Chapter 11

A mixture containing 21.4 g of ice (at exactly 0.00 °C) and 75.3 g of water (at 55.3 °C) is placed in an insulated container. Assuming no heat is lost to the surroundings, what is the final temperature of the mixture? 32.6 °C 43.0 °C 25.4 °C 45.6 °C

25.4 °C

The vapor pressure of a substance is measured over a range of temperatures. A plot of the natural log of the vapor pressure versus the inverse of the temperature (in Kelvin) produces a straight line with a slope of -3.46 × 103 K. What is the enthalpy of vaporization of the substance? 0.416 kJ/mol 28.8 kJ/mol 2.40 × 10^-3 kJ/mol 283 kJ/mol

28.8 kJ/mol

Determine the amount of heat (in kJ) required to vaporize 1.55 kg of water at its boiling point. For water, ΔHvap = 40.7 kJ/mol (at 100 °C.) 3.50 × 10^3 kJ 63.1 kJ 2.11 kJ 1.14 × 10^6 kJ

3.50 × 103 kJ

water surface tension

72.8 mJ/m2

Acetic acid has a normal boiling point of 118 °C and a ΔHvap of 23.4 kJ/mol. What is the vapor pressure (in mmHg) of acetic acid at 25 °C? 80.5 mmHg 758 mmHg 7.17 × 10^3 mmHg 2.92 × 10^-39 mmHg

80.5 mmHg

Sublimation

A change directly from the solid to the gaseous state without becoming liquid

Viscosity

A liquid's resistance to flowing

phase diagram

A map of the state (or phase) of a substance as a function of pressure and temperature.

permeant dipole

A permanent separation of charge; a molecule with a permanent dipole always has a slightly negative charge at one end and a slightly positive charge at the other.

Hydrogen bonding

A strong dipole-dipople attractive force between a hydrogen bonded to O, N, or F and one of these electronegative atoms on a neighboring molecule.

ion-dipole force

An intermolecular force between an ion and the oppositely charged end of a polar molecule.

dispersion

An intermolecular force exhibited by all atoms and molecules that results from fluctuations in the electron distribution

dipole-dipole forces

An intermolecular force exhibited by polar molecules that results from the uneven charge distribution

One of these substances is a liquid at room temperature. Which one? CO2 CH3OH CF4 SiH4

CH3OH Methanol (CH3OH) contains hydrogen directly bonded to oxygen, so it has hydrogen bonding. Hydrogen bonding is a strong intermolecular force that makes this substance a liquid at room temperature.

crystalline

Describes a solid in which atoms, molecules, or ions are arranged in patterns with long-range, repeating order.

Boiling point of noble gases

Helium, Neon, Argon, Xenon, Kr

Taking intermolecular forces into account, which halogen would you expect to have the highest boiling point? F2 I2 Cl2 Br2

I2 Since boiling point increases with increasing strength of intermolecular forces, and since the halogens only have the dispersion force (which increases with increasing molar mass), the boiling points of the halogens increase with increasing molar mass. Iodine has the highest molar mass of the halogens in this list, so it has the highest boiling point.

Which substance experiences dipole-dipole forces? CS2 SO3 CCl4 NF3

NF3 The N—F bond is polar and its geometry is trigonal pyramidal. Therefore, the three polar bonds sum to an overall dipole moment and NF3 experiences dipole-dipole forces.

nonvolatile

Not easily vaporized

volatile

Tending to vaporize easily

Clausius-Clapeyron equation (two-point form)

The Clausius-Clapeyron equation can also be expressed in a two-point form that we can use with just two measurements of vapor pressure and temperature to determine the heat of vaporization

capillary action

The ability of a liquid to flow against gravity up a narrow tube due to adhesive and cohesive forces.

miscibility

The ability of substances to mix without separating into two phases.

heat of fusion ( delta H fus)

The amount of heat required to melt 1 mole of a solid

Condensation

The change of state from a gas to a liquid

Vaporization

The change of state from a liquid to a gas

Clausius-Clapeyron equation

The equation the displays the exponential relationship between vapor pressure and temperature

critical point

The temperature and pressure above which a supercritical fluid exists

boiling point

The temperature at which the vapor pressure of a liquid equals the external pressure

triple point

The unique set of conditions at which all three phase of a substance are equally stable and in equilibrium

amorhous

describes a solid in which atoms or molecules do not have any long-range order

heating curve for water

diagram

Determine which state this substance is in at 1 atm and 298 K by referring to its phase diagram. gas liquid solid all three states in equilibrium

gas

What state of matter is compressible? gas liquid solid

gas Gases are compressible because the atoms or molecules in a gas have a great deal of space between them.

Properties of matter

gas, liquid, solid

A sample of the substance in this phase diagram is initially at 175 °C and 925 mmHg. Which phase transition occurs when the pressure is decreased to 760 mmHg at constant temperature? liquid to solid solid to liquid liquid to gas solid to gas

liquid to a gas At 175°C and 925 mmHg, this substance is a liquid. When the pressure is decreased, the vaporization curve is crossed and the substance becomes a gas.

Stages of Water

steam, water, ice

heat of vaporization

the amount of heat required to vaporize one mole of a liquid to a gas

intermolecular forces

the attractive forces that exist among the particles that compose matter. dispersion, dipole-dipole, hydrogen bonding and ion-dipole bonding

Which process releases the greatest amount of heat? the freezing of 10 g of liquid water the boiling of 10 g of liquid water the condensation of 10 g of gaseous water the melting of 10 g of ice

the condensation of 10 g of gaseous water The enthalpy of condensation is negative (so condensation releases heat) and its absolute value is greater than the enthalpy of fusion.

vapor pressure

the partial pressure of a vapor that is in dynamic equilibrium with its liquid

dynamic equilibrium

the point at which the rate of the reverse reaction or process equals the rate of the froward reaction or process

critical pressure (Pc)

the pressure required to bring about a transition to a liquid at the critical temperature

critical temperature (Tc)

the temperature above which a liquid cannot exist, regardless of pressure

melting point

the temperature at which the molecules of a solid have enough thermal energy to overcome intermolecular forces and become a liquid

normal boiling point

the temperature at which the vapor pressure of a liquid equals 1 atm

surface tension

the tendency of liquids to minimize their surface area. The energy required to increase the surface area of a liquid by a unit amount' responsible for the tendency of liquids to minimize their surface area, giving rise to a membrane-like surface.

Deposition

the transition from gas to solid

Which property of a liquid increases with increasing temperature? surface tension viscosity vapor pressure none of the above

vapor pressure Vapor pressure increases with increasing temperature, since more of the particles have sufficient energy to leave the liquid phase as temperature increases.

Heats of vaporization of different liquids

water, rubbing alcohol, acetone, diethyl ether