Deck 10: Intermolecular Forces: The Uniqueness of Water

Question 1

A hydration sphere forms around an ion in aqueous solution due to ________

A) ion-dipole interactions.
B) ion-hydrogen-bonding interactions.
C) dispersion forces.
D) dipole-dipole interactions.
E) ion-induced dipole interactions.

Answer 1

ion-dipole interactions.

Question 2

Which of the following polar compounds is likely to have the highest boiling point?

A) CH₃OCH₃
B) CH₃CH₂OH
C) (CH₃)₂CO
D) H₂CO
E) CO

Answer 2

CH₃CH₂OH

Question 3

Which of the following compounds will have the strongest dipole-dipole interactions between its molecules?

A) CF₄
B) CH₄
C) CH₃F
D) CH₂F₂
E) CH₃Cl

Answer 3

CH₂F₂

Question 4

For a molecule to exhibit dipole-dipole interactions, it must ________

A) have a temporary dipole moment.
B) have a hydrogen bound to an oxygen, nitrogen, or fluorine.
C) have a permanent dipole moment.
D) be an ion.
E) have 3 or more atoms.

Question 5

Which of the following will require the greatest energy input to separate the ions?

A) MgI₂
B) MgF₂
C) MgCl₂
D) MgBr₂
E) NaCl

Question 6

When sodium chloride dissolves in water, how do the water molecules orient around the ions?

A) Water molecules are randomly oriented around the ions.
B) The hydrogen atoms point toward both the sodium and the chloride.
C) The oxygen atoms point toward both the sodium and the chloride.
D) Around sodium the hydrogen atoms point toward the sodium, and around chloride the oxygen atoms point toward the chloride.
E) Around sodium the oxygen atoms point toward the sodium, and around chloride the hydrogen atoms point toward the chloride.

Question 7

Coulomb's law states that the energy of attraction between ions depends ________

A) only on the charge of the cation.
B) only on the charge of the anion.
C) directly on the distance between the ions.
D) on the charges of both ions.
E) on the temperature.

Question 8

Based on their boiling points, which of the following compounds has the largest dipole-dipole interaction?

A) propane (231 K)
B) dimethyl ether (248 K)
C) acetonitrile (355 K)
D) methyl chloride (249 K)
E) butane (135 K)

Question 9

Ion-dipole forces always require

A) an ion and a water molecule.
B) a cation and a water molecule.
C) an anion and a polar molecule.
D) an ion and a polar molecule.
E) a polar and a nonpolar molecule.

Question 10

Rank the following compounds in order of increasing attraction between their ions: KBr, SrBr₂, and CsBr.

A) CsBr < KBr < SrBr₂
B) SrBr₂ < CsBr < KBr
C) KBr < SrBr₂ < CsBr
D) CsBr < SrBr₂ < KBr
E) SrBr₂ < KBr < CsBr

Question 11

Predict which of the following ionic compounds has the highest melting point.

A) NaF
B) KCl
C) RbCl
D) BeF₂
E) NaCl

Question 12

Arrange the three ionic compounds sodium chloride, magnesium chloride, and aluminum chloride in order of increasing melting point.

A) NaCl < MgCl₂ < AlCl₃
B) MgCl₂ < NaCl < AlCl₃
C) AlCl₃ < MgCl₂ < NaCl
D) AlCl₃ < NaCl < MgCl₂
E) NaCl < AlCl₃ < MgCl₂

Question 13

Ion interaction energies are determined by Coulomb's law: $$E = \left( 2.31 \times 10 ^ { - 19 } J \cdot n m \right) \left( \frac { Q _ { 1 } Q _ { 2 } } { d } \right)$$ Determine the energy of potassium chloride if the radius of the potassium ion is 133 pm and that of the chloride ion is 181 pm.

A) -7.36 * 10^-19 J
B) -7.36 *10^-22 J
C) 7.36 *10^-19 J
D) 1.74 *10^-18 J
E) -7.36 *10^-25 J

Question 14

Which of the following requires the smallest energy to separate the ions?

A) CaF₂
B) KF
C) NaF
D) MgF₂
E) LiCl

Question 15

Which of the following solvents will involve ion-dipole interactions with Na⁺?

