Chemistry 2 - LS Prelecture 1

Which of the following options correctly describe a phase equilibrium? Select all that apply.

-At equilibrium, the amount of the substance in each phase remains constant. -If the rate of condensation is equal to the rate of evaporation, a phase equilibrium exists. -A system must be closed in order for a phase equilibrium to be established.

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

-At the melting point of a substance the solid and liquid phases are in equilibrium -Pressure changes have little effect on the melting point of a substance.

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. -For two compounds of similar molar mass, the greater the molecular dipole moment, the stronger the dipole-dipole forces.

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 O-H bonds -One or more N-H bonds

Which of the following options correctly describe the boiling point of a substance? Select all that apply.

-The boiling point of a substance increases as the external pressure increases. -The boiling point is the temperature at which the vapor pressure equals the external pressure. -Boiling occurs when the vapor pressure of the liquid is sufficient for bubbles of vapor to form in the interior of the liquid.

Which of the following statements correctly interpret the phase diagram shown? Select all that apply.

-The normal boiling point of this substance is 135oC. -The arrow marked 1 represents a change from the solid to the liquid phase.

Which of the following statements correctly describe bonding and intermolecular forces? Select all that apply.

-bonding forces are generally much stronger than intermolecular forces -intermolecular forces involve partial or small charges that are far apart and are relatively weak -for a molecular substance, the strength of the intermolecular forces determines the physical properties of its phases

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

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

Match each marked point and arrow in the phase diagram shown with the correct description.

1 = Triple point 2 = A liquid cools down, freezes, and cools further. 3 = A gas is compressed at constant temperature and becomes a liquid. 4 = Critical point 5 = A substance in the solid phase

Which of the following correctly defines a phase of matter?

A physical state that is physically distinct and homogeneous

Which of the following correctly describes a heating-cooling curve?

A plot of heat vs. temperature for a substance that is heated or cooled at a constant rate and constant pressure

Match each statement about forces of attraction to the correct description.

Covalent bonds are classified as = intramolecular forces. Intermolecular forces = are the forces of attraction between one individual molecule and another. The physical state of a molecular substance at a particular temperature and pressure depends on the strength of its = intermolecular forces. A change in the physical state of a molecular substance does NOT involve the breaking of = covalent bonds.

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

False

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

False

______ involve the attraction between an charged particle and a nearby polar molecule. The most common example of such an intermolecular force of attraction is the dissolution of an ionic compound by water.

Ion-dipole forces

Dispersion forces are the only type of intermolecular force exhibited by atoms and by ___ molecules. Without the existence of dispersion forces, such substances could not exist in the ___ states of matter.

Nonpolar; condensed.

A physical state of matter that is chemically and physically uniform is called a(n) _____.

Phase

In which of the following stages are both the liquid and the gas phases of the substance present?

Stage 2

Which of the following options correctly defines polarizability?

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

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

True

Match each term with its correct definition.

covalent radius = Half the distance between the nuclei of two covalently bonded atoms van der Waals radius = Half the shortest distance between the nuclei of two identical nonbonded atoms bond length = The distance between the nuclei of two bonded atoms van der Waals distance = The shortest distance between two non-bonded atoms in adjacent molecules

Half the distance between the nuclei of two covalently bonded atoms is the ______, whereas half the shortest distance between the nuclei of identical nonbonded atoms is the ______.

covalent radius; van der Waals radius

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

If a liquid is placed in a closed container, molecules with sufficient ___ 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 ___.

energy, rates, equilibrium

The boiling point of a substance is the temperature at which the vapor pressure of the substance is _____ the external pressure; hence the boiling point depends on the applied pressure.

equal to

The phase changes of many substances are reversible, and a phase change, just like a chemical reaction, may reach ___ providing it takes place in a(n) ___ system.

equilibrium, closed

Condensation, freezing, and deposition are _____ phase changes, whereas melting, vaporization, and sublimation are _____ changes.

exothermic; endothermic

Match each phase change correctly to the term used to describe the process.

gas to liquid = condensation liquid to solid = freezing solid to gas = sublimation liquid to gas = vaporization solid to liquid = melting gas to solid =deposition

A heating-cooling curve shows the changes that occur when ___ is added to or removed from a sample of matter at a ___ rate.

heat, constant

In a molecular substance, the covalent bonds between the atoms hold the individual molecule together as a unit and are referred to as _____ forces. The nonbonding forces of attraction between one individual molecule and another are called _____ forces. The physical behavior of the phases of matter reflect the difference in the strength of their _____.

intramolecular; intermolecular; intermolecular forces

As the temperature of a substance increases, the average ___ energy of its particles also increases, and movement overcomes forces of ___ more easily. As temperature decreases, particles move more slowly, and the ___ forces between particles dominate.

kinetic attraction attraction

The melting point of a substance is the temperature at which the particles have enough ___ energy to break free from the ___ phase and enter the ___ phase.

kinetic, solid, liquid

At _____ temperatures the forces of attraction between particles dominate because the particles are moving slowly. At _____ temperatures the movement of the particles overcomes the attractions.

lower; higher

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

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 hydrogen

Match each lettered portion of the following heating curve to the correct description.

p = The substance is in the solid phase. s = The substance is changing from liquid to vapor. q = Both solid and liquid phases are present. r = the kinetic energy of the liquid particles is increasing. t = The particles are far apart and movement dominates the phase.

The term _____ is used to describe how well the electron cloud around an atom responds to changes in its electronic environment.

polarizability