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