Chapter 11

Which of the marked interactions are hydrogen bonds? Select all that apply.

1 3 Reason: Bond 2 and 4 are covalent bonds between N and H.

The H2O molecule has ________ covalent O-H bonds and ________lone pairs on the oxygen atom. This means that each H2O molecule can form a maximum of_________ H bonds with neighboring H2O molecules. The hydrogen bonding in H2O is therefore very effective.

2 2 4- one for each H and one for each lone pair on the O

Which of the following compounds exhibit hydrogen bonding between their molecules? Select all that apply.

A B E Reason: Compound C and D contains no O-H, N-H, or H-F bonds and therefore no hydrogen bonding is possible between its molecules.

Which of the following correctly defines a phase of matter?

A physical state that is physically distinct and homogeneous

What is an induced dipole?

An atom or molecule that has a temporary separation of partial charges due to the proximity of an ion or other polar or nonpolar molecule

Which of the following are intermolecular forces? Select all that apply.

Dipole-dipole forces Hydrogen bonding Dispersion forces

Which of the following statements correctly describe dipole-dipole forces? Select all that apply.

Dipole-dipole forces are the forces of attraction between two polar molecules. The larger the dipole moment the greater the dipole-dipole force between two molecules. The molecule must have an overall dipole moment to exhibit dipole-dipole forces. A molecule may contain polar bonds but be nonpolar overall. Dipole-dipole forces arise from the attraction between oppositely charged poles on adjacent molecules.

Which of the following are intermolecular forces? Select all that apply.

Dipole-induced dipole forces Ion-dipole forces

Which intermolecular forces exist between molecules of a nonpolar substance?

Dispersion forces

True or false: A bond between O and H within any molecule is called a hydrogen bond.

False Reason: A hydrogen bond is an intermolecular attraction between a hydrogen atom and a lone pair of electrons on an O, N, or F atom in another molecule or a different part of the same molecule. A hydrogen bond cannot exist between two atoms that are already covalently bonded to each other. To participate in hydrogen bonding, a hydrogen atom must be covalently bonded to N, O, or F.

True or false: Dispersion forces are exhibited only by nonpolar molecules.

False Reason: Dispersion forces are experienced by ALL particles (atoms, ions, and molecules). Dispersion forces are, however, the only intermolecular force experienced by nonpolar molecules and atoms.

Which substances can exhibit dipole-dipole intermolecular forces? Select all that apply.

H2S CO SO2

Within a phase

Heat change causes a temperature change.

During a phase change

Heat is added or removed but temperature remains the same.

In which state(s) of matter are the particles held closely together? Select all that apply.

Liquid Solid

A fixed amount of a molecular substance in the liquid phase is placed in a flask at constant temperature. The flask is closed and is allowed to come to equilibrium. Select all the statements that correctly describe the processes occurring in the flask.

Molecules are leaving and entering the liquid phase at the same rate. The relative amounts of liquid and vapor in the flask remain constant.

When hydrogen is covalently bonded to ________ , oxygen, or fluorine there will be an attraction between such a hydrogen and a(n) ______________ pair of electrons on a nitrogen, oxygen, or fluorine atom on an adjacent molecule. This attraction is called a(n) _________ bond and it is the strongest type of intermolecular force between neutral species.

Nitrogen Lone / nonbonding, single, unshared, free Hydrogen Bond

Which of the following structural features would allow a molecular substance to exhibit hydrogen bonding between its molecules? Select all that apply.

One or more N-H bonds One or more O-H bonds Reason: Not all hydrogen atoms can form hydrogen bonds. Only hydrogen atoms covalently bonded to N, O, or F can form hydrogen bonds. Reason: The presence of an oxygen atom alone does not allow a molecule to form hydrogen bonds between its molecules. In addition to an oxygen atom, the molecule must also contain a hydrogen atom capable of hydrogen bonding (i.e., a hydrogen atom covalently bonded to N, O, or F).

Which of the following options correctly defines polarizability?

Polarizability is a measure of how the electron cloud around an atom responds to its electronic environment.

Which of the following statements correctly describe melting and melting point? Select all that apply.

Pressure changes have little effect on the melting point of a substance. At the melting point of a substance the solid and liquid phases are in equilibrium. Reasons for wrong answers: Reason: Since the particles of liquids and solids are close together, melting point is only slightly affected by pressure changes. Reason: During melting there is no change in temperature, therefore no change in the average kinetic energy of the particles. It is the potential energy that increases during the melting process.

Which of the following statements correctly describe the surface tension of a liquid? Select all that apply. (Assume the liquid is a molecular substance.)

Surface tension is the result of a net downward and inward force on the surface particles of a liquid. Surface tension is the amount of energy required to increase the surface area of a liquid by a unit area. A polar liquid will have a higher surface tension than a nonpolar liquid.

As the boiling point graph shows, H2O, NH3, and HF deviate from the boiling point trend shown for the hydrides of the carbon group. Select the statement that correctly explains this deviation.

The H bonding between molecules of H2O, NH3, and HF is much stronger than the intermolecular forces between CH4 molecules.

What will occur when a liquid is placed into a closed, evacuated container?

The liquid will evaporate until equilibrium with its vapor is reached.

Which of the following statements correctly describe vapor pressure? Select all that apply.

The vapor pressure of a molecular substance depends on the strength of its intermolecular forces. The vapor pressure is the pressure exerted by the vapor above a liquid at equilibrium. Vapor pressure increases as temperature increases.

