Deck 17: Properties of Solutions

Question 1

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.

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

Answer 1

8.56 m

Question 2

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?

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

Answer 2

0.207

Question 3

How many milliliters of 12.4 M HNO₃ are needed to prepare 360.6 mL of 0.20 M HNO₃?

A) 2.2 * 10¹ mL
B) 0.349 mL
C) 0.034 mL
D) 5.8 mL
E) 35 mL

Answer 3

5.8 mL

Question 4

Which of the following concentration measures will change in value as the temperature of a solution changes?

A) mole fraction
B) mass percent
C) molarity
D) molality
E) all of these

Question 5

An aqueous solution of a compound with a molar mass of 34.02 g/mol is 25.5% by mass and has a density of 1.19 g/cm³. What is the molarity of the solution?

A) 8.92 M
B) 7.50 M
C) 1.37 M
D) 0.000892 M
E) 6.30 M

Question 6

What is the mole percent of ethanol (C₂H₅OH) in the 180 proof vodka, which consists of 71.0 g of ethanol for every 10.0 g of water present?

A) 87.7%
B) 71.0%
C) 73.5%
D) 26.5%
E) 22.1%

Question 7

The term proof is defined as twice the percent by volume of pure ethanol in solution. Thus, a solution that is 95% (by volume) ethanol is 190 proof. What is the molarity of ethanol in a 92 proof ethanol/water solution?

A) 0.46 M
B) 0.80 M
C) 17 M
D) 0.92 M
E) 8.0 M

Question 8

A solution is composed of two liquids, A and B. For every 2.66 mol of A, there are 6.86 mol of B. What is the mole fraction of liquid A in the solution?

A) 0.721
B) 0.612
C) 0.388
D) 0.279
E) 0.633

Question 9

What is the molality of a solution of 39.8 g of ethanol (CH₃CH₂OH) in 441 mL of water if the density of water is 1.0 g/mL?

A) 90.2 m
B) 1.80 m
C) 1.96 m
D) 0.0341 m
E) 0.0353 m

Question 10

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

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

Question 11

A solution containing 100.0 g of NaCl per liter has a density of 1.095 g/mL. What is the molality of the solution?

A) 0.5873 m
B) 1.711 m
C) 1.720 m
D) 0.5844 m
E) none of these

Question 12

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

Question 13

When 271.0 mL of 0.828 M HCl is diluted with 161.6 mL of water, the molarity of the solution (assuming the volumes are additive) is

A) 0.519 M.
B) 0.111 M.
C) 0.00191 M.
D) 0.309 M.
E) 1.39 M.

Question 14

A solution is made of 173.0 g of methanol (CH₃OH) in 169.0 g of water. What is the mole fraction of methanol?

A) 0.0158
B) 0.506
C) 0.635
D) 0.594
E) 0.365

Question 15

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

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 16

Calculate the molality of a solution containing 21.0 g of C₆H₁₂O₆ in 271.0 mL of water (assume a density of 1.00 g/mL).

A) 0.399 m
B) 0.0719 m
C) 0.000430 m
D) 0.430 m
E) 0.00768 m

Question 17

An aqueous solution contains 144.0 g of NaCl per liter. What is the molarity of the solution?

A) 2.879 M
B) 2.464 M
C) 0.1682 M
D) 0.1440 M
E) 2.154 M

Question 18

An aqueous solution contains 48.6 g of KNO₃ in 290.6 mL of solution. What is the molarity of the solution?

A) 0.140 M KNO₃
B) 0.167 M KNO₃
C) 1.65 M KNO₃
D) 0.00716 M KNO₃
E) 0.0591 M KNO₃

Question 19

Rank the following compounds according to increasing solubility in water.
I.CH₃-CH₂-CH₂-CH₃
II.CH₃-CH₂-O-CH₂-CH₃
III. CH₃-CH₂-OH
IV. CH₃-OH

A) I < II < IV < III
B) I < III < IV < II
C) I < II < III < IV
D) III < IV < II < I
E) None is correct.

Question 20

When 200.0 mL of 0.200 M H₂SO₄ is diluted with 155.0 mL of water, what is the molarity of the solution?

