Liquids and Solids

Report
Liquids and Solids
Chapter 16
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Liquids and Solids – ch. 16
Liquids and Solids – ch. 16
1. Indicate the types of forces present and the type of solid for each of
the following substances:
a. CCl4
h. KOH
b. HF
i. BH3
c. NH4Br
j. H2CO
d. F2
k. SiO2
e. CH3OH
l. Ar
f. Ca
m. P
g. H2S
n. S8
Liquids and Solids – ch. 16
Dipole-Dipole
Hydrogen Bonding
Only for molecules with
dipole moments aka
polar molecules
A particularly strong
dipole-dipole
only for molecules
with hydrogen
bonded to O, N or F
London Dispersion Forces
Liquids and Solids – ch. 16
2. Using intermolecular forces predict the following:
a. highest melting point
F2 or Br2
b. highest melting point
HF or HCl
c. highest boiling point
HOCH2CH2OH or CH3CH2OH
d. highest boiling point
CH3CH3 or CH3CH2CH3
e. highest vapor pressure CH3CH2OH or CH3OCH3
f. highest vapor pressure CCl4 or CH2Cl2
g. highest freezing point MgO or H2O
h. highest surface tension C14H30 or C24H50
Liquids and Solids – ch. 16
Relative strength of forces ⇒ Ionic > >> Hydrogen bonding > Dipole-Dipole > Dispersion
for molecules comparable in size
Dispersion Forces
1. Increase with molecular size
2. Decrease with the
degree of branching
ex:
As the attractive forces get stronger…
1. Boiling point ↑
2. Freezing point ↑
3. Melting point ↑
4. Heat of fusion ↑
5. Heat of vaporization ↑
6. Viscosity ↑
7. Surface Tension ↑
8. Vapor Pressure ↓
9. Volatility ↓
Liquids and Solids – ch. 16
Liquids and Solids – ch. 16
3. Copper has an inter-planar spacing of 1.36 Å. Calculate the
wavelength of the X ray that should be used if θ is 15° (assume
n=1).
Liquids and Solids – ch. 16
Liquids and Solids – ch. 16
4 Types of Unit Cells for Metallic solids
1. Simple Cubic:
1 atom/unit cell
3. Face-centered
Cubic or Cubic
Closest Packed: 4
atoms/unit cell
abc hexagonal
alignment of
atoms
2. Body-centered
Cubic: 2
atoms/unit cell
4. Hexagonal
Closest Packed: 2
atoms/unit cell
abab hexagonal
alignment of
atoms
Liquids and Solids – ch. 16
2 Types of closest packing
1. abab – hexagonal closest packed
2. abca – cubic closest packed
Liquids and Solids – ch. 16
Counting Atoms in a Cubic Unit Cell
Atom is shared
between 2 unit cells
Atom is shared
between 4 unit cells
Atom is shared
between 8 unit cells
Liquids and Solids – ch. 16
Unit Cell
Simple Cubic
Number of
atoms/unit cell – (%
by volume)
1
(52.4%)
Coordination
Number
Edge Length as a
function of atomic
radius
6
e = 2r
=
4
Body Centered
Cubic
2
(68%)
8
Face Centered
Cubic aka Cubic
Closest Packed
4
(74%)
12
= 8
(e = 2.828r)
12
N/A
Hexagonal Closest
Packed
2
(74%)
3
(e = 2.309r)
Liquids and Solids – ch. 16
4. Zinc crystallizes in a cubic closest packed structure. The radius of a
zinc atom is 135 pm. Calculate the density in g/mL for solid zinc.
Liquids and Solids – ch. 16
5. Titanium metal has a body-centered cubic unit cell. The density is
4.50 g/cm3. Calculate the atomic radius in angstroms of titanium.
