Deck 13: Mixtures at the Molecular Level: Properties of Solutions

Question 1

Wax is a solid mixture of hydrocarbon compounds consisting of molecules with long chains of carbon atoms. Which solvent would you expect to be most capable of dissolving wax?

A)
B)
C)
D)
E)

Answer 1

Question 2

Wax is a solid mixture of hydrocarbon compounds consisting of molecules with long chains of carbon atoms. Which solvent would you expect to be most capable of dissolving wax?

A)H-O-H
B)CH₃-O-H
C)CF₃-O-H
D)H-O-CH₂-CH₂-O-H
E)CH₃-CH₂-CH₂-CH₂-CH₂-H₂-CH₂-CH₃

Answer 2

CH₃-CH₂-CH₂-CH₂-CH₂-H₂-CH₂-CH₃

Question 3

Which response lists all the following pairs that are miscible liquids?
Pair 1. octane (C₈H₁₈)and water
Pair 2. ammonia (NH₃)and water
Pair 3. octane (C₈H₁₈)and carbon tetrachloride (CCl₄)

A)1, 3
B)1, 2
C)2
D)2, 3
E)3

Answer 3

2, 3

Question 4

Concerning the process of separating of a solid substance into its component units (molecules or ions),

A)the process is exothermic and the potential energy increases.
B)the process is exothermic and the potential energy decreases.
C)the process is endothermic and the potential energy increases.
D)the process is endothermic and the potential energy decreases.
E)the process is endothermic and occurs with no change in potential energy.

Question 5

Concerning the solvation step of the solution process,

A)the process is exothermic and the potential energy increases.
B)the process is exothermic and the potential energy decreases.
C)the process is endothermic and the potential energy increases.
D)the process is endothermic and the potential energy decreases.
E)the process is endothermic and occurs with no change in potential energy.

Question 6

KBr has a lattice energy of -682 kJ/mol and a hydration energy of -657 kJ/mol. Using this information, what is the heat of solution, $\Delta$ H_sol, for KBr?Hint: What happens to the crystal lattice when an ionic compound dissolves?

A)-1339 kJ/mol
B)+1339 kJ/mol
C)+25 kJ/mol
D)-657 kJ/mol
E)+657 kJ/mol

Question 7

A solution in a beaker has some undissolved solute lying on the bottom of the beaker. If the rate of crystallization exceeds the rate of dissolution of the excess solute, the solution is described as

A)dilute.
B)concentrated.
C)unsaturated.
D)saturated.
E)supersaturated.

Question 8

A solution in a beaker has some un-dissolved solute lying on the bottom of the beaker. If the rate of crystallization is equal to the rate of dissolution of the excess solute, the solution is described as

A)dilute.
B)concentrated.
C)unsaturated.
D)saturated.
E)supersaturated.

Question 9

A solution in a beaker has some un-dissolved solute lying on the bottom of the beaker. If the rate of dissolution of the solute exceeds the rate of crystallization, the solution is described as

A)dilute.
B)concentrated.
C)unsaturated.
D)saturated.
E)supersaturated.

Question 10

A solution is sitting undisturbed on a side shelf in the laboratory. A small crystal of the same solute of which the solution is made was gently dropped into the solution. Suddenly, a mass of crystals forms and settles to the bottom of the container. The solution is, or must have been

A)dilute.
B)concentrated.
C)unsaturated.
D)saturated.
E)supersaturated.

Question 11

Which of the following will always cause an increase in the solubility of a gas in a solvent in which the gas does not react with the solvent to form a new substance?

A)increasing the temperature of the solvent and simultaneously decreasing the pressure of the gas in the space above the solvent
B)decreasing the temperature of the solvent and simultaneously increasing the pressure of the gas in the space above the solvent
C)increasing the temperature of the solvent and simultaneously increasing the pressure of the gas in the space above the solvent
D)decreasing the temperature of the solvent and simultaneously decreasing the pressure of the gas in the space above the solvent
E)increasing the temperature of the solvent while maintaining the pressure of the gas in the space above the solvent at a set value

Question 12

The solubility of O₂ in water is approximately 0.00380 g L^-1 when the temperature is 25.0°C and the partial pressure of gaseous oxygen is 760. torr. What will the solubility of oxygen be if the oxygen pressure is adjusted to 1000 torr?

