CHAPTER 10 LIQUIDS and SOLIDS
INTERMOLECULAR FORCES
w Forces between molecules that hold them together ______.
w Higher forces lead to higher ______and ______points.
l Dipole –dipole forces
l London dispersion forces
DIPOLE-DIPOLE FORCES
w Result when a ______of polar covalent molecules attract.
w About ______a covalent bond.
w Includes ______
n Indicated by ______
n ______
(ex. ______) form strong interactions with the H.
n High intermolecular bond energy (______)
LONDON DISPERSION FORCES (LDF)
w Exist in ______substances
Ex.
w Caused by ______which arise due
to a ______.
l This leads to an ______in other atoms and an attraction arises between opposite poles.
l Known as ______
w Atoms and molecules with ______are ______.
DECIDING THE IMF that exists first depends on the
INTRAMOLECULAR FORCE inside the molecules.
SAMPLE PROBLEMS
1. The boiling point of Argon is –189.4°C
n Why is it so low?
n How does it prove that London forces exist?
n Why is Xenon’s bp higher (-111.9 °C)?
2. Put the following in order from lowest to highest bp.
C2H6, NH3, F2
LIQUID PROPERTIES
w Low ______
w Lack of______
w More dense than ______
SURFACE TENSION
w Forms spherical droplets because of ______– minimizes surface area
w Higher molecular force à ______
CAPILLARY ACTION
w ______of a liquid up a tube.
w Why would mercury form a convex meniscus and water a concave miniscus?
n ______– intermolecular force between the molecules of the liquid.
n ______– force between the liquid and the container
l Glass has ______
So, which liquid is more attracted to the glass? What does this do to the shape of the meniscus?
VISCOSITY
w A measure of the liquid’s ______.
w Higher intermolecular forces
= ______
w ______because the molecules get “tangled” in one another.
VAPOR PRESSURE
w Liquid in a closed container ______
and ______continuously until an
______is reached.
(______)
w known as the ______of the liquid.
w Vapor pressure ______
because molecules have more ______can
escape into the gas phase easily.
HIGH VAPOR PRESSURE
w ______– evaporate easily from an open container.
w ______intermolecular forces
w More molecules ______
LOW VAPOR PRESSURE
w ______
w Large number of ______holding
the molecules together in the liquid phase.
w Higher ______(more London
dispersion forces)
RELATING VAPOR PRESSURE TO TEMPERATURE
w ______equation
n Relates temperature, Enthalpy of vaporization, and the vapor pressure at different temperatures.
w Uses the gas constant ______or
______.
SAMPLE PROBLEMS
w The vapor pressure of 1-propanol at 14.7C is 10.0 torr. The heat of vaporization if 47.2 kj/mol. Calculate the vapor pressure at 52.8C.
w Which has greater surface tension N2 or Br2?
PHASE DIAGRAMS
w Represent the phases of a substance as a function of ______and ______.
w Any ______can be represented using a phase diagram.
w Sometimes ______are also represented.
POINTS of INTEREST ON A PHASE DIAGRAM
w Normal melting point – the temperature at which the ______phase when the atmospheric pressure = ______.
w Normal boiling point – the temperature at which the ______phase when the atmospheric pressure = ______.
w Triple point – the temperature and pressure at which
______coexist
w Critical point – the temperature beyond which the ______cannot exist.
PHASE CHANGES
Melting
Freezing
Sublimation
Deposition
Vaporization
Condensation
H2O PHASE DIAGRAM
CO2 PHASE DIAGRAM
PHASE CHANGE CALCULATIONS
What is the heat in Joules required to convert 25 grams of -10 °C ice into 150 °C steam?
Useful information:
heat of fusion of water = 334 J/g
heat of vaporization of water = 2257 J/g
specific heat of ice = 2.09 J/g·°C
specific heat of water = 4.18 J/g·°C
specific heat of steam = 2.09 J/g·°C
SOLIDS
1.
2.
3.
4.
PROPERTIES OF IONIC SOLIDS
1. Low ______and high ______
· Due to strong ______between positive and negative ions in the 3D array
o Attraction amount varies according to Coulomb’s law
§ ______yield higher Coulombic attraction
§ ______on ions yield higher Coulombic attraction
2. Brittle
· Due to ______of like charged ions when the layers slide past each other.
3. Non – conductors in the ______
· Due to charged ions being locked in position
· However, once ______or
______in solution, the ions are free to move and will be able to pass a current.
4. Soluble in ______/ insoluble in
______solvents.
· Due to ______interactions between water and ionic compounds.
· Attractions ______ionic compound outweigh the interactions with non-polar solvents.