(1010Å= 1m)
Liquids and Solids – ch. 16
6. Consider the following cubic closest packed structures. For each
compound determine where the ions are in the lattice.
a. NaCl (Na+ = 95 pm, Cl– = 181 pm )
b. ZnS (Zn2+= 74 pm, S2– = 184 pm)
c. CaCl2 (Ca2+ = 99 pm, Cl– = 181 pm)
Liquids and Solids – ch. 16
Ionic Solids
Anions (or the larger ion) will align themselves in the
lattice points of the unit cell
Cations (or the smaller ion) will occupy the holes created
by the lattice points
In FCC aka CCP lattices there are 3 types of holes:
a. Trigonal holes are occupied when the radius of the
cation is less than 22% of the anion – very rare
b. Tetrahedral holes (8 available) are occupied when the
radius of the cation is between 22% and 41% of the
anion
c. Octahedral holes (4 available) are occupied when the
radius of the cation is between 41% and 73% of the
anion
Liquids and Solids – ch. 16
7. Identify the type of doping in each of the following.
a. Gallium doped with tin
b. Antimony doped with germanium
c. A material is made from Al, Ga, and As. The mole fractions of
these elements are 0.25, 0.26, and 0.49, respectively.
Liquids and Solids – ch. 16
Doping ⇒
enhancing the conductivity
of a semiconductor
by adding a trace amount of
an impurity (aka the dope)
2 Different Types of doping:
a. n-type ⇒ impurity has
more valence electrons in a
valence shell with higher energy
than the semiconductor
b. p-type impurity has
fewer valence electrons in a
valence shell with lower energy
than the semiconductor
Si has 4 valence electrons
As (the dope)
has 5 valence electrons
Si has 4 valence electrons
B (the dope)
has 3 valence electrons
Liquids and Solids – ch. 16
M.O. model
illustrating doping
and how it enhances
conductivity
n-type doping
p-type doping
Liquids and Solids – ch. 16
8. Consider the following phase diagrams for water and carbon dioxide
respectively – which phase is the most dense for each substance?
How does pressure affect the MP and BP for each substance?
Liquids and Solids – ch. 16
pressure
melting
Solid
freezing
Liquid
vaporization
condensation
Equilibrium lines
sublimation
deposition
Gas
temperature
Liquids and Solids – ch. 16
9. Pure compound Z has a triple point at 18 ° C and 72 torr, a normal
melting point at 21 °C, and a normal boiling point at 87 °C.
Which of the following statements regarding compound Z
is/are correct?
a. The density of the solid is greater that that of the liquid.
b. Sublimation occurs if starting with a solid at a constant
temperature of 17 °C the pressure is decreased until a
phase change occurs.
c. Condensation occurs if the temperature is decreased from
55 °C to 13 °C at a constant pressure of 1.00 atm.
Liquids and Solids – ch. 16
10. The enthalpy of vaporization for water is 44 kJ/mol. What is the
boiling point if the atmospheric pressure were 0.33 atm?
ln P2 = −ΔHvap 1 − 1
P1
R
T2
T1
Liquids and Solids – ch. 16
11. How much heat does is required to take 10 g of ice at -31 °C to
vapor at 155 °C? (Csolid = 2.03 J/g°C , Cliquid = 4.18 J/g°C , Cgas =
2.02 J/g°C, ΔHfus = 6.01 kJ/mol, and ΔHvap = 40.7 kJ/mol)
Liquids and Solids – ch. 16
Heating
curve
for water
q = n Δ Hfus
q = n Δ Hvap
q = mcΔT
Liquids and Solids – ch. 16
12. Determine the final temperature if a 25 g cube of ice at -7 °C is
placed in 180 mL of water at 64 °C and allowed to come to
equilibrium. (Csolid = 2.03 J/g°C , Cliquid = 4.18 J/g°C , Cgas = 2.02
J/g°C, ΔHfus = 6.01 kJ/mol, and ΔHvap = 40.7 kJ/mol)
Liquids and Solids – Answer Key
1. Indicate the types of forces present for each of the following:
a. CCl4 => dispersion b. HF => H-bonding and dispersion
c. NH4Br => ionic d. F2 => dispersion e. CH3OH => H-bonding,
dipole-dipole and dispersion f. H2S => dipole-dipole and
dispersion g. KOH => ionic h. BH3 => dispersion
i. H2CO => dipole-dipole and dispersion
2. Using intermolecular forces predict the following:
a. Br2 b. HF c. HOCH2CH2OH d. CH3CH2CH3 e. NH3
f. CCl4 g. MgO h. C24H50
3. Copper has an inter-planar spacing of 1.36 Å. Calculate the
wavelength of the X ray that should be used if θ is 15° (assume
n=1).
nλ=2dsinθ => (1)(λ)=2(1.36 Å)(sin 15°) => λ = 0.70 Å or 7nm
Liquids and Solids – Answer Key
4. Zinc crystallizes in a cubic closest packed structure. The radius of a zinc
atom is 135 pm. Calculate the density in g/mL for solid zinc.