A)0.00289 g L^-1
B)0.00500 g L^-1
C)1.49 g L^-1
D)2.89 × 10³ g L^-1
E)3.46 × 10³ g L^-1

Question 13

The solubility of O₂ in water is approximately 0.00380 g L^-1 of water when the temperature is 25.0°C and the partial pressure of gaseous oxygen is 760 torr. The oxygen gas above the water is replaced by air at the same temperature and pressure, in which the mole fraction of oxygen is 0.210. What will the solubility of oxygen in water be under these new conditions?

A)1.05 × 10^-6 g L^-1
B)7.98 × 10^-4 g L^-1
C)1.33 × 10^-3 g L^-1
D)0.606 g L^-1
E)1.01 g L^-1

Question 14

A solution is made by mixing 138.2 grams of ethanol, C₂H₆O, (46.069 g mol^-1); 103.6 grams of water (18.015 g mol^-1), and 80.11 grams of methanol, CH₄O, (32.042 g mol^-1). What is the mole fraction of methanol in the mixture?

A)0.02504
B)0.2222
C)0.2493
D)0.3333
E)0.4490

Question 15

The CO₂ gas sealed inside a carbonated beverage bottle has a pressure of 3.750 atm. At this pressure, the solubility of CO₂ in water is 0.65 g CO₂/100 g H₂O. If the bottle is opened, as the gas in the space above the liquid escapes, the partial pressure of the CO₂ falls to 0.30 torr, the value in the surrounding atmosphere of the room. What is the solubility of CO₂ in the beverage at this new pressure?Hint: Be sure check your pressure units.

A)5.2 × 10^-2 g/100 g H₂O
B)5.0 × 10^-4 g/100 g H₂O
C)6.7 × 10^-5 g/100 g H₂O
D)6.8 × 10^-5 g/100 g H₂O
E)9.6 × 10^-4 g/100 g H₂O

Question 16

A solution of sodium nitrite is prepared by mixing 3.25 g of NaNO₂ with 12.0 g of water. The percent, by mass, of NaNO₂ is

A)28.0%.
B)23.3%.
C)27.0%.
D)21.3%.
E)37.1%.

Question 17

A solution of lithium hydroxide is prepared by mixing 2.00 g of LiOH with 10.0 g of water. The percent, by mass, of LiOH is

A)10.7%.
B)12.0%.
C)16.7%.
D)20.0%.
E)80.0%.

Question 18

How many grams of NaC₂H₃O₂ should be dissolved in 400.0 g of water to prepare a solution that is 11.28% NaC₂H₃O₂ by mass?

A)3.146 g
B)7.558 g
C)21.17 g
D)50.86 g
E)127.15 g

Question 19

A solution of potassium nitrate is prepared by mixing 3.50 g of KNO₃ with 12.0 g of water. The percent, by mass, of KNO₃ is

A)22.6%.
B)23.3%.
C)28.0%.
D)29.2%.
E)41.8%.

Question 20

A glucose solution is prepared by dissolving 5.10 g of glucose, C₆H₁₂O₆, in 110.5 g of water. What is the molality of the glucose solution?

A)0.283 m
B)0.000256 m
C)0.245 m
D)0.256 m
E)0.351 m

Question 21

An aqueous solution of orthophosphoric acid, H₃PO₄, has a measured density of 1.2089 g mL^-1 and is 5.257 molal. How many moles of H₃PO₄ are there in one liter of this solution?

A)0.4261 moles
B)4.194 moles
C)4.349 moles
D)5.152 moles
E)6.355 moles

Question 22

An aqueous solution of ethanol, C₂H₅OH, is 19.00% ethanol by mass and has a density of 0.9700 g mL^-1. Calculate the molality of the ethanol solution.

A)4.000 m
B)4.124 m
C)4.252 m
D)5.092 m
E)14.48 m

Question 23

An aqueous solution of glycerol, C₃H₈O₃, is 48.0% glycerol by mass and has a density of Calculate the molality of the glycerol solution.

A)11.2 m
B)5.84 m
C)0.584 m
D)0.521 m
E)10.0 m

Question 24

A solution is prepared by mixing 0.3355 moles of NaNO₃ (84.995 g mol^-1)with 235.0 g of water (18.015 g mol^-1). Its density is 1.0733 g mL^-1. What is the percent by mass of NaNO₃ in the solution?

