AP Chemistry
Worksheet 11-2
Name :
Date :
A. Multiple choice : Calculators may not be used on the multiple choice.
_____ 1. Which of the following favor the solubility of an ionic solute in a liquid?
I. a large energy of solvation (hydration)
II. a large lattice energy of the solute
III. a large polarity of the solvent
a. I only
b. I and II
c. II only d. III only
e. I and III f. II and III
_____ 2. Which of the following compounds is not soluble in water, but is soluble in dilute hydrochloric acid?
a. Ca3(PO4)2
b. NH4OH
c. (NH4) 2S
d. Ba(NO3) 2
e. Mg(C2H3O2) 2
_____ 3. What is the final concentration of silver ions when 10.0 mL of 0.20 M sodium phosphate is added to 90.0
mL of 0.10 M silver acetate?
a. 0.015 M Ag+
b. 0.030 M Ag+
c. 0.045M Ag+
d. 0.060 M Ag+
e. 0.15 M Ag+
_____ 4. The volume of distilled water that needs to be added to 50.0 mL of 0.20 M NaOH to get a 0.050 M
solution is
a. 20.0 mL
b. 200. mL
c. 150. mL
d. 15.0 mL
e. 450. mL
_____ 5. A solution of barium hydroxide (MW = 171.35) is formed by dissolving 34.3 grams of barium hydroxide
in 500. mL of water. What is the normality of this solution?
a. 0.10 N
b. 0.20 N
c. 0.30 N
d. 0.40 N
e. 0.80 N
_____ 6. What is the mole fraction of ethanol in a solution formed by adding 69.1 grams of ethanol (C2H5OH, MW
= 46.08g) to 18.0 grams of water?
a. 0.25
b. 0.30
c. 0.50
d. 0.60
e. 0.75
_____ 7. CH3CH2CH2CH2CH3 (X), CH3CH2CH2CH2OH (Y), HOCH3CH2CH2OH (Z)
Based on concepts of polarity and hydrogen bonding, which of the following sequences correctly lists
the compounds above in the order of their increasing solubility in water?
a.
Z<Y<X
b. Y<Z<X
c. Y<X<Z
d. X<Z<Y
e. X<Y<Z
_____ 8. The energy change that occurs in the conversion of an ionic solid to widely separated gaseous ions is:
a. activation energy b. free energy c ionization energy d. kinetic energy e. lattice energy
_____ 9. A student wishes to prepare 2.0 liters of 0.10-molar KIO3( molecular weight 214). The proper
procedure is to weigh out:
(A) 42.8 g of KIO3 and add 2.0 kilograms of water
(B) 42.8 g of KIO3 and add water until the final homogeneous solution has a volume of 2.0 liters
(C) 21.4 g of KIO3 and add water until the final homogeneous solution has a volume of 2.0 liters
(D) 42.8 g of KIO3 and add 2.0 liters of water
(E) 21.4 g of KIO3 and add 2.0 liters of water
10. A solution is made by dissolving 25.8 g urea (CH4N2O), a nonelectrolyte, in 275 g water. Calculate the vapor
pressures of this solution at 25°C and 45°C. (The vapor pressure of pure water is 23.8 torr at 25°C and 71.9 torr at
45°C.)
11. Pentane (C5H12) and hexane (C6H14) form an ideal solution. At 25°C the vapor pressures of pentane and hexane are
511 and 150. torr, respectively. A solution is prepared by mixing 25 mL pentane (density, 0.63 g/mL) with 45 mL
hexane (density, 0.66 g/mL).
a. What is the vapor pressure of the resulting solution?
b. What is the composition by mole fraction of pentane in the vapor that is in equilibrium with this solution?
12. What is the composition of a pentane-hexane solution that has a vapor pressure of 350. torr at 25°C? What is
the composition of the vapor in equilibrium with this solution? (Vapor pressures of pentane and hexane are
511 and 150. torr, respectively).
13. Which of the following will have the lowest total vapor pressure at 25°C?
a. Pure water (vapor pressure = 23.8 torr at 25°C)
b. A solution of glucose in water with XC6H12O6 = 0.01
c. A solution of sodium chloride in water with XNaCl = 0.01
d. A solution of methanol in water with XCH3OH = 0.2 [Consider the vapor pressure of both methanol (143 torr at
25°C) and water.]