A) benzene (C₆H₆)
B) carbon tetrachloride (CCl₄)
C) chloroform (CHCl₃)
D) cyclohexane (C₆H₁₂)
E) pentane (C₅H₁₂)

Question 16

Which of the following diagrams best shows a set of polar molecules interacting through dipole-dipole interactions?

A)
B)
C)
D)

Question 17

The interaction energy of LiF is -1.14 *10^-18 J. What is the distance between the Li⁺ and F^- ions?

A) 203 nm
B) 203 pm
C) 0.203 pm
D) 494 pm
E) 302 pm

Question 18

Which of the following compounds is capable of dipole-dipole interactions?

A) CH₄
B) CO₂
C) H₂CO
D) SF₆
E) NH₄⁺

Question 19

Dipole-dipole interactions typically are not as strong as ion-dipole interactions because ________

A) ion-dipole interactions involve partial charges caused by the equal sharing of electrons by atoms forming a bond.
B) dipole-dipole interactions involve the complete transfer of charge between atoms.
C) ion-dipole interactions only involve the partial transfer of charge between atoms.
D) ion-dipole interactions always involve water.
E) dipole-dipole interactions only involve partial charges caused by unequal sharing of electrons by atoms forming a bond.

Question 20

Which of the following will have the largest cation-anion attraction?

A) NaF
B) NaCl
C) NaBr
D) NaI
E) CsCl

Question 21

Which molecule does not exhibit hydrogen bonding?

A) HF
B) CH₃NH₂
C) CH₃OH
D) (CH₃)₃N
E) CH₃CH₂OH

Question 22

The solubility of a compound is determined by ________

A) solute-solvent interactions.
B) solute-solute interactions.
C) solvent-solvent interactions.
D) the change in entropy.
E) all of the items listed.

Question 23

Which of the following nonpolar molecules will have the highest boiling point?

A) CO₂
B) C₆H₆ (benzene)
C) C₆F₆ (hexafluorobenzene)
D) C₂H₂
E) CF₄

Question 24

Polarizability refers to ________

A) the ease with which the electron cloud of an atom or molecule can be distorted.
B) the magnitude of the dipole moment of a molecule.
C) the ease with which a hydrogen bond can form.
D) the perturbation in electron density because of hydrogen bonding.
E) the ability to transmit polarized light.

Question 25

Of the two compounds shown below, one is slightly soluble in water and the other is insoluble in water. Identify the slightly soluble compound and explain why it is soluble in water.
I. ClCH₂CH₂Cl
II. CHCl₂CH₃

A) I because it can form hydrogen bonds with water at each end of the molecule.
B) I because it has stronger dispersion interactions with water.
C) II because it has stronger dipole-dipole interactions with water.
D) II because it has stronger dispersion interactions with water.
E) I because it is nonpolar.

Question 26

Molecular nitrogen (N₂) interacts with water and is sparingly soluble in water due to ________

A) dispersion forces.
B) dipole-induced dipole forces.
C) ion-dipole forces.
D) hydrogen bonding.
E) dipole-dipole forces.

Question 27

Which of the following compounds is capable of hydrogen bonding?

A) CH₃OCH₃
B) CH₃COCH₃
C) CH₃CH₂OH
D) H₂CO
E) CH₃F

Question 28

Of all the noble gases, ________ has the weakest intermolecular force and hence the lowest boiling point.

A) He
B) Ne
C) Ar
D) Kr
E) Xe

Question 29

Indicate which of the following molecules exhibits the greatest dispersion forces.

A) CH₃CH₃
B) CH₃CH₂CH₃
C) C₂H₂
D) CH₄
E) CH₃CH₂CH₂CH₃

Question 30

Which of the following representations best shows the formation of an instantaneous dipole moment between two nonpolar molecules?

A)
B)
C)
D)

Question 31

Of all the noble gases, ________ has the strongest intermolecular force and hence the highest boiling point.

A) He
B) Ne
C) Ar
D) Kr
E) Xe

Question 32

Indicate which of the following nonpolar compounds will have the lowest boiling point.