A)10.16%
B)10.82%
C)11.61%
D)14.19%
E)26.56%

Question 25

A solution is prepared by mixing 0.3355 moles of NaNO₃ (84.995 g mol^-1)with 235.0 g of water (18.015 g mol^-1). Its density is 1.0733 g mL^-1. What is the molality of the solution?

A)0.6474 m
B)0.7004 m
C)1.320 m
D)1.428 m
E)1.545 m

Question 26

An aqueous solution is prepared by mixing 0.2750 moles of NaOH (40.00 g mol^-1)with 189.0 g of water. Its density is 1.065 g mL^-1. What is the percent by weight of NaOH in the solution?

A)0.001375%
B)5.500%
C)5.858%
D)13.75%
E)20.00%

Question 27

An aqueous solution of nitric acid has a density of 1.084 g mL^-1 and a measured concentration of 2.580 molar. What is the percent by weight of nitric acid in the solution?

A)2.380%
B)13.82%
C)15.00%
D)22.29%
E)44.38%

Question 28

Which is a concentration unit whose value changes if the temperature of an aqueous solution is changed?

A)mole fraction
B)molarity
C)molality
D)mass fraction
E)percent by weight

Question 29

Consider a 0.900 M Al(NO₃)₃ solution. This solution has a nitrate ion concentration of

A)0.300 M.
B)0.900 M.
C)2.70 M.
D)3.60 M.
E)8.10 M.

Question 30

A solution of ethylene glycol (C₂H₆O₂)in water is 3.981 molar and has a density of Calculate the percent, by weight, of ethylene glycol in the solution.

A)3.867%
B)4.099%
C)15.14%
D)24.00%
E)25.45%

Question 31

A solution of sodium nitrate, NaNO₃, in water is 5.181 molar and its density is 1.2680 g mL^-1. Calculate the percent, by weight, of sodium nitrate in the solution.

A)7.939%
B)17.21%
C)24.47%
D)29.56%
E)34.73%

Question 32

An aqueous solution of ethanol, C₂H₅OH, is 19.00% ethanol by mass and has a density of 0.9700 g mL^-1. Calculate the molarity of the ethanol solution.

A)4.001 M
B)4.124 M
C)4.252 M
D)5.092 M
E)14.48 M

Question 33

An aqueous solution of glycerol, C₃H₈O₃, is 48.0% glycerol by mass andhas a density of 1.120 g mL^-1. Calculate the molarity of the glycerol solution.

A)12.2 M
B)5.84 M
C)0.584 M
D)0.521 M
E)0.465 M

Question 34

A solution is prepared by mixing 0.3355 moles of NaNO₃ (84.995 g mol^-1)with 235.0 g of water (18.015 g mol^-1). Its density is 1.0733 g mL^-1. What is the molarity of the solution?

A)1.186 M
B)1.273 M
C)1.350 M
D)1.366 M
E)1.428 M

Question 35

An aqueous solution of glycerol, C₃H₈O₃, in which the mole fraction of C₃H₈O₃ is 0.07070 was found to have a density of 1.0350 g mL^-1. What is the molarity of this solution?Hint: Assume one mole of glycerol and solve for moles of water. From there you can find the mass and then volume of the solution.

A)3.147 molar
B)4.371 molar
C)4.223 molar
D)2.938 molar
E)3.651 molar

Question 36

An aqueous solution of glycerol, C₃H₈O₃ is prepared by adding 150.0 g of glycerol to 200.0 g of water. What is the mole fraction of glycerol in the final solution?

A)0.571
B)0.429
C)0.750
D)0.872
E)0.128

Question 37

An aqueous solution of ethanol, C₂H₅OH is prepared by adding 200. g of ethanol to 50.0 g of water. What is the mole fraction of ethanol in the final solution?

A)0.200
B)0.610
C)0.390
D)0.250
E)0.800

Question 38

The vapor pressure of a solution containing a nonvolatile solute is directly proportional to the

A)mole fraction of the solvent.
B)mole fraction of the solute.
C)molality of the solvent.
D)molarity of the solvent.
E)osmotic pressure of the solute.