A) 0.258 M
B) 0.155 M
C) 0.124 M
D) 0.113 M
E) none of these

Question 21

Which of the following statements is(are) true?

A) The rate of dissolution of a solid in a liquid always increases with increasing temperature.
B) The solubility of a solid in a liquid always increases with increasing temperature.
C) According to Henry's law, the amount of gas dissolved in a solution is directly proportional to the pressure of the gas above the liquid.
D) Two of these statements are true.
E) All of these statements are true.

Question 22

Which of the following chemical or physical changes is an endothermic process?

A) the mixing of sulfuric acid and water
B) the freezing of water
C) the evaporation of water
D) the combustion of gasoline
E) none of these

Question 23

A salt solution sits in an open beaker. Assuming constant temperature and pressure, the vapor pressure of the solution

A) stays the same over time.
B) We need to know which salt is in the solution to answer this.
C) increases over time.
D) We need to know the temperature and pressure to answer this.
E) decreases over time.

Question 24

A liquid-liquid solution is called an ideal solution if
I. it obeys PV = nRT.
II. it obeys Raoult's law.
III. solute-solute, solvent-solvent, and solute-solvent interactions are very similar.
IV. solute-solute, solvent-solvent, and solute-solvent interactions are quite different.

A) II, IV
B) II, III
C) I, II
D) I, II, III
E) I, II, IV

Question 25

At a given temperature, the vapor pressure of heptane is 92.0 torr and the vapor pressure of octane is 31.2 torr. Assuming ideal behavior, what is the vapor pressure of a solution that contains three times as many moles of octane as heptane?

A) 87.3 torr
B) 52.4 torr
C) 76.8 torr
D) 46.4 torr
E) none of these

Question 26

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

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 27

Predict the deviation from Raoult's law when two liquids are mixed and the heat of the solution is small.

A) negative deviation
B) relatively ideal (small or zero deviation)
C) positive deviation

Question 28

The boiling point of pure benzene at 760. torr is 80.1°C. What is the vapor pressure of benzene over a solution containing 4.60 mol of nonvolatile hydrocarbon and 11.60 mol of benzene at 80.1°C?

A) 6.43*10² torr
B) 5.44 * 10² torr
C) 2.16 *10² torr
D) 7.60 * 10² torr
E) 1.51 * 10² torr

Question 29

If a solution exhibits a negative deviation from Raoult's law, the vapor pressure of the solution is __________ what would be expected ideally.

A) equal to
B) greater than
C) less than

Question 30

A 54.4-g sample of glucose (a nondissociated, nonvolatile solute with the formula C₆H₁₂O₆) is dissolved in 154.4 g of water. What is the vapor pressure of this solution at 100°C?

A) 734 torr
B) 562 torr
C) 25.9 torr
D) 760 torr
E) 198 torr

Question 31

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

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

Question 32

Which statement about hydrogen bonding is true?

A) Hydrogen bonding arises from the dipole moment created by the unequal sharing of electrons in certain covalent bonds within a molecule.
B) Hydrogen bonding of solvent molecules with a solute will not affect the solubility of the solute.
C) The hydrogen-bonding capabilities of water molecules cause CH₃CH₂CH₂CH₃ to be more soluble in water than is CH₃OH.
D) Hydrogen-bonding interactions between molecules are stronger than the covalent bonds within the molecule.
E) Hydrogen bonding is the intermolecular attractive forces between two hydrogen atoms in solution.

Question 33

When 0.800 g of NH₄NO₃ was added to 150.0 g of water in a styrofoam cup, the temperature dropped by 0.413°C. The heat capacity of H₂O is 4.18 J/g°C. Assume the specific heat of the solution equals that of pure H₂O and that the calorimeter neither absorbs nor leaks heat. What is the molar heat of solution of solid NH₄NO₃?

A) +260. J/mol
B) -2.60 kJ/mol
C) +2.60 kJ/mol
D) +26.0 kJ/mol
E) none of these

Question 34

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.

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

Question 35

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) relatively ideal
B) positive deviation
C) negative deviation

Question 36

Predict the deviation from Raoult's law when two liquids are mixed and the heat of the solution is large and the reaction exothermic.