D = mass/volume => since cubic closest packed has 4 atoms per unit cell =>
mass of unit cell = 4(65.39amu)(1g/6.022x1023amu) = 4.34x10-22g
The volume of the unit cell is edge3 => e3=(2.828(1.35x10-8cm)) 3 => 5.57x1023cm3
D = (4.34x10-22g)/(5.57x10-23cm3) = 7.8g/cm3
5. Titanium metal has a body-centered cubic unit cell. The density is 4.50
g/cm3. Calculate the atomic radius of titanium. Body centered cubic has 2
atoms per unit cell => mass of unit cell = 2(47.88amu)(1g/6.022x1023amu)
= 1.59x10-22g => volume = m/d => volume = (1.59x10-22g)/(4.5g/cm3) =
3.53x10-23 cm3 => edge = (3.53x10-23 cm3 )1/3 = 3.29x10-8cm or 329pm =>
radius = 329pm/2.309 = 142pm
Liquids and Solids – Answer Key
6. Compare the cubic closest packed structures for NaCl (radius of Na+
= 0.66 radius of Cl-), ZnS (radius of Zn2+ = 0.35 radius of S2-) and
CaCl2 (radius of Ca2+ = 0.68 radius of Cl-).
NaCl => Na+ will fill all of the octahedral holes
ZnS => Zn2+ will fill all of the ½ of the tetrahedral holes
CaCl2 => Ca2+ will fill ½ of the octahedral holes
7. Identify the type of doping in each of the following.
a. Ga/Sn => n-type b. Si/B => p-type
8. What type of solid would you expect each of the following to form?
a. KBr ionic b. H2S molecular c. SiO2 covalent network
d. Pb atomic/metallic e. P atomic/covalent network
f. Xe atomic g. CO2 molecular
Liquids and Solids – Answer Key
9.
Carbon dioxide
Water
Liquids and Solids – Answer Key
10. The enthalpy of vaporization for water is 44 kJ/mol. What is the
boiling point if the atmospheric pressure were 0.33 atm? Since we
know that the BP of water at 1 atm is 100°C we can figure out the
BP at all other pressures using the ΔHvap
ln(P1/P2) = (ΔHvap/R)(T2-1 – T1-1)
ln(0.33atm/1atm) = (44kJ/mol/0.008314kJ/molK)(T2-1 – 373-1K)
T2 = 405K
11. How much heat does is required to take 10 g of ice at -31 °C to vapor
at 155 °C? (Csolid = 2.03 J/g°C , Cliquid = 4.18 J/g°C , Cgas = 2.02 J/g°C,
ΔHfus = 6.01 kJ/mol, and ΔHvap = 40.7 kJ/mol)
This is a 5 step process => 3 changes in temperature (q=mC Δ T)
and 2 phase changes (q=n ΔH)
Liquids and Solids – Answer Key
q1=(10g)(2.03 J/g°C)(+31°C) = 629.3J or 0.629kJ
q2=(10g/18g/mol)(6.01kJ/mol) = 3.34kJ
q3=(10g)(4.18 J/g°C)(+100°C) = 4180J or 4.18kJ
q4=(10g/18g/mol)(40.7 kJ/mol) = 22.6kJ
q5=(10g)(2.02 J/g°C)(+55°C) = 1.11kJ
qtotal = 31.86kJ
12. Determine the final temperature if a 25 g cube of ice at -7 °C is
placed in 180 mL of water at 64 °C and allowed to come to
equilibrium. (Csolid = 2.03 J/g°C , Cliquid = 4.18 J/g°C , Cgas = 2.02
J/g°C, ΔHfus = 6.01 kJ/mol, and ΔHvap = 40.7 kJ/mol)
Heat is transferred from the hot water into the cold water
-qhot = +qcold
Liquids and Solids – Answer Key
-mCΔT = mCsolid Δ T + nHfus +mCliquidΔ T
-(180g)(4.18J/g°C)(Tf-64°C)
=(25g)(2.03J/g°C)(7°C)+(25g/18g/mol)(6010J/mol)+(25g)(4.18J/g°C)(Tf-0°C)
Tf = 46°C

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