A) CCl₄
B) CI₄
C) CF₄
D) CH₄
E) CBr₄

Question 33

A substance that is ________ will be insoluble in water, but a substance that is ________ will be soluble in water.

A) hydrophobic; immiscible
B) immiscible; hydrophobic
C) hydrophilic; miscible
D) hydrophobic; hydrophilic
E) miscible; immiscible

Question 34

Normal boiling points of branched alkane hydrocarbons generally are lower than for straight-chain hydrocarbons of the same molar mass because the straight-chain hydrocarbons ________

A) have stronger dipole-dipole interactions.
B) have many more electrons.
C) have more C-H bonds.
D) have a larger surface area and come in closer contact with each other.
E) react with each other to form long chains.

Question 35

Arrange the following compounds in order of increasing dispersion interactions: CCl₄, CH₄, C₃H₈.

A) CH₄ < C₃H₈ < CCl₄
B) CCl₄ < CH₄ < C₃H₈
C) C₃H₈ < CH₄ < CCl₄
D) CCl₄ < C₃H₈ < CH₄
E) CH₄ < CCl₄ < C₃H₈

Question 36

Which of the following compounds would you most appropriately call hydrophobic?

A) CH₄
B) H₂CO
C) CO
D) HCl
E) NaCl

Question 37

Which statement about a hydrogen bond is not correct?

A) Hydrogen bonds involve hydrogen bonded to carbon, nitrogen, oxygen, or fluorine.
B) In a hydrogen bond, the hydrogen atom on one molecule is attracted to unpaired electrons associated with nitrogen, oxygen, or fluorine on another molecule.
C) A hydrogen bond can be thought of as a very strong dipole-dipole interaction.
D) The presence of hydrogen bonds leads to anomalously high boiling points for liquids.
E) Hydrogen bonds stabilize the double helix structure of DNA.

Question 38

When two liquids mix completely in all proportions, they are ________

A) soluble.
B) miscible.
C) insoluble.
D) solvated.
E) ubiquitous.

Question 39

Hydrophilic substances ________

A) are immiscible in water.
B) are insoluble in water.
C) are soluble in water.
D) are hydrated.
E) generally do not hydrogen bond.

Question 40

Dispersion forces are due to ________

A) permanent dipoles.
B) temporary dipoles.
C) hydrogen bonding.
D) ionic interactions.
E) protons.

Question 41

The smell of fresh-cut pine is due in part to a cyclic alkene called pinene. A graph of the natural logarithm of the vapor pressure of pinene vs. 1/temperature produces a straight line with a slope of -4936.37 K. What is the enthalpy of vaporization of pinene?

A) +397 kJ/mol
B) -39.7 kJ/mol
C) +39.7 kJ/mol
D) -41.0 kJ/mol
E) +41.0 kJ/mol

Question 42

Which statement about vapor pressure of a pure liquid is not correct?

A) The vapor pressure is the pressure of the gas at a given temperature in equilibrium with its liquid phase.
B) The temperature at which the vapor pressure equals 760 torr is called the normal boiling point of the substance.
C) The vapor pressure increases with increasing temperature.
D) The vapor pressure increases with increasing surface area of the liquid.
E) Substances with weak intermolecular forces have high vapor pressures at a given temperature.

Question 43

Which alkane compound has the highest vapor pressure?

A) C₄H₁₀
B) C₅H₁₂
C) C₆H₁₄
D) C₇H₁₆
E) C₈H₁₈

Question 44

The vapor pressure of a liquid increases with increasing temperature because ________

A) more molecules can escape from the liquid because their average kinetic energy is greater.
B) the number of gas molecules above the liquid does not change but their average kinetic energy increases.
C) the molecules in the liquid move faster and exert a greater pressure.
D) the ideal gas law states that the pressure is proportional to the temperature.
E) molecules interact less strongly at higher temperatures.

Question 45

Which of the following statements correctly characterizes the rate of evaporation of a liquid?
I. Increases with increasing temperature because molecules have higher kinetic energies.
II. Increases with increasing surface area of the liquid because more molecules are located at the surface.
III. Decreases with stronger intermolecular forces because molecules are less able to escape from the surface of the liquid.

A) I only
B) II only
C) III only
D) I and II only
E) All three: I, II, and III

Question 46

A phase diagram shows the states of a substance as a function of ________ and ________.

