water
(atm)
a. 10.0
90
b. 10.0
10
c. 5.0
90
d. 5.0
10
e. 1.0
10
12. Which of the following pairs of liquids forms the most ideal solution (the solution that most closely
follows Raoult’s Law)?
a. C6H14 and H2O
b. CH3CH2CH2OH and H2O
c. CH3CH2OH and C6H14
d. C6H6 and C6H5CH3
e. H3PO4 and H2O
13. Which of the following has the lowest freezing point?
a. 0.50 m C12H22O11
b. 0.50 m KNO3
c. 0.50 m MgSO4
d. 0.50 m Na3PO4
e. 0.50 m K2CrO4
14. 100.0 ml of a 4.00 molar solution of KBr (molar mass 119.0g/mol) would contain _____ of KBr.
a. 2.98 g
b. 4.76 g
c. 47.6 g
d. 476 g
e. 500 g
15. An aqueous solution of silver nitrate (AgNO3, molar mass 169.9 g/mol) is prepared by adding 200.0 g
AgNO3 to 1,000 g H2O. If Kf for water is 1.86°C/m, the freezing point of the solution should be
a. 0.00°C
b. -0.21°C
c. -0.438°C
d. -2.19°C
e. -4.38°C
16. A solution of glucose (molecular weight 180.16 g/mol) in water (molecular weight 18.01 g/mol) is
prepared. The mole fraction of glucose in solution is 0.100. What is the molality of the solution?
a. 0.100m
b. 0.162m
c. 3.09m
d. 6.17m
e. 10.0m
17. Your teacher has asked you to prepare 1.00 L of a 0.100 molar aqueous solution of sodium hydroxide
(molar mass 40.0 g/mol). You should weigh out
a. 4.00 g of NaOH and add 1.00 L of distilled water.
b. 2.50 g of NaOH and add 1.00 L of distilled water.
c. 4.00 g of NaOH and add 1.00 kg of distilled water.
d. 4.00 g of NaOH and add distilled water until the solution has a volume of 1.00 L.
e. 2.50 g of NaOH and add distilled water until the solution has a volume of 1.00 L.
18. Which of the following aqueous solutions has the highest boiling point?
a. 0.10 M NaF
b. 0.1 M of HNO3
c. 0.10 M of NH4OH
d. 0.10 M of MgCl2
e. 0.20 M of C6H12O6
19. The vapor pressure of water at 50°C is 92.5 mmHg. If 400.0 g of sucrose (C12H22O11 molar mass 342.3
g/mol) is added to 900.0 g of H2O at 50°C, what will the vapor pressure of the solution be?
a. 94.6 mmHg
b. 92.3 mmHg
c. 90.4 mmHg
d. 88.3 mmHg
e. 27.4 mmHg
20. How much pure water would 81.1 g of iron (III) chloride (FeCl3 molar mass 162.2 g/mol) be dissolved in
to make a solution with a molality of 1.5m?
a. 333 kg
b. 333 g
c. 3.33 kg
d. 666 g
e. 500 ml
21. What is the osmotic pressure of a 0.100 molar saline solution (NaCl dissolved in H2O) at 27°C?
a. 0.22 atm
b. 0.44 atm
c. 2.5 atm
d. 4.9 atm
e. 9.8 atm
Open Response: Answer on a separate piece of paper:
22. The normal melting and boiling points of oxygen are 55K and 90K, respectively. The triple point is 54K
and 1mmHg (0.0015atm). The critical point is 154K and 50 atm.
a. Use the data above to draw a phase diagram for oxygen. Label the axes and label the regions in
which the solid, liquid, and gas phases are stable.
b. If oxygen is heated from 75K to 130K at 1 atm, describe any changes that may occur.
c. Is the pressure is increased from 1 atm to 40 atm at a constant temperature of 110K, describe any
changes that may occur.
d. How does the density of liquid oxygen compare to the density of solid oxygen? Explain your
answer using both the data and your phase diagram.
23. A 0.562 g sample of an unknown substance was dissolved in 17.4 g of benzene. The freezing point of the
solution was 4.075°C. The freezing point of pure benzene is 5.455°C, Kf = 5.065°C/m, and Kb =
2.61°C/m. Assume that the solute is a nonelectrolyte.
a. What is the molality of the solution?
b. What is the molar mass of the unknown?
c. If the boiling temperature of pure benzene is 80.2°C, what is the boiling temperature of the
solution?
24. A high school student was going to determine the molar mass of an unknown compound by using the
freezing-point depression technique. A sample of solvent was first chilled to its freezing temperature in a
small test tube that was placed within a second test tube as shown in the diagram. Following the initial
trial, a carefully measured amount of water was added to the test tube and the tube and its contents
weighed. A small amount of solute was weighed and added to the test tube containing the water. The
freezing temperature was measured again in the same way as the initial trail with the pure water. Assume
that the solute is an nonelectrolyte, the temperature of the liquid in the small test tube was uniform
throughout, and a graduated cylinder and an analytical balance are available.
a. Write the equation(s) needed to calculate the molar mass of the solute.
b. List the measurements that must be made in order to calculate the molar mass of the solute.
c. Explain the purpose of placing the test tube containing the liquids inside the larger test tube.
d. The student determines the molar mass of the solute to be 170g/mol. Show the setup you would
use to calculate the percent error if the mass of the unknown was actually 180 g/mol (it is not
necessary to perform the calculation).
e. Id the student had used the molarity rather than the molality in the determination of the molar
mass, how would this have affected his results?