14. Which of the choices in Exercise 13 has the highest vapor pressure?
15. A solution is made by mixing 50.0 g acetone (CH3COCH3) and 50.0 g methanol (CH3OH). What is the vapor
pressure of this solution at 25°C? What is the composition of the vapor expressed as a mole fraction?
Assume ideal solution and gas behavior. (At 25 °C the vapor pressures of pure acetone and pure methanol
are 271 and 143 torr, respectively.) The actual vapor pressure of this solution is 161 torr. Explain any discrepancies.
16. For each case choose the pair of substances you would expect to give the most nearly ideal solution. Explain
your choices.
O
║
a. CF3CF3 and CF3CF2CF3 or H2O and CH3CCH3
b. CH3(CH2)5CH3 and CH3(CH2)4CH3 or
CHF3 and CH3—O—CH3
c. H3PO4 and H2O or CC14 and CF4
Colligative Properties
17. A solution is prepared by dissolving 4.9 g sucrose (C12H22O11) in 175 g water. Calculate the boiling point of this
solution. Sucrose is a nonelectrolyte.(Kb for water is 0.512 ºC/m)
18. Calculate the freezing point and boiling point of an antifreeze solution that is 40.0% by mass of ethylene
glycol (HOCH2CH2OH, FW= 62.08 g/mol) in water. Ethylene glycol is a nonelectrolyte. (Kf for water = 1.86 ºC/m)
19. Reserpine is a natural product isolated from the roots of the shrub Rauwolfia serpentina. It was first
synthesized in 1956 by Nobel Prize winner R. B. Woodward. It is used as a tranquilizer and sedative. When 1.00
g reserpine is dissolved in 25.0 g camphor, the freezing-point depression is 2.63°C (Kf for camphor is 40.°C •
kg/mol). Calculate the molality of the solution and the molar mass of reserpine.
20. a. Calculate the freezing-point depression and osmotic pressure at 25°C of an aqueous solution containing 1.0 g/L
of a protein (molar mass = 9.0 x 104 g/mol) if the density of the solution is 1.0 g/cm3.
b. Considering your answer to part a, which colligative property, freezing-point depression or osmotic pressure,
would be better used to determine the molar masses of large molecules? Explain.
21. How would you prepare 1.0 L of an aqueous solution of sucrose (Cl2H22O11) having an osmotic pressure of 15.0
atm at a temperature of 22°C? Sucrose is a nonelectrolyte.
22. Describe a laboratory procedure to determine the mole fraction of a nonvolatile, nonelectrolyte substance in
aqueous solution.
23. Describe a laboratory procedure to determine the molality of a nonvolatile, nonelectrolyte substance in
aqueous solution.
.
V
L
V = 0.69 Xhex
Answers : 10. 25 ºC = 23.2 torr; 45 ºC = 70.1 torr 11a. 290 torr
11b. Xpent
= 0.32 12. solution : Xpent
L
V
V = 0.809 and Xhex
V = 0.191
= 0.554 and Xhex = 0.446 ; Vapor : Xpent
13. c.
14. d.
15. 188.7 torr Xacetone
V
= 0.511, Xmeth = 0.489 The calculated vapor pressure assumes ideal behavior. A lower than expected vapor
pressure (Negative deviation from Raoult’s law) indicates stronger solute-solvent interactions than solute-solute
and solvent-solvent interactions. 16a. CF3CF3 and CF3CF2CF3 16b. CH3(CH2)5CH3 and CH3(CH2)4CH3
16c. CC14 and CF4
17. 100.042 ºC
18. F. pt. = -19.9 ºC, B. pt. = 105.48 ºC
19. m =
0.066, 590 g/mol 20a. 2.1 x 10-5 ºC, π = 0.20 torr
20b. Osmotic pressure – larger value, easier to
measure with a lower relative error. 21. Dissolve 212 grams of sucrose in enough water to form one-liter
of solution in a volumetric flask.