Chapter 12 1 Determine the vapor pressure of a solution at 25°C that

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Chemistry: A Molecular Approach, 2e (Tro)

Chapter 12 Solutions

Multiple Choice Questions

1) Choose the statement below that is TRUE.

A) A solution will form between two substances if the solute-solvent interactions are of comparable

strength to the solute-solute and solvent-solvent interactions.

B) A solution will form between two substances if the solute-solvent interactions are small enough to be

overcome by the solute-solute and solvent-solvent interactions.

C) A solution will form between two substances if the solute-solute interactions are strong enough to

overcome the solvent-solvent interactions.

D) A solution will form between two substances only if the solvent-solvent interactions are weak

enough to overcome the solute-solvent interactions.

E) None of the above are true.

2) Give the major force between ethanol and water.

A) dipole-dipole

B) dispersion

C) hydrogen bonding

D) ion-ion

E) ion-dipole

3) Give the major force in seawater.

A) dipole-dipole

B) dispersion

C) hydrogen bonding

D) ion-ion

E) ion-dipole

4) Give the major force between acetone and chloroform.

A) dipole-dipole

B) dispersion

C) hydrogen bonding

D) ion-ion

E) ion-dipole

5) Identify the polar solvent.

A) acetone

B) hexane

C) diethyl ether

D) toluene

E) carbon tetrachloride

6) Which of the following compounds will be most soluble in ethanol (CH3CH2OH)?

A) trimethylamine (N(CH3)3)

B) acetone (CH3COCH3)

C) ethylene glycol (HOCH2CH2OH)

D) hexane (CH3CH2CH2CH2CH2CH3)

E) None of these compounds should be soluble in ethanol.

7) Which of the following compounds is most soluble in hexane (CH3CH2CH2CH2CH2CH2CH3)?

A) methanol

B) ethanol

C) 1-propanol

D) 1-butanol

E) 1-pentanol

8) Choose the situation below that would result in a ΔHsolution near 0.

A) When |ΔHsolvent| >> |ΔHsolute|

B) When |ΔHsolute| > |ΔHhydration|

C) When |ΔHsolute| < |ΔHhydration|

D) When |ΔHsolute| is close to |ΔHhydration|

E) There isn’t enough information to determine.

9) Choose the situation below that would result in an exothermic ΔHsolution.

A) When |ΔHsolute| > |ΔHhydration|

B) When |ΔHsolute| is close to |ΔHhydration|

C) When |ΔHsolute| < |ΔHhydration|

D) When |ΔHsolvent| >> |ΔHsolute|

E) There isn’t enough information to determine.

10) Choose the situation below that would result in an endothermic ΔHsolution.

A) When |ΔHsolute| > |ΔHhydration|

B) When |ΔHsolute| < |ΔHhydration|

C) When |ΔHsolute| is close to |ΔHhydration|

D) When |ΔHsolvent| >> |ΔHsolute|

E) There isn’t enough information to determine.

11) Determine DHsolute for KBr if the DHsolution (KBr) = +19.9 kJ/mol and the

ΔHhydration(KBr) = -670. kJ/mol.

A) +650 kJ/mol

B) -650 kJ/mol

C) +690 kJ/mol

D) -710 kJ/mol

E) -690 kJ/mol

12) A solution containing less than the equilibrium amount is called ________.

A) an unsaturated solution

B) a dilute solution

C) a supersaturated solution

D) a concentrated solution

E) a saturated solution

13) A solution containing more than the equilibrium amount is called ________.

A) an unsaturated solution

B) a dilute solution

C) a supersaturated solution

D) a concentrated solution

E) a saturated solution

14) A solution is formed at room temperature by vigorously dissolving enough of the solid solute so that

some solid remains at the bottom of the solution. Which statement below is TRUE?

A) The solution is considered unsaturated.

B) The solution is considered supersaturated.

C) The solution is considered saturated.