Question 39

When a nonvolatile solute such as ammonium sulfate is dissolved in a solvent like water, one of the observed effects is

A)a decrease in the vapor pressure of the solvent.
B)an increase in the vapor pressure of the solute.
C)an increase in the freezing point of the liquid.
D)a decrease in the boiling point of the liquid.
E)scattering of light beams by the solute particles in the solution.

Question 40

At 23.0^°C, the vapor pressure of acetonitrile, CH₃CN, is 81.0 torr while that of acetone, C₃H₆O, is 184.5 torr. What is the vapor pressure of a solution that contains 0.550 moles of acetonitrile and 0.350 moles of acetone? (Assume the mixture behaves as an ideal solution.)

A)109 torr
B)121 torr
C)130 torr
D)144 torr
E)239 torr

Question 41

During osmosis,

A)pure solvent passes through a membrane but solutes do not.
B)pure solute passes through a membrane but solvent does not.
C)pure solvent moves in one direction through the membrane while the solution moves through the membrane in the other direction.
D)pure solvent moves in one direction through the membrane while the solute moves through the membrane in the other direction.
E)pure solute moves in one direction through the membrane while the solution moves through the membrane in the other direction.

Question 42

A very dilute solution contains 116 mg of fructose (molar mass = 180.16 g mol^-1)in 1.000 liter of solution. It is placed in an osmotic membrane bladder, which is then suspended in pure water. What osmotic pressure would develop across the membrane if the temperature is 26.0°C?

A)3.36 torr
B)12.0 torr
C)151 torr
D)475 torr
E)1217 torr

Question 43

Which aqueous solution will have the highest boiling point temperature?

A)0.100 molal NiBr₂(aq)
B)0.100 molal MgSO₄(aq)
C)0.150 molal NH₄NO₃(aq)
D)0.150 molal Na₂SO₄(aq)
E)0.250 molal CH₃OH(aq)

Question 44

Which aqueous solution will have the lowest boiling point temperature?

A)0.100 molal NiBr₂(aq)
B)0.200 molal MgSO₄(aq)
C)0.150 molal NH₄NO₃(aq)
D)0.150 molal Na₂SO₄(aq)
E)0.250 molal CH₃OH(aq)

Question 45

Which solution has the highest osmotic pressure at 25°C?

A)0.200 M (NH₄)₂SO₄
B)0.200 M KClO₃
C)0.200 M C₂H₆O, ethanol
D)0.200 M NiF₂
E)0.200 M Fe(NO₃)₃

Question 46

Arrange these aqueous solutions in order of increasing boiling points:

A)C₂H₆O₂ < Mg(NO₃)₂ < LiCl
B)Mg(NO₃)₂ < LiCl < C₂H₆O₂
C)C₂H₆O₂ < LiCl < Mg(NO₃)₂
D)LiCl < C₂H₆O₂ < Mg(NO₃)₂
E)Mg(NO₃)₂ < C₂H₆O₂ < LiCl

Question 47

A dilute aqueous solution of CaCl₂ contains 0.159 grams of solute per liter of solution. It is fully dissociated. What is its osmotic pressure at 20.0^°C?Hint: CaCl₂ is an ionic compound.

A)1.79 torr
B)3.49 torr
C)26.2 torr
D)78.6 torr
E)2.65 × 10³ torr

Question 48

At 28.0°C, the vapor pressure of n-propyl mercaptan, C₃H₇SH, is 175 torr, while that of acetonitrile, CH₃CN, is 102 torr. What is the vapor pressure, at 28.0°C, of a solution made by mixing 100.0 g of C₃H₇SH and 100.0 g CH₃CN, if Raoult's Law is obeyed?

A)35.7 torr
B)128 torr
C)139 torr
D)149 torr
E)277 torr

Question 49

A molecular solute with a molar mass of 50.0 g mol^-1 is dissolved in 500 g of water and the resulting solution has a boiling point of 101.53^°C. How many grams of solute were in the solution $\Delta$ K_b = 0.512 °C m^-1

A)30.0 grams
B)75.0 grams
C)100 grams
D)125 grams
E)150 grams

Question 50

A solution contains 221 g of glycerol (C₃H₈O₃)in 600 grams of water. For the solvent, the K_f is 1.86 °C m^-1 and K_b is 0.512 °C m^-1. What should the boiling point of the solution be?