A) positive deviation
B) relatively ideal (small or zero deviation)
C) negative deviation

Question 37

The solubility of O₂ in water is 0.590 g/L at an oxygen pressure of 15 atm. What is the Henry's law constant for O₂ (in units of L atm/mol)?

A) 3.93 *10^-3
B) 1.23 * 10^-3
C) 8.14 *10²
D) 1.26
E) None of the above is within 5% of the correct answer.

Question 38

Solid KF has a lattice energy of -804 kJ/mol and a heat of solution (in water) of -15 kJ/mol. RbF has a lattice energy of -768 kJ/mol and a heat of solution (in water) of -24 kJ/mol. Which salt forms stronger attractions with water?

A) They form equally strong attractions with water, because they both have negative heats of mixing.
B) KF, because it has a more exothermic lattice energy
C) RbF, because it has a more negative heat of hydration
D) KF, because it has a more negative heat of hydration
E) RbF, because it has a less exothermic lattice energy

Question 39

Predict the deviation from Raoult's law when two liquids are mixed and the heat of the solution is large and the reaction endothermic.

A) positive deviation
B) relatively ideal (small or zero deviation)
C) negative deviation

Question 40

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?
acetone (C₃H₆O) and water

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

Question 41

To calculate the freezing point of an ideal dilute solution of a single, nondissociating solute in a solvent, the minimum information one must know is
I.The molality (of the solute).
II.The molality (of the solute) and the freezing-point-depression constant of the solvent.
III.The freezing point of the pure solvent.
IV.The molecular weight of the solute.
V.The weight of the solvent.

A) II, III only
B) II only
C) II, III, IV
D) II, III, V
E) I only

Question 42

The molar mass of a solid as determined by freezing-point depression is 10% higher than the true molar mass. Which of the following experimental errors could not account for this discrepancy?

A) Before the solution was prepared, the container was rinsed with solvent and not dried.
B) Some solid was left on the weighing paper.
C) Not all the solid was dissolved.
D) The solid dissociated slightly into two particles when it dissolved.
E) More than the recorded amount of solvent was pipetted into the solution.

Question 43

The freezing point (T_f) for t-butanol is 25.50°C, and K_f is 9.1°C/m. Usually t-butanol absorbs water on exposure to the air. If the freezing point of a 13.9-g sample of t-butanol is measured as 24.91°C, how many grams of water are present in the sample?

A) 7.0 g
B) 0.016 g
C) 0.21 g
D) 0.021 g
E) 0.76 g

Question 44

When a 18.4-g sample of an unknown compound is dissolved in 522.0 g of benzene, the freezing point of the resulting solution of 3.82°C. The freezing point of pure benzene is 5.48°C, and K_f for benzene is 5.12°C/m. Calculate the molar mass of the unknown compound.

A) 9.20 * 10³ g/mol
B) 4.72 *10¹ g/mol
C) 8.85 * 10² g/mol
D) 2.96 * 10¹ g/mol
E) 1.09 * 10² g/mol

Question 45

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

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 46

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?

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 47

Adding salt to water decreases the freezing point of the water because it lowers the vapor pressure of the ice.

Question 48

Using the data below, calculate the vapor pressure of benzene 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) 148 torr
B) 68.0 torr
C) 172 torr
D) 125 torr
E) none of these

Question 49

At a given temperature, you have a mixture of benzene (P_vap = 745 torr) and toluene (P_vap = 290 torr). The mole fraction of benzene in the solution is 0.590. Assuming ideal behavior, calculate the mole fraction of toluene in the vapor above the solution.

A) 0.778
B) 0.641
C) 0.355
D) 0.213
E) 0.590

Question 50

Liquid A has vapor pressure x. Liquid B has vapor pressure y, and x > y. What is the mole fraction of A in the liquid mixture if the vapor above the solution is 50% A?

A) y/(2x + 2y)
B) y/(x + y)
C) x/(2x + 2y)
D) x/(x + y)
E) none of these

Question 51

A 5.96-g sample of a compound is dissolved in 222.0 g of benzene. The freezing point of this solution is 1.06°C below that of pure benzene. What is the molar mass of this compound? (Note: K_f for benzene = 5.12°C/m.)