PROPERTIES of METALLIC SOLIDS
1. Good ______
· Electrons are free to move around the positive kernels in the electron sea model.
2. Malleable and ductile
· Deforming the solid does not change the environment immediately surrounding each positive metal core.
3. Can be alloyed
w Electron sea remains so alloys will still ______.
w ______– smaller atoms fill interstitial spaces between the large atoms.
o Ex. Steel ______
o ______usually increases
o Rigidity increases
§ malleability and ductility reduces
w ______– atoms of similar radius where one is substituted for another
o Ex. Brass ______
o Density will be a ______of the metals
o Still remains malleable and ductile
PROPERTIES of COVALENT NETWORK SOLIDS
Formed by covalently bonded nonmetals (especially the C family)
w Elements ex. ______
w Compounds ex. ______
1. High melting points
w Since all atoms are covalently bonded
2. Rigid and hard
· 3D arrangement of covalent bond angles that are fixed
EXAMPLES:
SPECIFIC COVALENT NETWORK SOLIDS
o GRAPHITE
o Graphite is soft due to ______hybridization.
Sheets of 2 D networks that can ______past
each other. Sheets are held together primarily by
______
· SILICON
o 3 D network similar to diamond
o Semiconductor since it is a metalloid
w Conductivity increases with temperature
w N-type doping – ______carrying due to adding an element with an extra valence electron (ex. P)
w P- type doping - ______carrying due to adding an element with one less valence electron (ex. Ge)
PROPERTIES of MOLECULAR SOLIDS
Consist of nonmetals (including noble gases), diatomic elements, or compounds (sometimes large polymers) formed from 2 or more non-metals held together by intermolecular forces only.
1. Non-conductors
w Because electrons are bound within the ______of each molecule within the solid.
2. Low ______
w due to only ______existing between the particles
IONIC / METALLIC / COVALENT NETWORK / MOLECULARConduct in solid state / Yes / Si semiconductor
Conduct when melted / Yes / Yes / Si semiconductor
Conduct when in aq solution / Yes
Melting point / High / Wide range / Extremely high / Low
Rigid / Brittle / Malleable/ ductile / Hard
Exception: graphite
Other distinct features / Can be alloyed / Thermal insulators
C family / Non-metals – compounds, diatoms, noble gases, polymers
CHAPTER 11 PROPERTIES OF SOLUTIONS
(11.1-11.3) Concentration of solutions
Enthalpy of solution (D H soln)
Factors affecting solubility
· Structure – likes dissolves likes
· Pressure – gases (Henry’s law)
(11.4) Temperature
(11.5) Vapor pressure of solutions
Raoult’s law
· Ideal vs. non-ideal solutions
Colligative properties
(11.5 + 11.7) Boiling point elevation and freezing point depression in non-electrolytes and electrolyte solutions
· Vant Hoff factor
(11.6) Osmotic pressure
COMPOSITION of SOLUTIONS
______– the substance that is being dissolved
______– the substance doing the dissolving
If both are liquids, the one that is present in higher proportions is the solvent.
MOLARITY
M =
Ex. Calculate the molarity of a solution of glucose, if 250.0 g are dissolved in 350.0 ml of solution.
MASS %
% by mass =
Ex. A solution of vinegar is 5.0% by mass acetic acid. Calculate the mass of acetic acid dissolved in 5.0 L water if the solution has a density of1.08 g/ml.
MOLE FRACTION
Recall from the gas laws chapter.
Compares the number of moles of one part of the solution to the total number of moles in the solution.
X =
Practice problem:
1. A solution was made by adding 5.84 g of H2CO to 100.0 g of water. The final volume of solution was 104.0 ml.
2. Calculate Molarity
3. Molality
4. % by mass
5. Mole fraction
ENERGY OF SOLUTION
3 steps to solution formation:
1. Break the solid into individual components
Expand the solute
______
2. Overcome IMF in solvent to make room for the solute
Expand the solvent
______
3. Solute/Solvent interaction
·
Heat of solution ΔHsoln
• Overall endothermic =
o Feels cold to the touch
• Overall exothermic =
o Feels warm to the touch
FACTORS affecting SOLUBILITY
1. Structural effects
o “Likes dissolve likes”
• Polar substances are more soluble in polar solvents.
• Hydrophillic – water loving
o Ionic and polar covalent compounds
• Hydrophobic – water fearing
o Non-polar substances
Which of the following would be miscible (mutually soluble)?
C6H6 H20 MgCl2 CH3OH I2 C3H7OH
2. Pressure
Has little effect on solid or liquid solubility.