A)100.02°C
B)2.04°C
C)101.65°C
D)102.04°C
E)3.62°C

Question 51

A solution, which was made by dissolving 62.07 g of a nonelectrolyte in 500 g of water, exhibits a freezing point of -1.86°C. What is the molecular weight of this nonelectrolyte compound? For water, K_f is 1.86°C m^-1 and K_b is 0.512°C m^-1.

A)57.7 g mol^-1
B)62.07 g mol^-1
C)115 g mol^-1
D)124 g mol^-1
E)231 g mol^-1

Question 52

How many moles of the nonelectrolyte, propylene glycol (C₃H₈O₂)should be dissolved in 800.0 g of water to prepare a solution whose freezing point is -3.72°C?For water, K_f is 1.86°C m^-1 and K_b is 0.512°C m^-1.

A)1.60 moles
B)2.00 moles
C)2.50 moles
D)2.98 moles
E)4.65 moles

Question 53

Which can be used to calculate the osmotic pressure of a solution?

A)de Broglie equation
B)Tyndall factor
C)Peters equation
D)van der Waals equation
E)van't Hoff equation

Question 54

How many grams of glycerol (C₃H₈O₃, a nonelectrolyte)should be dissolved in 600 g of water to prepare a solution whose freezing point is -4.65°C? For water, K_f is 1.86°C m^-1 and K_b is 0.512 °C m^-1.

A)22.1 grams
B)93.6 grams
C)138 grams
D)384 grams
E)478 grams

Question 55

Which aqueous solution has the highest boiling point?

A)0.200 m KCl(aq)
B)0.200 m Na₂SO₄(aq)
C)0.200 m Ca(NO₃)₂(aq)
D)0.200 m C₃H₈O₃ (aq), glycerol
E)0.200 m Na₃PO₄(aq)

Question 56

A solution is made by dissolving 0.840 moles of sodium hydroxide in 300.0 g of water. If the van't Hoff factor, i, for this particular concentration is 1.70, what is the expected freezing point of this solution? K_f = 1.86 °C m^-1.

A)+0.80°C
B)-2.66°C
C)+3.06°C
D)-8.85°C
E)-9.97°C

Question 57

9.92 grams of a compound with a molar mass of 124.0 grams/mole when dissolved in 150.0 grams of water gave a solution that had a freezing point of -2.69°C. Calculate the experimental value of the van't Hoff factor. K_f = 1.86 °C m^-1.

A)1.21
B)1.45
C)1.54
D)2.69
E)2.71

Question 58

A solution is made by dissolving 1.25 moles of magnesium nitrate in 300.0 g of water. If the van't Hoff factor, i, for this particular concentration is 2.25, what is the expected freezing point of this solution? K_f = 1.86 °C m^-1.

A)-0.45°C
B)-1.57°C
C)-3.44°C
D)-5.23°C
E)-17.4°C

Question 59

An aqueous solution which is 12.00% sodium hydroxide by weight has a freezing point of ?10.40°C. What is the observed value of the van't Hoff factor, i, in this solution? K_f = 1.86 °C m^-1.

A)1.59
B)1.86
C)1.64
D)1.75
E)1.70

Question 60

Which aqueous solution should have the highest osmotic pressure?

A)0.100 molar Al(NO₃)₃
B)0.150 molar Ba(NO₃)₂
C)0.100 molar CaCl₂
D)0.150 molar NaCl
E)0.200 molar NH₃

Question 61

Below is a diagram of vapor pressure versus composition for a mixture of two liquids. The dark straight lines represent the vapor pressure of each pure liquid, while the gray curved line gives the vapor pressure of the mixture. Using this information, which of the following statements is true about the mixture?

A)The mixture is an ideal mixture that has no deviation from Raoult's Law.
B)The mixture is an ideal mixture with a positive deviation from Raoult's Law.
C)The mixture is not ideal and interactions between unlike molecules in solution are weaker than the interactions between like molecules in pure solution.
D)The mixture is not ideal and interactions between unlike molecules in solution are stronger than the interactions between like molecules in the pure solution.
E)The mixture is ideal and interactions between unlike molecules in solution are the same as the interactions between like molecules in the pure solution.

Question 62

At 28.0°C, the vapor pressure of npropyl mercaptan, C₃H₇SH, is 175 torr, while that of acetonitrile, CH₃CN, is 102 torr. What is the vapor pressure, at 28.0°C, of a solution made by mixing 120.0 g of C₃H₇SH and 80.0 g CH₃CN, if Raoult's Law is obeyed?Hint: Organizing the given information into moles and mole fraction of each component will help in solving this problem.