A) 1.30* 10² g/mol
B) 2.85 *10¹ g/mol
C) 1.80 * 10² g/mol
D) 6.39 * 10³ g/mol
E) 5.56 *10² g/mol

Question 52

Liquid A has vapor pressure x. Liquid B has vapor pressure y, and x > y. What is the mole fraction of A in the liquid mixture if the vapor above the solution is 30% A?

A) 0.7x/(0.7x + 0.3y)
B) 0.3x/(0.3x + 0.7y)
C) 0.7y/(0.3x + 0.7y)
D) 0.3y/(0.7x + 0.3y)
E) none of these

Question 53

The molal freezing-point depression constants for benzene and water are 5.12 and 1.86, respectively. When 4.6 g of formic acid (HCOOH) is dissolved in 1.0 kg of benzene, the freezing point is depressed by 0.26°C. When the same amount of formic acid is dissolved in 1.0 kg of water, the freezing point is lowered by 0.19°C. To explain these results, we must assume that

A) formic acid is monomeric in benzene and associated in water.
B) formic acid is associated in benzene and monomeric in water.
C) formic acid is monomeric in benzene and dissociated in water.
D) formic acid is dissociated in benzene and monomeric in water.

Question 54

What is the boiling-point change for a solution containing 0.360 mol of naphthalene (a nonvolatile, nonionizing compound) in 258.0 g of liquid benzene? (K_b = 2.53°C/m for benzene)

A) 1.81°C
B) 8.60°C
C) 0.552°C
D) 0.235°C
E) 3.53°C

Question 55

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 octane (C₈H₁₈)

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

Question 56

A solution contains 1 mol of liquid A and 3 mol of liquid B. The vapor pressure of this solution is 314 torr at 25°C. At 25°C, the vapor pressure of liquid A is 265 torr and the vapor pressure of liquid B is 355 torr. Which of the following is true?

A) This solution exhibits a positive deviation from Raoult's law.
B) This solution is ideal.
C) This solution exhibits a negative deviation from Raoult's law.

Question 57

Pentane (C₅H₁₂) and hexane (C₆H₁₄) form an ideal solution. The vapor pressures of pentane and hexane at 25° C are 511 torr and 150 torr, respectively. The mole fraction of hexane in a pentane-hexane solution is 0.50. Calculate the mole fraction of pentane in the vapor that is in equilibrium at 25°C with this solution.

A) 0.23
B) 0.77
C) 0.89
D) 0.50
E) none of these

Question 58

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

Question 59

When a 1.50-g sample of glutamic acid is dissolved in 100.0 g of H₂O, the resulting solution freezes at -0.190°C. K_f for H₂O is 1.86°C/m. The molar mass of glutamic acid is

A) 28.0 g/mol
B) 147 g/mol
C) 1.50 g/mol
D) 189 g/mol
E) 14.7 g/mol

Question 60

At a given temperature, you have a mixture of benzene (vapor pressure of pure benzene = 745 torr) and toluene (vapor pressure of pure toluene = 290 torr). The mole fraction of benzene in the vapor above the solution is 0.590. Assuming ideal behavior, calculate the mole fraction of toluene in the solution.

A) 0.778
B) 0.359
C) 0.213
D) 0.590
E) 0.641

Question 61

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

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 62

How many moles of methanol, CH₃OH, dissolved in 450.0 g of water are needed to make a 2.500 m solution?

Question 63

You use 2.0 g of solid MX to prepare a saturated solution in 250. g of water. You find the freezing point to be -0.028°C. Calculate K_sp for the solid.

A) 2.2 * 10^-4
B) 5.6 * 10^-5
C) 1.4 *10^-5
D) 3.5* 10^-6
E) none of these

Question 64

A 5.00-g sample of a compound is dissolved in enough water to form 100.0 mL of solution. This solution has an osmotic pressure of 25 torr at 25°C. If it is assumed that each molecule of the solute dissociates into two particles (in this solvent), what is the molar mass of this solute?

A) 18,600 g/mol
B) 37,200 g/mol
C) 74,300 g/mol
D) 1560 g/mol
E) none of these

Question 65

You have a 10.40-g mixture of table sugar (C₁₂H₂₂O₁₁) and table salt (NaCl). When this mixture is dissolved in 150. g of water, the freezing point is found to be -2.24°C. Calculate the percent by mass of sugar in the original mixture. (Assume that the NaCl is completely dissociated.)