D) The solution would be considered unsaturated if it were cooled a bit to increase the solubility of the

solid.

E) None of the above are true.

15) Which of the following statements is generally TRUE?

A) The solubility of a solid is not dependent on either temperature or pressure.

B) The solubility of a solid is highly dependent on pressure.

C) The solubility of a solid is highly dependent on both pressure and temperature.

D) The solubility of a solid is highly dependent on temperature.

E) None of the above.

16) A solid can be purified through what technique?

A) recrystallization

B) dilution

C) dissolution

D) boiling

E) melting

17) Which of the following statements is TRUE?

A) In general, the solubility of a solid in water decreases with increasing temperature.

B) In general, the solubility of a gas in water decreases with increasing temperature.

C) The solubility of a gas in water usually increases with decreasing pressure.

D) The solubility of an ionic solid in water decreases with increasing temperature.

E) None of the above statements are true.

18) Determine the Henry’s law constant for ammonia in water at 25°C if an ammonia pressure of 0.022

atm produces a solution with a concentration of 1.3 M.

A) 59 M/atm

B) 0.017 M/atm

C) 0.029 M/atm

D) 35 M/atm

E) 0.038 M/atm

19) Calculate the mass of oxygen (in mg) dissolved in a 5.00 L bucket of water exposed to a pressure of

1.13 atm of air. Assume the mole fraction of oxygen in air to be 0.21 and the Henry’s law constant for

oxygen in water at this temperature to be 1.3 × 10-3 M/atm.

A) 49.4 mg

B) 23.5 mg

C) 9.87 mg

D) 27.3 mg

E) 13.7 mg

20) Give the term for the amount of solute in moles per liter of solution.

A) molality

B) molarity

C) mole fraction

D) mole percent

E) mass percent

21) Give the term for the amount of solute in moles per kilogram of solvent.

A) molality

B) molarity

C) mole fraction

D) mole percent

E) mass percent

22) Which of the following concentration units are temperature dependent?

A) mole fraction

B) molality

C) mass percent

D) molarity

E) none of the above.

23) What mass (in g) of NH3 must be dissolved in 475 g of methanol to make a 0.250 m solution?

A) 2.02 g

B) 4.94 g

C) 1.19 g

D) 8.42 g

E) 1.90 g

24) How many moles of KF are contained in 347 g of water in a 0.175 m KF solution?

A) 1.65 × 10-2 mol KF

B) 5.04 × 10-2 mol KF

C) 6.07 × 10-2 mol KF

D) 3.22 × 10-2 mol KF

E) 1.98 × 10-2 mol KF

25) How many moles of KF are contained in 244 mL of 0.135 m KF solution? The density of the

solution is 1.22 g/mL.

A) 4.31 × 10-2 mol KF

B) 4.02 × 10-2 mol KF

C) 3.29 × 10-2 mol KF

D) 2.32 × 10-2 mol KF

E) 1.67 × 10-2 mol KF

26) Calculate the molality of a solution that is prepared by mixing 25.5 mL of CH3OH (d = 0.792 g/mL)

and 387 mL of CH3CH2CH2OH (d = 0.811 g/mL).

A) 0.630 m

B) 0.812 m

C) 1.57 m

D) 2.01 m

E) 4.98 m

27) Determine the molality of a solution prepared by dissolving 0.500 moles of CaF2 in 11.5 moles

H2O.

A) 1.88 m

B) 4.35 m

C) 5.31 m

D) 4.14 m

E) 2.41 m

28) Determine the molality of an aqueous solution prepared by dissolving 0.112 moles of LiCl in 13.7

moles of H2O.

A) 0.454 m

B) 0.220 m

C) 0.818 m

D) 0.122 m

E) 0.153 m

29) Commercial grade HCl solutions are typically 39.0% (by mass) HCl in water. Determine the

molarity of the HCl, if the solution has a density of 1.20 g/mL.