A)131 torr
B)135 torr
C)142 torr
D)146 torr
E)277 torr

Question 63

At 28.0^°C, the vapor pressure of n-propyl mercaptan, C₃H₇SH, is 175 torr, while that ofacetonitrile, CH₃CN, is 102 torr. What is the vapor pressure, at 28.0°C, of a solution made bymixing 80.0 g of C₃H₇SH and 120.0 g CH₃CN, if Raoult's Law is obeyed?Hint: Organizing the given information into moles and mole fraction of each component will help in solving this problem.

A)121 torr
B)131 torr
C)139 torr
D)146 torr
E)156 torr

Question 64

At 28.0°C, the vapor pressure of acetonitrile, CH₃CN, is 102.0 torr while that of acetone, C₃H₆O, is 228.9 torr, and for CS₂ the value is 378.7 torr. A three-component solution is made by adding 0.300 moles of CH₃CN and 0.400 moles of C₃H₆O to 0.350 moles of CS₂. The mixture behaves as an ideal mixture. What is the vapor pressure of the solution?Hint: Organizing the given information into moles and mole fraction of each component will help in solving this problem.

A)203 torr
B)385 torr
C)262 torr
D)275 torr
E)610 torr

Question 65

At 28.0°C, the vapor pressure of pure carbon disulfide, CS₂, is 378.7 torr, while that of acetone, C₃H₆O, is 228.9 torr. What is the vapor pressure, at 28.0°C, of a solution made by mixing 0.250 moles of carbon disulfide and 0.450 moles of acetone, if Raoult's Law is obeyed?Hint: Organizing the given information into moles and mole fraction of each component will help in solving this problem.

A)198 torr
B)228 torr
C)282 torr
D)325 torr
E)425 torr

Question 66

What is the expected freezing point of a solution that contains 25.0 g of fructose, C₆H₁₂O₆, in 250.0 g of H₂O? For water, K_f = 1.86 °C m^-1.

A)-0.10°C
B)+0.10°C
C)-0.186°C
D)+0.186°C
E)-1.03°C

Question 67

What is the freezing point of a solution that contains 20.0 g of glucose (C₆H₁₂O₆)in 100.0 g of H₂O? K_f for water is 1.86°C/m.

A)-0.206°C
B)-2.06°C
C)-1.86°C
D)+0.111°C
E)+1.11°C

Question 68

What is the normal boiling point of a solution that contains 30.0 g of glucose (C₆H₁₂O₆)in 100.0 g of H₂O? K_b for water is 0.512°C/m.

A)0.17°C
B)99.01°C
C)101.67°C
D)100.85°C
E)101.53°C

Question 69

Pure benzene, C₆H₆, has a freezing point of 5.45°C. Its freezing point depressionconstant is: K_f = 5.07 °C m^-1. A solution was made by taking 24.20 g of an unknown nonelectrolyte and dissolving it in 125.0 g of benzene. The measured freezing point of the solution was -1.65°C. Calculate the molecular weight of the unknown substance.Hint: Find molality, then moles, then molar mass, being sure to keep track of units.

A)138 g mol^-1
B)145 g mol^-1
C)258 g mol^-1
D)272 g mol^-1
E)595 g mol^-1

Question 70

Pure cyclohexane, C₆H₁₂, has a freezing point of 6.53°C. Its freezing point depression constant is: K_f = 20.0 °C m^-1. A solution was made by taking 11.40 g of an unknown nonelectrolyte and dissolving it in 150.0 g of cyclohexane. The measured freezing point of the solution was -0.78°C. Calculate the molecular weight of the unknown substance.Hint: Find molality, then moles, then molar mass, being sure to keep track of units.

A)27.8 g mol^-1
B)46.8 g mol^-1
C)208 g mol^-1
D)264 g mol^-1
E)1949 g mol^-1

Question 71

Pure cyclohexane, C₆H₁₂, has a freezing point of 6.53°C. Its freezing point depression constant is: K_f = 20.0 °C m^-1. A solution was made by taking 18.55 g of an unknown nonelectrolyte and dissolving it in 150.0 g of cyclohexane. The measured freezing point of the solution was -4.28°C. Calculate the molecular weight of the unknown substance.Hint: Find molality, then moles, then molar mass, being sure to keep track of units.

