Question 1

We can predict the solubility of a compound by looking at the sign of the enthalpy of solution.

Accepted Answer

A) True 
 B)False

Question 2

A chemist is given a white solid that is suspected of being pure cocaine (molar mass = 303.35 g/mol). When 1.22 g of the solid is dissolved in 15.60 g of benzene, the freezing point is lowered by 1.32°C. The molar mass is calculated from these data to be 303 g. Assuming the following uncertainties, can the chemist be sure the substance is not codeine (molar mass 299.36)? K_f for benzene is 5.12°C/m. Uncertainties Mass of solid = ±0.01 g Mass of benzene = ±0.01 g $\Delta$T (freezing-point lowering) = ±0.04°C K_f = ±0.01 Support your answer with calculations.

Accepted Answer

The answer of A chemist is given a white solid...

Question 3

The phrase "a solid dissolved in a gas" describes a(n)

Accepted Answer

A)  aerosol. 
B)  emulsion. 
C)  foam. 
D)  sol. 
E)  none of these

Question 4

Calculate the mole fraction of C₁₂H₂₂O₁₁ in a solution prepared by dissolving 250.0 g of C₁₂H₂₂O₁₁ in 1.00 kg of H₂O.

Accepted Answer

The answer of Calculate the mole fraction of C₁₂H₂₂O₁₁ in...

Question 5

When 1 mol of a nonvolatile solvent-nondissociating substance is dissolved in 3 mol of solvent, the ratio of vapor pressure of the solution to that of the pure solvent (at the same temperature) is approximately

Accepted Answer

A)  2/3. 
B)  3/4. 
C)  1/4. 
D)  1/3. 
E)  none of these

Question 6

Consider a solution containing liquids A and B where the mole fraction of B is 0.60. Assuming ideality, calculate the mole fractions of A and B in the vapor at equilibrium with this solution at 25°C. (The vapor pressures of pure liquid A and pure liquid B at 25°C are 200. torr and 400. torr, respectively.)

Accepted Answer

The answer of Consider a solution containing liquids A and...

Question 7

For each of the following solutions, would you expect it with respect to Raoult's law) to be relatively ideal, to show a positive deviation, or to show a negative deviation?
-hexane (C6H14) and chloroform (CHCl3)

Accepted Answer

A)  relatively ideal 
B)  positive deviation 
C)  negative deviation

Question 8

A solution of two liquids, A and B, shows negative deviation from Raoult's law. This means that

Accepted Answer

A)  the molecules of A hinder the strong interaction between B molecules. 
B)  molecules of A interact strongly with other A-type molecules. 
C)  molecules of A interact more strongly with B than with A or and more strongly than B with B. 
D)  the two liquids have a positive heat of solution. 
E)  molecules of A interact weakly, if at all, with B molecules.

Question 9

A solute added to a solvent raises the boiling point of the solution because

Accepted Answer

A)  the solute particles lower the solvent's vapor pressure, thus requiring a higher temperature to cause boiling. 
B)  the temperature to cause boiling must be great enough to boil not only the solvent but also the solute. 
C)  the solute increases the volume of the solution, and an increase in volume requires an increase in the temperature to reach the boiling point (derived from PV = nRT). 
D)  the solute particles raise the solvent's vapor pressure, thus requiring a higher temperature to cause boiling. 
E)  Two of the above are correct.

Question 10

Consider pure water separated from an aqueous sugar solution by a semipermeable membrane, which allows water to pass freely but not sugar. After some time has elapsed, the concentration of sugar solution

Accepted Answer

A)  will have increased. 
B)  will be the same on both sides of the membrane. 
C)  might have increased or decreased, depending on other factors. 
D)  will have decreased. 
E)  will not have changed.

Question 11

The osmotic pressure of a 0.0100 M solution of NaCl in water at 25°C is found to be different from 372 torr because

Accepted Answer

A)  osmotic pressures are hard to measure. 
B)  Na+ and Cl- ions are strongly hydrated. 
C)  NaCl does not dissociate in water. 
D)  Na+ and Cl- ions can form ion pairs. 
E)  none of these

Question 12

Which of the following will cause the calculated molar mass of a compound determined by the freezing-point depression method to be greater than the true molar mass?

Accepted Answer

A)  While adding the solute, the technician spilled some of it on the lab bench. 
B)  Water gets into the solvent after the freezing point of the pure solvent is determined. 
C)  Some of the solute molecules break apart. 
D)  The mass of solvent is smaller than determined from the weighing. 
E)  all of these

Question 13

Calculate the molality of C2H5OH in a water solution that is prepared by mixing 50.0 mL of C2H5OH with 100.0 mL of H2O at 20°C. The density of the C2H5OH is 0.789 g/mL at 20°C.