A) 7.79 M

B) 10.7 M

C) 12.8 M

D) 9.35 M

E) 13.9 M

30) A solution is prepared by dissolving 98.6 g of NaCl in enough water to form 875 mL of solution.

Calculate the mass % of the solution if the density of the solution is 1.06 g/mL.

A) 11.3%

B) 12.7%

C) 9.4%

D) 10.6%

E) 11.9%

31) A solution is prepared by dissolving 49.3 g of KBr in enough water to form 473 mL of solution.

Calculate the mass % of KBr in the solution if the density is 1.12 g/mL.

A) 10.4%

B) 8.57%

C) 10.1%

D) 11.7%

E) 9.31%

32) What mass of NaCl is contained in 24.88 g of a 15.00% by mass solution of NaCl in water?

A) 20.00 g

B) 21.15 g

C) 3.73 g

D) 1.50 g

E) 12.44 g

33) A solution is prepared by dissolving 38.6 g sucrose (C12H22O11) in 495 g of water. Determine the

mole fraction of sucrose if the final volume of the solution is 508 mL.

A) 4.09 × 10-3

B) 7.80 × 10-2

C) 1.28 × 10-3

D) 7.23 × 10-2

E) 2.45 × 10-3

34) A solution is prepared by dissolving 76.3 g NaI in 545 g of water. Determine the mole fraction of

NaI if the final volume of the solution is 576 mL.

A) 6.04 × 10-3

B) 1.65 × 10-2

C) 1.40 × 10-3

D) 1.32 × 10-2

E) 8.84 × 10-2

35) A 4.55 L sample of water contains 0.115 g of sodium ions. Determine the concentration of sodium

ions in ppm if the density of the solution is 1.00 g/mL.

A) 52.3 ppm

B) 13.2 ppm

C) 12.7 ppm

D) 25.3 ppm

E) 36.5 ppm

36) What mass of ethane (CH3CH3) is contained in 50.0 mL of a 13.9% by mass solution of ethane in

hexane? The density of the solution is 0.611 g/mL.

A) 2.35 g

B) 8.49 g

C) 11.8 g

D) 6.95 g

E) 4.25 g

37) Commercial grade HCl solutions are typically 39.0% (by mass) HCl in water. Determine the

molality of the HCl, if the solution has a density of 1.20 g/mL.

A) 39.0 m

B) 17.5 m

C) 6.39 m

D) 10.7 m

E) 9.44 m

38) Identify the colligative property.

A) vapor pressure lowering

B) freezing point depression

C) boiling point elevation

D) osmotic pressure

E) all of the above

39) ________ is applied to roads in wintertime so that the ice will melt at a lower temperature.

A) Antifreeze

B) Water

C) Salt

D) Sugar

E) Oil

40) Determine the vapor pressure of a solution at 25°C that contains 76.6 g of glucose (C6H12O6) in

250.0 mL of water. The vapor pressure of pure water at 25°C is 23.8 torr.

A) 70.8 torr

B) 72.9 torr

C) 23.1 torr

D) 22.9 torr

E) 7.29 torr

41) Determine the freezing point depression of a solution that contains 30.7 g glycerin (C3H8O3, molar

mass = 92.09 g/mol) in 376 mL of water. Some possibly useful constants for water are Kf = 1.86°C/m

and Kb = 0.512°C/m.

A) 0.887°C

B) 1.65°C

C) 3.33°C

D) 3.33°C

E) 0.654°C

42) Determine the freezing point of a solution that contains 78.8 g of naphthalene (C10H8, molar mass =

128.16 g/mol) dissolved in 722 mL of benzene (d = 0.877 g/mL). Pure benzene has a melting point of

5.50°C and a freezing point depression constant of 4.90°C/m.