A)61.8 g mol^-1
B)66.8 g mol^-1
C)229 g mol^-1
D)578 g mol^-1
E)1099 g mol^-1

Question 72

Pure glacial acetic acid, HC₂H₃O₂, has a freezing point of 16.62°C. Its freezing point depression constant is: K_f = 3.57 °C m^-1. A solution was made by taking 9.755 g of an unknown nonelectrolyte and dissolving it in 90.50 g of glacial acetic acid. The measured freezing point of the solution was 8.64°C. Calculate the molecular weight of the unknown substance.Hint: Find molality, then moles, then molar mass, being sure to keep track of units.

A)24.4 g mol^-1
B)30.5 g mol^-1
C)45.3 g mol^-1
D)48.2 g mol^-1
E)174 g mol^-1

Question 73

Pure benzene, C₆H₆, has a freezing point of 5.45°C. Its freezing point depressionconstant is: K_f = 5.07 °C m^-1. A solution was made by taking 10.00 g of an unknown nonelectrolyte and dissolving it in 105.0 g of benzene. The measured freezing point of the solution was -1.05°C. Calculate the molecular weight of the unknown substance.Hint: Find molality, then moles, then molar mass, being sure to keep track of units.

A)74.3 g mol^-1
B)82.7 g mol^-1
C)110 g mol^-1
D)122 g mol^-1
E)460 g mol^-1

Question 74

An aqueous ethylene glycol solution being considered for use as a radiator coolant is 16.0% C₂H₆O₂ by weight. What would be the expected boiling point of this solution? For water, K_f is 1.86 °C m^-1 and K_b = 0.512 °C m^?1.Hint: convert percent by mass to molality, then find $\Delta$ T.

A)100.3°C
B)101.6°C
C)105.1°C
D)106.0°C
E)156.5°C

Question 75

Pure chloroform, CHCl₃, has a boiling point of 61.23°C. Its boiling point elevation constant, K_b, is 3.63°C m^-1. A solution was made by taking 11.25 g of an unknown nonelectrolyte and dissolving it in 115.5 g of chloroform. The measured boiling point of the solution was 65.46°C. Calculate the molecular weight of the unknown substance.Hint: Find molality, then moles, then molar mass, being sure to keep track of units.

A)83.6 g mol^-1
B)113 g mol^-1
C)114 g mol^-1
D)120 g mol^-1
E)158 g mol^-1

Question 76

Which property of a solution is not a colligative property?

A)solubility of a solute
B)freezing point depression
C)boiling point elevation
D)osmotic pressure
E)vapor pressure lowering

Question 77

An aqueous solution made by dissolving 168 mg of an unknown compound (a nonelectrolyte)in enough water to make 500.0 mL of solution, develops an osmotic pressure of 5.22 torr at a temperature of 23.5°C. What is the molecular mass of this unknown compound?Hint: Find molarity, then moles, then molar mass, being sure to keep track of units.

A)94.3 g mol^-1
B)124 g mol^-1
C)943 g mol^-1
D)1.19 × 10³ g mol^-1
E)1.57 × 10³ g mol^-1

Question 78

Which aqueous solution will have the lowest freezing point temperature?

A)0.100 molal NaBr(aq)
B)0.100 molal MgSO₄(aq)
C)0.150 molal KClO₃(aq)
D)0.150 molal MgCl₂(aq)
E)0.250 molal C₆H₁₂O₆(aq)

Question 79

A solution is prepared by mixing 0.3355 moles of NaNO₃ with 235.0 g of water. Its density is 1.0733 g mL^-1. If K_f = 1.86 °C m^-1 and the solute is completely ionized, what is the expected freezing point of the solution?Hint: be sure to classify the solute as an electrolyte or non-electrolyte.

A)2.65°C
B)2.87°C
C)-5.31°C
D)5.75°C
E)7.97°C

Question 80

Which aqueous solution will have the highest freezing point temperature?Hint: be sure to closely read the question.

A)0.100 molal MgBr₂(aq)
B)0.100 molal MgSO₄(aq)
C)0.150 molal KClO₃(aq)
D)0.150 molal MgCl₂(aq)
E)0.250 molal C₆H₁₂O₆(aq)