H2O, NH3, and HF deviate from the boiling point trend shown for the hydrides of the carbon group

They have a higher boiling point

True or false: A compound containing one or more oxygen atoms is not necessarily capable of forming hydrogen bonds between its molecules.

True Reason: The presence of oxygen alone is not sufficient to allow a compound to form hydrogen bonds between its molecules. In addition to oxygen, the compound must have a hydrogen atom capable of hydrogen bonding (i.e., a hydrogen atom covalently bonded to N, O, or F).

Which of the following statements correctly describe the viscosity of a liquid? Select all that apply.

Viscosity is a liquid's resistance to flow. The viscosity of a given liquid decreases with increasing temperature. A liquid with stronger intermolecular forces will have a higher viscosity.

A phase change caused by the ______ of heat will result in a(n) ______ of the order of the substance. Select all that apply.

addition; decrease removal; increase Why it isn't the inverse: Reason: Adding heat to a system increases the kinetic energy of its particles and leads to a decrease in order. Reason: Removing heat from a system decreases the kinetic energy of its particles and leads to an increase in order.

Intramolecular forces act ______, while intermolecular forces act ______.

between atoms in a molecule; between molecules in a sample

Within a phase, a change in heat causes the temperature of the substance to _____ as the _____ energy of the molecules changes. During a phase change, however, a change in heat causes a change in the _____ energy of the molecules and the temperature will _____.

change; kinetic; potential; stay the same Explain: Reason: Within a phase, a change in heat causes a change in the kinetic energy of the particles and the temperature therefore changes. By contrast, a change of heat during a phase change causes a change in potential energy, with no accompanying change in temperature.

A liquid rises against the pull of gravity through a narrow space through capillary action. This results from a competition between the _____ intermolecular forces between the molecules of the liquid itself and the _____ forces between the liquid and the walls of the container.

cohesive; adhesive

Bonding forces include ionic bonds, metallic bonds, and _________bonds. These types of forces are much____________than the forces of attraction between individual molecules, which are called _________ forces.

covalent stronger intermolecular or nonbonding

The attraction between an ion and a nearby polar molecule is called an ion - _________ interaction. This attractive force is important when a(n) ___________ compound dissolves in a polar solvent such as H2O.

dipole ionic

Van der Waals forces, or intermolecular forces, include _______ and ________bonding, and dispersion forces.

dipole - dipole Hydrogen

The tetrahedral pattern of hydrogen bonding in H2O gives ice a very open structure with large ________ between the molecules. Water therefore differs from most liquids because it becomes _________ dense when it freezes.

distance less

The process in which a liquid is transformed into a gas at any given temperature is called _____. (Select all that apply.)

evaporation vaporization Boiling point is a specific point and evaporation does not always occur under equilibrium conditions.

Since H2O is able to exhibit different types of intermolecular forces including hydrogen bonding, this substance has a _____ heat capacity and a _____ heat of vaporization compared to other liquids.

high; high

Refer to the boiling point graph shown. H2O, NH3, and HF have much _______ boiling points than the hydrides formed by other elements in the same group. These compounds experience ____________ bonding between their molecules. Since this type of intermolecular force is very ____________it takes more ____________ to separate the molecules so they can move from the liquid to the gas phase.

higher hydrogen strong energy

The nearby presence of a polar molecule or an ion will cause an atom or a nonpolar molecule to develop a temporary separation of charges. The temporarily polarized particle is called a(n) _________ dipole

induced

During a phase change on a heating curve, heat being applied to the system is being used to overcome ________ forces. Thus the ____________ of the system remains constant during a phase change.

intermolecular temperature

The __________ point of a substance is the temperature at which the solid and liquid phases are in equilibrium.

melting

The distances between the particles in a sample of a gas are ______ the distances between particles in a sample of a liquid.

much greater than

When two polar molecules are close to each other they will orient themselves so that the positive pole of one molecule attracts the ________ pole on the adjacent molecule. These intermolecular forces are called ______________-____________ forces

negative dipole-dipole

Evaporation

occurs when particles of sufficient energy escape from the liquid phase into the gas phase.

A physical state of matter that is chemically and physically homogeneous, and separated from other parts of a system by a well-defined boundary, is called a(n)

phase

The change in physical state of a substance, such as the change from solid to liquid, is called a(n) ___________ change. This type of change usually involves the addition or removal of _____________to/from the substance.

phase heat

The ease with which the electron density in an atom or molecule can be distorted its called its ______.

polarizability

If a liquid is placed in a closed container, molecules with sufficient kinetic energy will move from the liquid to the gas phase. Gas phase molecules will in turn condense. Eventually the ____________ of evaporation and condensation will be equal and the system is said to have reached phase __________

rate equilibrium

Intermolecular forces are

responsible for the macroscopic properties of a substance or mixture.

The process in which a substance passes directly from the solid to the vapor phase is called ___________ . The reverse process is called _____________

sublimation deposition

Intramolecular forces are

the bonds that hold individual atoms in a substance together.

The pressure exerted by the ______________ above a liquid at equilibrium is called the equilibrium ____________ pressure. This pressure ___________ as the temperature of the system increases.

vapor vapor increase

Water has many unusual physical properties, such as a high specific heat, and a boiling point that is much higher than molecules of similar size and mass. This is because ______.

water can form multiple hydrogen bonds

Intermolecular forces are generally ______ than the ______ bonds in a molecule.

weaker; covalent