Accepted Answer

A)  1.24 m 
B)  0.086 m 
C)  8.56 m 
D)  0.094 m 
E)  none of these

Question 14

An aqueous solution contains 42.4 g of propanol (C3H7OH) in 113.6 g of solution. What is the mole fraction of propanol?

Accepted Answer

A)  0.151 
B)  0.272 
C)  0.217 
D)  0.179 
E)  0.849

Question 15

You have at your disposal 3 1-pound bags of various pure salts that dissolve readily in water. You can add one of the bags to a 55 gallon barrel of water. Which bag should you use to lower the freezing point by the greatest amount? (1 lb. = 0.454 kg)

Accepted Answer

A)  Bag of KCl 
B)  Bag of MgCl2 
C)  Bag of Ba(NO3)2 
D)  Either B or C

Question 16

In a 0.1 molar solution of NaCl in water, which of the following will be closest to 0.1?

Accepted Answer

A)  the molality of NaCl 
B)  the mass percent of NaCl 
C)  the mole fraction of NaCl 
D)  the mass fraction of NaCl 
E)  All of these are about 0.1.

Question 17

Using the data below, calculate the vapor pressure of chloroform over a chloroform-benzene solution at 25°C, which contains 50.0 g of CHCl3 and 50.0 g of C6H6. Assume that the solution behaves ideally.

Accepted Answer

A)  68.0 torr 
B)  148 torr 
C)  125 torr 
D)  172 torr 
E)  none of these

Question 18

A 50.0-g sample of ethyl alcohol (C2H5OH) is dissolved in 75.0 g of water. What is the mole fraction of ethyl alcohol?

Accepted Answer

A)  0.342 
B)  0.667 
C)  0.414 
D)  0.207 
E)  none of these

Question 19

Calculate the osmotic pressure (in torr) of 5.50 L of an aqueous 0.148 M solution at 29°C if the solute concerned is totally ionized into three ions (for example, it could be Na2SO4 or MgCl2).

Accepted Answer

A)  8.37 F1F1F1S1F1F1F10 103 torr 
B)  2.71 F1F1F1S1F1F1F10 104 torr 
C)  2.79 F1F1F1S1F1F1F10 103 torr 
D)  3.52 F1F1F1S1F1F1F10 10-1 torr 
E)  8.03 F1F1F1S1F1F1F10 102 torr

Question 20

The lattice energy of NaI is -686 kJ/mol, and its heat of solution is -7.6 kJ/mol. Calculate the hydration of energy of NaI(s) in kJ/mol.

Accepted Answer

A)  -678 
B)  +694 
C)  -694 
D)  +678 
E)  +15.2

Exam 17: Properties of Solutions

We can predict the solubility of a compound by looking at the sign of the enthalpy of solution.

The phrase "a solid dissolved in a gas" describes a(n)

Calculate the mole fraction of C₁₂H₂₂O₁₁ in a solution prepared by dissolving 250.0 g of C₁₂H₂₂O₁₁ in 1.00 kg of H₂O.

When 1 mol of a nonvolatile solvent-nondissociating substance is dissolved in 3 mol of solvent, the ratio of vapor pressure of the solution to that of the pure solvent (at the same temperature) is approximately

For each of the following solutions, would you expect it with respect to Raoult's law) to be relatively ideal, to show a positive deviation, or to show a negative deviation? -hexane (C₆H₁₄) and chloroform (CHCl₃)

A solution of two liquids, A and B, shows negative deviation from Raoult's law. This means that

A solute added to a solvent raises the boiling point of the solution because

Consider pure water separated from an aqueous sugar solution by a semipermeable membrane, which allows water to pass freely but not sugar. After some time has elapsed, the concentration of sugar solution

The osmotic pressure of a 0.0100 M solution of NaCl in water at 25°C is found to be different from 372 torr because

Which of the following will cause the calculated molar mass of a compound determined by the freezing-point depression method to be greater than the true molar mass?

Calculate the molality of C₂H₅OH in a water solution that is prepared by mixing 50.0 mL of C₂H₅OH with 100.0 mL of H₂O at 20°C. The density of the C₂H₅OH is 0.789 g/mL at 20°C.

An aqueous solution contains 42.4 g of propanol (C₃H₇OH) in 113.6 g of solution. What is the mole fraction of propanol?

You have at your disposal 3 1-pound bags of various pure salts that dissolve readily in water. You can add one of the bags to a 55 gallon barrel of water. Which bag should you use to lower the freezing point by the greatest amount? (1 lb. = 0.454 kg)

In a 0.1 molar solution of NaCl in water, which of the following will be closest to 0.1?