A) pressure; volume
B) volume; temperature
C) pressure; temperature
D) concentration; temperature
E) density; pressure

Question 47

Indicate which of the following pairs of compounds is most likely to be miscible.

A) H₂O and CH₃CH₂CH₂CH₃
B) Br₂ and HI
C) HF and CCl₄
D) CCl₄ and Br₂
E) CCl₄ and NH₃

Question 48

Which of the following compounds would be most soluble in carbon tetrachloride, CCl₄?

A) H₂O
B) CH₃OH
C) NH₃
D) C₆H₆
E) HCl

Question 49

Which alkane compound has the highest boiling point?

A) C₄H₁₀
B) C₅H₁₂
C) C₆H₁₄
D) C₇H₁₆
E) C₈H₁₈

Question 50

Which alcohol should be most soluble in a nonpolar solvent such as hexane, C₆H₁₄?

A) CH₃OH
B) CH₃CH₂OH
C) CH₃CH₂CH₂OH
D) CH₃CH₂CH₂CH₂OH
E) CH₃CH₂CH₂CH₂CH₂OH

Question 51

The aroma from almonds and cherries is due in part to a compound called benzaldehyde. A graph of the natural logarithm of the vapor pressure of benzaldehyde vs. 1/temperature produces a straight line with a slope of -5870.99 K. What is the enthalpy of vaporization of benzaldehyde?

A) +473 kJ/mol
B) -47.3 kJ/mol
C) +47.3 kJ/mol
D) -48.8 kJ/mol
E) +48.8 kJ/mol

Question 52

Which of the following compounds do you expect to be most soluble in water?

A) CO₂
B) CCl₄
C) O₂
D) SiO₂
E) NH₃

Question 53

Which one of the following substances would you predict to have the highest vapor pressure at a given temperature? In these line drawings, a carbon is implicit at the end of a line (bond) or where two or more lines come together. Carbon requires four bonds, so any missing bonds are implicitly bonds to hydrogen atoms.

A)
B)
C)
D)
E)

Question 54

The vapor pressure of a liquid will increase if ________

A) the temperature is increased.
B) the volume available to the gas phase is increased.
C) the volume of the liquid phase is increased.
D) the liquid is stirred.
E) the liquid is put in a container with a larger surface area.

Question 55

Which of the following pairs of compounds is most likely to be immiscible?

A) Br₂ and C₆H₆
B) H₂O and CH₃CH₂OH
C) CCl₄ and H₂CO
D) CH₃OH and CH₃CH₂OH
E) H₂O and NH₃

Question 56

Gasoline is primarily a mixture of hydrocarbons and is sold with an octane rating that is based on a comparison with the properties of isooctane (C₈H₁₈), which has an enthalpy of vaporization of 35.8 kJ/mol and a boiling point of 98.2°C. Determine the vapor pressure of isooctane on a very hot summer day when the temperature is 38°C.

A) 80.0 torr
B) 36.7 torr
C) 67.8 torr
D) 47.9 torr
E) 89.3 torr

Question 57

Portable lanterns and stoves used for camping often use a mixture of hydrocarbons for fuel. One such hydrocarbon is an alkane called n-pentane. These lanterns and stoves are often difficult to light on a cold day because the fuel has a low vapor pressure at low temperatures. Determine the vapor pressure of n-pentane on a night when the temperature is 0.0°C. The enthalpy of vaporization of n-pentane is 27.6 kJ/mol, and its boiling point is 36.0°C.

A) 228 torr
B) 367 torr
C) 184 torr
D) 479 torr
E) 209 torr

Question 58

Which of the following statements does not correctly identify a factor that affects the boiling point of a pure substance?
I. vapor pressure of the liquid
II. strength of intermolecular forces
III. enthalpy of vaporization
IV. surface area of the liquid

A) I only
B) II only
C) III only
D) IV only
E) III and IV only

Question 59

Gasoline is primarily a mixture of hydrocarbons and is sold with an octane rating that is based on a comparison with the combustion properties of isooctane. Gasoline usually contains an isomer of isooctane called tetramethylbutane (C₈H₁₈), which has an enthalpy of vaporization of 43.3 kJ/mol and a boiling point of 106.5°C. Determine the vapor pressure of tetramethylbutane on a very hot summer day when the temperature is 38°C.