A) 61.0%
B) 53.8%
C) 46.2%
D) 39.0%
E) none of these

Question 66

Polyethylene is a synthetic polymer or plastic with many uses. 1.40 g of a polyethylene sample was dissolved in enough benzene to make 100. mL of solution, and the osmotic pressure was found to be 1.86 torr at 25°C. What is the molar mass of the polyethylene?

A) 3.39 * 10⁶ g/mol
B) 1.19 *10⁴ g/mol
C) 1.06 * 10⁸ g/mol
D) 5720 g/mol
E) 1.40 *10⁵ g/mol

Question 67

The destruction of a colloid is called

A) denaturation.
B) reconfiguration.
C) coagulation.
D) degeneration.
E) none of these

Question 68

When a nonvolatile solute is added to a volatile solvent, the solution vapor pressure __________, the boiling point __________, the freezing point __________, and the osmotic pressure across a semipermeable membrane __________.

A) decreases, decreases, increases, decreases
B) increases, decreases, increases, decreases
C) decreases, increases, decreases, increases
D) increases, increases, decreases, increases
E) decreases, increases, decreases, decreases

Question 69

The solubility of the salt M_xA_y is 1.0 *10^-2 mol/L at 25°C. The osmotic pressure exhibited by a solution saturated with M_xA_y at 25°C is 1.22 atm. Determine the values of x and y by assuming ideal behavior.

A) x = 1, y =3
B) x = 2, y = 5
C) x = 1, y = 1
D) x = 2, y = 3
E) none of these

Question 70

A cucumber is placed in a concentrated salt solution. What is most likely to happen?

A) Salt will precipitate out.
B) Water will flow from the solution to the cucumber.
C) Salt will flow into the cucumber.
D) Water will flow from the cucumber to the solution.
E) No change will occur.

Question 71

What is the expected osmotic pressure, in torr, of a 0.0100 M solution of NaCl in water at 25°C?

A) 186 torr
B) 0.245 torr
C) 372 torr
D) 15.6 torr
E) none of these

Question 72

Thyroxine, an important hormone that controls the rate of metabolism in the body, can be isolated from the thyroid gland. If 0.455 g of thyroxine is dissolved in 10.0 g of benzene, the freezing point of the solution is 5.144°C. Pure benzene freezes at 5.444°C and has a value for the molal freezing-point-depression constant of K_f of 5.12°C/m. What is the molar mass of thyroxine?

A) 2330 g/mol
B) 285 g/mol
C) 777 g/mol
D) 3760 g/mol
E) 777,000 g/mol

Question 73

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).

A) 8.37 * 10³ torr
B) 2.71 * 10⁴ torr
C) 2.79 *10³ torr
D) 3.52*10^-1 torr
E) 8.03 *10² torr

Question 74

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

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

Question 75

What is the molality of an HCl solution made by dissolving 150.0 g of HCl in 450.0 g of water?

Question 76

A 0.2 molar solution of a solute X, in benzene, displays an osmotic pressure given by the formulaII = (0.1)RT. Which of the following is most likely to be the case?

A) X exists in benzene as X₂.
B) X exists in benzene as X.
C) X exists in benzene dissociated into two particles.
D) This solution strongly deviates from ideal behavior.
E) None of these explanations is plausible.

Question 77

Which of the following is an emulsion?

A) fog
B) paint
C) whipped cream
D) smoke
E) milk

Question 78

When 0.014 mol of a weak acid HA is dissolved in enough water to make 1.0 L of solution, [H⁺] is 1.8 *10^-3 M. Calculate the freezing point of this solution. Assume that the molarity concentration is equal to the molality concentration, and assume ideal behavior. K_f (H₂O) is 1.86°C kg/mol.

A) -0.058°C
B) -0.029°C
C) -0.026°C
D) +0.029°C
E) +0.026°C

Question 79

Calculate the molarity of the solution made by dissolving 100.0 g of calcium nitrate in 450.0 mL of aqueous solution.

Question 80

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

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