Using the data below, calculate the vapor pressure of chloroform over a chloroform-benzene solution at 25°C, which contains 50.0 g of CHCl₃ and 50.0 g of C₆H₆. Assume that the solution behaves ideally.

A 50.0-g sample of ethyl alcohol (C₂H₅OH) is dissolved in 75.0 g of water. What is the mole fraction of ethyl alcohol?

Calculate the osmotic pressure (in torr) of 5.50 L of an aqueous 0.148 M solution at 29°C if the solute concerned is totally ionized into three ions (for example, it could be Na₂SO₄ or MgCl₂) .

The lattice energy of NaI is -686 kJ/mol, and its heat of solution is -7.6 kJ/mol. Calculate the hydration of energy of NaI(s) in kJ/mol.

Exam 17: Properties of Solutions

We can predict the solubility of a compound by looking at the sign of the enthalpy of solution.

The phrase "a solid dissolved in a gas" describes a(n)

Calculate the mole fraction of C12H22O11 in a solution prepared by dissolving 250.0 g of C12H22O11 in 1.00 kg of H2O.

When 1 mol of a nonvolatile solvent-nondissociating substance is dissolved in 3 mol of solvent, the ratio of vapor pressure of the solution to that of the pure solvent (at the same temperature) is approximately

For each of the following solutions, would you expect it with respect to Raoult's law) to be relatively ideal, to show a positive deviation, or to show a negative deviation? -hexane (C6H14) and chloroform (CHCl3)

A solution of two liquids, A and B, shows negative deviation from Raoult's law. This means that

A solute added to a solvent raises the boiling point of the solution because

Consider pure water separated from an aqueous sugar solution by a semipermeable membrane, which allows water to pass freely but not sugar. After some time has elapsed, the concentration of sugar solution

The osmotic pressure of a 0.0100 M solution of NaCl in water at 25°C is found to be different from 372 torr because

Which of the following will cause the calculated molar mass of a compound determined by the freezing-point depression method to be greater than the true molar mass?

Calculate the molality of C2H5OH in a water solution that is prepared by mixing 50.0 mL of C2H5OH with 100.0 mL of H2O at 20°C. The density of the C2H5OH is 0.789 g/mL at 20°C.

An aqueous solution contains 42.4 g of propanol (C3H7OH) in 113.6 g of solution. What is the mole fraction of propanol?

You have at your disposal 3 1-pound bags of various pure salts that dissolve readily in water. You can add one of the bags to a 55 gallon barrel of water. Which bag should you use to lower the freezing point by the greatest amount? (1 lb. = 0.454 kg)

In a 0.1 molar solution of NaCl in water, which of the following will be closest to 0.1?

Using the data below, calculate the vapor pressure of chloroform over a chloroform-benzene solution at 25°C, which contains 50.0 g of CHCl3 and 50.0 g of C6H6. Assume that the solution behaves ideally.

A 50.0-g sample of ethyl alcohol (C2H5OH) is dissolved in 75.0 g of water. What is the mole fraction of ethyl alcohol?

Calculate the osmotic pressure (in torr) of 5.50 L of an aqueous 0.148 M solution at 29°C if the solute concerned is totally ionized into three ions (for example, it could be Na2SO4 or MgCl2) .

The lattice energy of NaI is -686 kJ/mol, and its heat of solution is -7.6 kJ/mol. Calculate the hydration of energy of NaI(s) in kJ/mol.

Calculate the mole fraction of C₁₂H₂₂O₁₁ in a solution prepared by dissolving 250.0 g of C₁₂H₂₂O₁₁ in 1.00 kg of H₂O.

For each of the following solutions, would you expect it with respect to Raoult's law) to be relatively ideal, to show a positive deviation, or to show a negative deviation? -hexane (C₆H₁₄) and chloroform (CHCl₃)

Calculate the molality of C₂H₅OH in a water solution that is prepared by mixing 50.0 mL of C₂H₅OH with 100.0 mL of H₂O at 20°C. The density of the C₂H₅OH is 0.789 g/mL at 20°C.

An aqueous solution contains 42.4 g of propanol (C₃H₇OH) in 113.6 g of solution. What is the mole fraction of propanol?

Using the data below, calculate the vapor pressure of chloroform over a chloroform-benzene solution at 25°C, which contains 50.0 g of CHCl₃ and 50.0 g of C₆H₆. Assume that the solution behaves ideally.

A 50.0-g sample of ethyl alcohol (C₂H₅OH) is dissolved in 75.0 g of water. What is the mole fraction of ethyl alcohol?

Calculate the osmotic pressure (in torr) of 5.50 L of an aqueous 0.148 M solution at 29°C if the solute concerned is totally ionized into three ions (for example, it could be Na₂SO₄ or MgCl₂) .