A) 80.0 torr
B) 36.7 torr
C) 67.8 torr
D) 47.9 torr
E) 89.3 torr

Question 60

Which of the following statements does not correctly characterize the rate of evaporation of a liquid?
I. Increases with increasing temperature because molecules have higher kinetic energies.
II. Increases with increasing surface area of the liquid because more molecules are located at the surface.
III. Increases with stronger intermolecular forces because molecules in the liquid repel each other more.

A) I only
B) II only
C) III only
D) I and II only
E) II and III only

Question 61

The temperature at point a in the phase diagram below is the ________

A) critical point.
B) triple point.
C) transition point.
D) normal freezing point.
E) normal boiling point.

Question 62

At the triple point of a substance, ________

A) three phases are present in equilibrium.
B) the solid sublimes.
C) the gas condenses to a liquid.
D) solid and liquid are in equilibrium.
E) only one phase appears to be present.

Question 63

At the point marked with a dot on the phase diagram, the solid will ________

A) be indistinguishable from the gas.
B) boil.
C) melt.
D) sublime.
E) liquefy.

Question 64

Consider the phase diagram for a substance shown here. The line between the solid and liquid phases has a positive slope because the solid phase is ________ than the liquid phase.

A) more dense
B) less dense
C) more massive
D) less massive
E) hotter

Question 65

On the phase diagram below, identify the normal melting point.

A) VI
B) V
C) VII
D) IV
E) III

Question 66

The temperature at point b in the phase diagram below is the ________

A) critical point.
B) triple point.
C) transition point.
D) normal freezing point.
E) normal boiling point.

Question 67

Which of the following substances has a solid that is less dense than the liquid?

A)
B)
C)
D)

Question 68

Point c in the phase diagram below is the ________

A) critical point.
B) triple point.
C) transition point.
D) normal freezing point.
E) normal boiling point.

Question 69

On the phase diagram below, identify the normal boiling point.

A) VI
B) V
C) VII
D) IV
E) III

Question 70

Consider the phase diagram for a substance such as the one shown here. If the line between the solid and liquid phases has a negative slope, then the solid phase is ________ than the liquid phase.

A) more dense
B) less dense
C) more massive
D) less massive
E) hotter

Question 71

Which statement about the phase diagram below is not correct?

A) The critical point is not shown.
B) D is the normal boiling point.
C) The vapor pressure of the solid is zero below the triple point.
D) The normal melting point is at a lower temperature than the triple point.
E) E, F, and G label in that order the solid, liquid, and gas phases.

Question 72

Condensation occurs in going from region ________

A) I to II.
B) I to III.
C) II to III.
D) III to II.
E) III to I.

Question 73

Which of the following substances is a solid at 25°C and 1 atm?

A)
B)
C)
D)

Question 74

Which of the following substances has a solid whose freezing point will decrease with increasing pressure?

A)
B)
C)
D)

Question 75

Sublimation occurs in going from region ________

A) I to II.
B) I to III.
C) II to III.
D) III to II.
E) III to I.

Question 76

Melting occurs in going from region ________

A) I to II.
B) I to III.
C) II to III.
D) III to II.
E) III to I.

Question 77

What does the line indicated by the arrow in the following phase diagram represent?

A) solid-liquid boundary
B) solid-gas boundary
C) liquid-gas boundary
D) triple point
E) solid-solid boundary

Question 78

At the critical point, ________

A) all the liquid has evaporated.
B) the densities of the solid and the liquid are the same.
C) the densities of the solid and the gas are the same.
D) the densities of the gas and the liquid are the same.
E) a critical mass has been reached.

Question 79

Point d in the phase diagram below is the ________

A) critical point.
B) triple point.
C) transition point.
D) normal freezing point.
E) normal boiling point.

Question 80

The phase diagram for carbon dioxide is shown below. What is the phase that exists at room temperature and pressure (22^oC, 1 atm)?

A) gas
B) liquid
C) solid I
D) supercritical fluid
E) solid II