Download CHAPTER 10 LIQUIDS and SOLIDS

CHAPTER 10 LIQUIDS and SOLIDS
INTERMOLECULAR FORCES


Forces between molecules that hold them together ________________________________.
Higher forces lead to higher _____________________ and ____________________ points.
 Dipole –dipole forces
 London dispersion forces
DIPOLE-DIPOLE FORCES
 Result when a __________________________________________________ of polar covalent
molecules attract.
 About _______________________________________ a covalent bond.
 Includes __________________________________

Indicated by _______________
 ____________________________________________________________
(ex. _____________________________) form strong interactions with the H.
 High intermolecular bond energy (________________________________)
LONDON DISPERSION FORCES (LDF)
 Exist in __________________________substances
Ex.
 Caused by _______________________________________ which arise due
to a ________________________________________.
 This leads to an ____________________________________ in other atoms and an
attraction arises between opposite poles.
 Known as ________________________________________
 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
 Why is it so low?

How does it prove that London forces exist?

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
 Low __________________________
 Lack of________________________
 More dense than ________________
SURFACE TENSION

Forms spherical droplets because of
______________________________________________________________ – minimizes
surface area
 Higher molecular force  _________________________________________
CAPILLARY ACTION
 ________________________________________ of a liquid up a tube.
 Why would mercury form a convex meniscus and water a concave miniscus?

___________________________________________________ – intermolecular force between
the molecules of the liquid.

________________________________________________ – force between the liquid and the
container
 Glass has ______________________________
So, which liquid is more attracted to the glass? What does this do to the shape of the meniscus?
VISCOSITY
 A measure of the liquid’s _________________________________________.
 Higher intermolecular forces
= ___________________________________________________
 ___________________________________________________________ because the molecules
get “tangled” in one another.
VAPOR PRESSURE
 Liquid in a closed container _____________________________________
and ___________________________________ continuously until an
_______________________________________is reached.
(_____________________________________________________________)
 known as the ________________________________________________of the liquid.
 Vapor pressure _______________________________________________
because molecules have more ________________________________ can
escape into the gas phase easily.
HIGH VAPOR PRESSURE
 __________________________ – evaporate easily from an open container.
 ___________________________________ intermolecular forces
 More molecules ________________________________________________
LOW VAPOR PRESSURE
 ____________________________________________
 Large number of ______________________________________________________ holding
the molecules together in the liquid phase.
 Higher ___________________________________________(more
London
dispersion forces)
RELATING VAPOR PRESSURE TO TEMPERATURE
 _____________________________________________ equation
 Relates temperature, Enthalpy of vaporization, and the vapor pressure at different
temperatures.
 Uses the gas constant ___________________________ or
_________________________.

SAMPLE PROBLEMS
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.
 Which has greater surface tension N2 or Br2?
PHASE DIAGRAMS
 Represent the phases of a substance as a function of ________________________and
___________________________.
 Any _____________________________ can be represented using a phase diagram.
 Sometimes _______________________________are also represented.
POINTS of INTEREST ON A PHASE DIAGRAM
 Normal melting point – the temperature at which the _____________________ phase when
the atmospheric pressure = ____________________________________.
 Normal boiling point – the temperature at which the ______________________ phase when
the atmospheric pressure = _____________________________.
 Triple point – the temperature and pressure at which
_____________________________________ coexist
 Critical point – the temperature beyond which the ___________________________ cannot
exist.
PHASE CHANGES
Melting
Freezing
Sublimation
Deposition
Vaporization
Condensation
H2O PHASE DIAGRAM
Normal melting point:
Normal boiling point:
Triple point:
Critical point:
S/L line back slant indicates
the L phase is more dense –
exists at higher pressures.
CO2 PHASE DIAGRAM
What does CO2 do when heated at 1
atm pressure?
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
 Electron sea remains so alloys will still _________________________.
 __________________________________ – smaller atoms fill interstitial spaces between the
large atoms.
o Ex. Steel _____________________________
o ___________________________________ usually increases
o Rigidity increases

malleability and ductility reduces
 _________________________________________ – 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)
 Elements ex. ________________________________________________
 Compounds ex. ______________________________________________
1. High melting points
 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
 Conductivity increases with temperature
 N-type doping – _______________________________ carrying due to adding
an element with an extra valence electron (ex. P)
 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
 Because electrons are bound within the __________________________ of each molecule
within the solid.
2. Low ____________________________________
 due to only ___________________________ existing between the particles
IONIC
Conduct in solid state
Conduct when melted
Yes
Conduct when in aq
solution
Yes
Melting point
High
Rigid
Brittle
Other distinct features
METALLIC COVALENT NETWORK
Yes
Si semiconductor
Yes
Si semiconductor
Wide
range
Malleable/
ductile
Extremely high
Can be
alloyed
MOLECULAR
Low
Hard
Exception: graphite
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 ( 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 H CO to 100.0 g of water. The final volume of
2
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 ΔH
soln
•
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.
-4
Ex. The solubility of oxygen is 2.2x10 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 P
vap
of the dissolved gas, more gas molecules
escape the surface to the solvent and the gas becomes less soluble.
Everyday example:
P
vap
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 P .
vap
 A volatile solute __________________________________ the vapor pressure of the solvent.
RAOULT’S LAW
P
P
soln
soln
X
=X
solvent
)
=
solvent
P°
(P°
solvent
=
solvent
=
Raoult’s law practice
Glycerine, C H O – a non volatile solute
3
8
What is the P
soln
3
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°
= 31.1 torr
H20
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
• P
=P
+P
total
•
P
total
solute
= (X
solute
solvent
)(P°
) + (X
solute
solvent
)(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
 A non-volatile solute ___________________________________________ the bp of the liquid
since the overall P
soln
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 K m
b
solute
o ΔT = bp elevation
o i = __________________________________________ = number of ions that result
from complete dissociation
o K is the bp elevation constant for a solvent
b
•
o m
solute
K for H 0 = 0.51 °C kg/mol
b
2
=
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 K m
f
solute
 K H 0 = -1.86 °C kg/mol
f
2
Practice problem
• How many grams of glycerin (C H O ) must be added to 350.0 grams of water to lower the
3
8
3
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  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. FeCl
•
3
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.
 _______________________ – higher pressure than the surrounding solution due to higher
solute concentration.
 _______________________ – lower solute concentration and pressure than the surrounding
solution.
 _______________________– solutions with identical osmotic pressures.
OSMOTIC PRESSURE
 Osmotic pressure – the pressure that just stops osmosis.
 Measured in _____________________________________________
 Can be used to find ____________________________________________
 More accurate than bp or fp detemination
=iMRT
=
i = vant Hoff factor
M=
R = 0.0821 Latm/mol K
T = Kelvin temperature
Practice problem
• The osmotic pressure of a solution of 26.5 mg of aspartame per L is 1.70 torr @ 30.0 °C. What
is the molar mass of aspartame?
Everyday example
 _____________________________________________ reverse osmosis.
 Apply a pressure __________________________________________________ than the
osmotic pressure to a solution of salt water and the ______________________________ will
pass through the semi-permeable membrane towards the pure solvent side.