[Chapter 11 Worksheet 2]
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Chapter 11-Part 2
Question 1: What are the ideal van’t Hoff factors for these compounds: Ba(OH)2, C6H12O6, K3PO4, HNO3 ?
A. 1, 1, 1, 1
B. 2, 1, 2, 2
C. 3, 1, 4, 2
D. 6, 3, 5, 5
E. none of the above
Question 2: Rank the following solutions from lowest boiling point to highest boiling point.
A. 0.35 m Ethylene Glycol (C2H6O2)
B. 0.20 m KBr
C. 0.50 m Glucose (C6H12O6)
D. 0.20 m Na2SO4
Question 3: Choose the aqueous solution with the lowest vapor pressure. These are all solutions of
nonvolatile solutes and you should assume ideal van’t Hoff factors where applicable.
A. 0.120 m C2H6O2
B. 0.040 m (NH4)2SO4
C. 0.060 m Li2CO3
D. 0.030 m RbC2H3O2
E. They all have the same vapor pressure.
Question 4: Which of the following should have the largest Henry’s law constant (kH) in water?
A. Ne
B. CO
C. Br2
D. CH3CH3
E. CO2
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Question 5: The diagram shows a closed system containing two salt water solutions. The solution labeled A is
more concentrated than the one labeled B. Which of the diagrams below best represents the system at an
infinite time after preparation?
Question 6: What is the vapor pressure of a solution that is 30.3% w/w ethylene glycol (MW = 62.07 g/mol) in
water at 90 °C. The vapor pressure of pure water is 525.8 torr at 90 °C.
mm Hg
Question 7: What is the vapor pressure of a solution that is 30.3% w/w ethylene glycol (MW = 62.07g/mol) in
water at 100 °C.
Torr
Question 8: As the water evaporates from this saturated solution
A. the vapor pressure above the solution increases.
B. the vapor pressure above the solution decreases.
C. the vapor pressure above the solution remains constant.
Question 9: The concentration of alcohol in adult beverages is typically expressed as proof. Proof is simply
double the % by volume (% v/v). Assuming that vodka is a solution of only water and ethanol, what is the total
vapor pressure above an 80 proof vodka at 25 °C?
Water: density = 1.00 g/mL; VP @ 25 °C = 23.8 mm Hg; MW = 18 g/mol
Ethanol: density = 0.789 g/mL; VP @ 25 °C = 58.7 mm Hg; MW = 46 g/mol
2
mm Hg
Question 10: 6. A 2.0 molal aqueous solution of glucose (C6O6H12) is found to
boil at 101 oC. What would the boiling point of a 2.0 molal solution of sucrose
be?
A.
B.
C.
D.
E.
102 oC
100.5 oC
101 oC
Slightly higher than 100.5 oC
Cannot determine without Kb
glucose (C6O6H12)
sucrose (C12O11H22)
Question 11: Last year the lowest temperature in Athens was 12 °F
(-11 °C). What is the minimum concentration for the radiator fluid in your car so that the solution doesn’t
freeze? Radiator fluid is ethylene glycol (MW 62.07 g/mol) dissolved in water. The Kfp for water is -1.86 °C/m.
m
Question 12: A 0.100 M acetic acid solution has an osmotic pressure of 2.47 atm at 25 °C. Calculate the
van’t Hoff factor.
no unit
B. What is the percent ionization of acetic acid in the solution?
%
Question 13: An isotonic solution will produce an osmotic pressure of 7.84 atm measured against pure water at
human body temperature (37.0 °C). How many grams of sodium chloride must be dissolved in a liter of water
to produce an isotonic solution?
grams
Question 14: The smell of ripe raspberries is due to 4-(p-hydroxyphenyl)-2-butanone, which has the empirical
formula C5H6O. To find its molecular formula, you dissolve 0.135 g in 25.0 g of chloroform, CHCl3. The boiling
point of the solution is 61.82 °C. What is the molecular formula of the solute?
CHCl3: BP = 61.70 °C; Kbp = +3.63 °C/m
Question 15: Only the solutes are shown in the following solutions. Which lettered beaker has the lowest vapor
pressure?
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A.
B.
Question 16: The freezing point of a solution is lower than that of the pure solvent because
A. The addition of solute to the liquid increases the rate of escape of molecules from the solid
phase to the liquid phase. At lower temperature these rates can again become equal.
B. The addition of solute to the liquid decreases the rate at which solvent molecules enter the
solid phase. By lowering the temperature, the rate of escape of molecules from the solid to
liquid phase is also lowered and become equal.
For Questions 17-21, match the following.
A. solution with ΔTb = 0.026 °C
B. solution of ionic compound with highest freezing point
C. highest boiling point
D. largest van’t Hoff factor
E. solution that is most strongly dependent upon pressure
Question 17: 0.050 m NaCl
Question 18: 0.050 m C6H12O6 (aqueous)
Question 19: 0.0050 m CO2
Question 20: 0.020 m NH4Cl
Question 21:
0.010 m Al(NO3)3
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Question 22:
A dilute aqueous solution of an organic compound is formed by dissolving 2.35 g of the compound in water to
form 250 mL solution. The resulting solution has an osmotic pressure of 0.605 atm at 25 °C. What is the molar
mass of this compound?
A. 7.97 g/mol
B. 31.9 g/mol
C. 57.5 g/mol
D. 230 g/mol
E. 380 g/mol
Question 23:
The boiling point of ethanol, CH3CH2OH, is 78.500 oC at 1 atm. When 14.10 g of an unknown, non-electrolyte
compound was dissolved in 282.0 g of ethanol, the solution was found to have a boiling point of 78.833 oC.
What is the molar mass of the unknown compound? (Kbp for ethanol = 1.22 oC/m)
A. 68.65 g/mol
B. 84.40 g/mol
C. 145.68 g/mol
D. 174.46 g/mol
E. 183.18 g/mol
Question 24:
Two aqueous are prepared: 1.00 m Na2CO3 and 1.00 m LiCl. Which of the following statements is true?
A. The Na2CO3 solution has a higher osmotic pressure and higher vapor pressure than the LiCl
solution.
B. The Na2CO3 solution has a higher osmotic pressure and higher boiling point than the LiCl
solution.
C. The Na2CO3 solution has a lower osmotic pressure and lower vapor pressure than the LiCI
solution.
D. The Na2CO3 solution has a lower osmotic pressure and higher boiling point than the LiCl
solution.
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