A) 4.76°C

B) 4.17°C

C) 0.74°C

D) 1.33°C

E) 1.68°C

43) Calculate the freezing point of a solution of 500.0 g of ethylene glycol (C2H6O2) dissolved in 500.0

g of water. Kf = 1.86°C/m and Kb = 0.512°C/m.

A) 30.0°C

B) -30.0°C

C) 8.32°C

D) -8.32°C

E) 70.2°C

44) Calculate the boiling point of a solution of 500.0 g of ethylene glycol (C2H6O2) dissolved in 500.0

g of water. Kf = 1.86°C/m and Kb = 0.512°C/m. Use 100°C as the boiling point of water.

A) 108°C

B) 92°C

C) 130°C

D) 70°C

E) 8.3°C

45) The boiling point elevation of an aqueous sucrose solution is found to be 0.39°C. What mass of

sucrose (molar mass= 342.30 g/mol) would be needed to dissolve in 500.0 g of water? Kb (water) =

0.512°C/m.

A) 261 g sucrose

B) 528 g sucrose

C) 762 g sucrose

D) 223 g sucrose

E) 130. g sucrose

46) Determine the boiling point of a solution that contains 78.8 g of naphthalene (C10H8, molar mass =

128.16 g/mol) dissolved in 722 mL of benzene (d = 0.877 g/mL). Pure benzene has a boiling point of

80.1°C and a boiling point elevation constant of 2.53°C/m.

A) 2.2°C

B) 2.5°C

C) 82.3°C

D) 80.4°C

E) 82.6°C

47) Give the reason that antifreeze is added to a car radiator.

A) The freezing point is lowered and the boiling point is elevated.

B) The freezing point is elevated and the boiling point is lowered.

C) The freezing point and the boiling point are elevated.

D) The freezing point and the boiling point are lowered.

E) None of the above.

48) A compound is found to have a molar mass of 598 g/mol. If 35.8 mg of the compound is dissolved

in enough water to make 175 mL of solution at 25°C, what is the osmotic pressure of the resulting

solution?

A) 3.42 torr

B) 6.36 torr

C) 5.01 torr

D) 5.99 torr

E) 8.36 torr

49) A 150.0 mL sample of an aqueous solution at 25°C contains 15.2 mg of an unknown nonelectrolyte

compound. If the solution has an osmotic pressure of 8.44 torr, what is the molar mass of the unknown

compound?

A) 223 g/mol

B) 294 g/mol

C) 341 g/mol

D) 448 g/mol

E) 195 g/mol

50) Determine the vapor pressure of a solution at 55°C that contains 34.2 g NaCl in 375 mL of water.

The vapor pressure of pure water at 55°C is 118.1 torr. The van’t Hoff factor for NaCl is 1.9

A) 115 torr

B) 87.1 torr

C) 108 torr

D) 112 torr

E) 92.8 torr

51) The boiling point of an aqueous 1.83 m (NH4)2SO4 (molar mass = 132.15 g/mol) solution is

102.5°C. Determine the value of the van’t Hoff factor for this solute if the Kb for water is 0.512°C/m.

A) 3.0

B) 3.6

C) 1.8

D) 2.7

E) 2.3

52) Fluids used for an intravenous transfusion must be ________ with bodily fluids.

A) isosmotic

B) hyperosmotic

C) hyposmotic

D) neosmotic

E) magnosmotic

53) Solutions having osmotic pressures less than those of body fluids are called ________.

A) isosmotic

B) hyperosmotic

C) hyposmotic

D) neosmotic

E) magnosmotic

54) Identify the classification of milk.

A) aerosol

B) solid aerosol

C) foam

D) emulsion

E) solid emulsion

55) Identify the classification of opal.

A) aerosol

B) solid aerosol

C) foam

D) emulsion

E) solid emulsion

56) Identify the classification of whipped cream.

A) aerosol

B) solid aerosol

C) foam

D) emulsion

E) solid emulsion

57) Soap has an ionic and a polar end. It works well to remove oil by

A) surrounding the oil with the nonpolar end, and the water interacts with the polar end.