Higher pressure ______the solubility of a gas.
Henry’s law
P = partial pressure of the gas above the solution
K = constant for a particular solution
C = concentration of dissolved gas
• The amount of dissolved gas is ______to the pressure of the gas above the solution.
• This only applies to solutions where the gas does ______in the solvent.
Ex. The solubility of oxygen is 2.2x10-4 M at 0°C and 0.10 atm. Calculate the solubility at 0°C and 0.35 atm.
2. Temperature effects
FOR SOLIDS, dissolving always occurs ______at higher temperatures BUT
The amount of solute able to be dissolved may ______with the increased temperature.
Solubility (the total amount of solute that may be dissolved at a certain temperature) must be determined ______.
FOR GASES, solubility ______with increasing temperature.
Higher kinetic energy of the gas causes higher Pvap of the dissolved gas, more gas molecules escape the surface to the solvent and the gas becomes less soluble.
Everyday example:
Pvap OF SOLUTIONS
A non-volatile solute ______the vapor pressure of the solvent.
Molecules of the solute ______the surface of the solvent, making it harder for the solvent molecules to escape into the gas phase.
The number of particles is ______to the decrease in the amount of vapor pressure, so
______(which completely dissociate into ions) have a greater effect on the Pvap.
A volatile solute ______the vapor pressure of the solvent.
RAOULT’S LAW
Psoln = Xsolvent (P°solvent)
Psoln =
Xsolvent =
P°solvent =
Raoult’s law practice
Glycerine, C3H8O3 – a non volatile solute
What is the Psoln made by adding 164 g of glycerine to 338 ml of water at 39.8°C? Vapor pressure of
water is 54.74 torr at this temperature. Density of water is 0.992 g/ml
Raoult’s law with electrolytes
• 52.9 g CuCl2 (a strong electrolyte) is added to 800.0 ml of water at 52.0°C. Vapor pressure of water at this temperature is 102.1 torr and the density is .987 g/ml.
Hint: Write the dissociation reaction to determine the total number of moles of ions in solution.
Finding MM using Raoult’s law
29.6 °C P°H20 = 31.1 torr
86.7 grams of an unknown non-volatile, non-electrolyte is added to 350.0 g of water and the P soln = 28.6 torr. What is the molar mass of the substance?
VOLATILE SOLUTES
• Contribute to vapor pressure
• Ptotal = Psolute + Psolvent
• Ptotal = (Xsolute )(P°solute) + (Xsolvent)(P°solvent) (ideal)
Practice problem
• What is the vapor pressure when 58.9 g of hexane is mixed with 44.0 grams of benzene at 60.0°C?
o P° Hexane C6H14 60.0°C is 573 torr
o P° benzene C6H6 60.0°C is 391 torr
COLLIGATIVE PROPERTIES
• Boiling point elevation
• Freezing point depression
• Osmotic pressure
o A colligative property only depends on the ______, not the identity, of the solute particles.
BP ELEVATION
l A non-volatile solute ______the bp of the liquid
since the overall Psoln is ______)
o Recall that boiling occurs when ______
o bp elevation depends on the ______of the solute
o If the bp elevation is known, the ______of a solute may be determined.
BP ELEVATION
ΔT = i Kb msolute
o ΔT = bp elevation
o i = ______= number of ions that result from complete dissociation
o Kb is the bp elevation constant for a solvent
• Kb for H20 = 0.51 °C kg/mol
o msolute =
Practice problem
• What is the boiling point elevation if 31.65 g of NaCl is added to 220.0 ml of water at 34.0 °C if the density of water is 0.994 g/ml. Assume complete dissociation of NaCl.
FREEZING POINT DEPRESSION
The solvent must be cooled to a ______to form crystals since solute
particles are ______the solid formation.
ΔT = i Kf msolute
Kf H20 = -1.86 °C kg/mol
Practice problem
• How many grams of glycerin (C3H8O3) must be added to 350.0 grams of water to lower the freezing point to -3.84 °C?
Vant Hoff factor i
• i expected = the number of moles of ions that results from
______of a solute.
• Ex. NaCl à Na+ + Cl-
o i = 2
o But, i actually = 1.9
Why is it lower?
• Some ions in solution pair up momentarily – ______
• i = moles of particles in solution/ moles of solute dissolved
• Ion pairing is greater in solutions with ______since the ions will have a greater attraction for each other.
• Ex. FeCl3
o i expected = 4
o i observed = 3.4
OSMOSIS
Osmosis – flow of a ______into a solution through a semi-permeable membrane due to differences in solute concentration. Flows into a region with ______concentration.