B) surrounding the oil with the polar end, and the water interacts with the nonpolar end.

C) surrounding the oil and water with the polar end.

D) surrounding the oil and water with the nonpolar end.

Algorithmic Questions

1) Which of the following compounds will be most soluble in nonane (C9H20)?

A) pentanol (CH3CH2CH2CH2CH2OH)

B) benzene (C6H6)

C) acetic acid (CH3CO2H)

D) ethyl methyl ketone (CH3CH2COH3)

E) None of these compounds should be soluble in pentane.

2) Identify the compounds that are soluble in both water and hexane.

A) methanol and 1-pentanol

B) ethanol and 1-butanol

C) 1-propanol and 1-butanol

D) 1-butanol and 1-pentanol

E) ethanol and 1-propanol

3) Which of the following ions should have the most exothermic ΔHhydration?

A) Na⁺

B) Ba2⁺

C) Al3⁺

D) Ca2⁺

E) Sr2⁺

4) Which cation in each set is expected to have the larger (more negative) hydration energy?

I Be2+ or Ca2+

II Rb+ or Zn2+

A) Be2+ in set I and Rb+ in set II

B) Be2+ in set I and Zn2+ in set II

C) Ca2+ in set I and Rb+ in set II

D) Ca2+ in set I and Zn2+ in set II

5) The Henry’s Law constant of methyl bromide, CH3Br, is k = 0.159 mol/(L ∙ atm) at 25°C. What is the

solubility of methyl bromide in water at 25°C and at a partial pressure of 270. mm Hg?

A) 0.0565 mol/L

B) 0.355 mol/L

C) 0.448 mol/L

D) 42.9 mol/L

6) The Henry’s law constant for helium gas in water at 30°C is 3.70 × 10-4 M/atm. When the partial

pressure of helium above a sample of water is 0.650 atm, the concentration of helium in the water is

________ M.

A) 5.69 × 10-4

B) 1.76 × 103

C) 1.30

D) 2.41 × 10-4

E) 3.70 ×

7) Dynamic equilibrium can be defined as

A) rate of dissolution = rate of deposition

B) rate of dissolution < rate of deposition

C) rate of dissolution > rate of deposition

D) rate of bubbling > rate of dissolving

E) rate of condensing > rate of bubbling

8) Dissolving can be defined as

A) rate of dissolution = rate of deposition

B) rate of dissolution < rate of deposition

C) rate of dissolution > rate of deposition

D) rate of bubbling > rate of dissolving

E) rate of condensing > rate of bubbling

9) Identify the compound whose solubility is least affected by temperature.

A) K Cl

B) K2Cr2O7

C) NaNO3

D) Pb(NO3)3

E) NaCl

10) Identify the compound whose solubility decreases with increasing temperature.

A) Na2SO4

B) K2Cr2O7

C) NaNO3

D) KClO3

E) CaCl2

11) Identify the gas that is dissolved in carbonated sodas.

A) carbon dioxide

B) hydrogen

C) neon

D) carbon monoxide

E) argon

12) 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

13) Determine the solubility of N2 in water exposed to air at 25°C if the atmospheric pressure is 2.0 atm.

Assume that the mole fraction of nitrogen is 0.78 in air and the Henry’s law constant for nitrogen in

water at this temperature is 6.1 × 10-4 M/atm.

A) 1.6 × 10-4 M

B) 6.4 × 10-4 M

C) 9.5 × 10-4 M

D) 1.1 × 10-4 M

E) 1.2 × 10-4 M

14) Determine the solubility of CO2 in soda water at 25°C if the pressure of CO2 is 5.6 atm. The

Henry’s law constant for carbon dioxide in water at this temperature is 3.4 × 10-2 M/atm.

A) 0.16 M

B) 0.53 M

C) 0.61 M

D) 0.19 M

E) 0.78 M